On Thu, Sep 05, 2024 at 04:51:22PM +0200, Antonino Maniscalco wrote:
> This patch implements preemption feature for A6xx targets, this allows
> the GPU to switch to a higher priority ringbuffer if one is ready. A6XX
> hardware as such supports multiple levels of preemption granularities,
> ranging from coarse grained(ringbuffer level) to a more fine grained
> such as draw-call level or a bin boundary level preemption. This patch
> enables the basic preemption level, with more fine grained preemption
> support to follow.
>
> Signed-off-by: Sharat Masetty <smase...@codeaurora.org>
> Signed-off-by: Antonino Maniscalco <antomani...@gmail.com>
> Tested-by: Neil Armstrong <neil.armstr...@linaro.org> # on SM8650-QRD
> ---
> drivers/gpu/drm/msm/Makefile | 1 +
> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 293 +++++++++++++++++++++-
> drivers/gpu/drm/msm/adreno/a6xx_gpu.h | 161 ++++++++++++
> drivers/gpu/drm/msm/adreno/a6xx_preempt.c | 391
> ++++++++++++++++++++++++++++++
> drivers/gpu/drm/msm/msm_ringbuffer.h | 7 +
> 5 files changed, 844 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/Makefile b/drivers/gpu/drm/msm/Makefile
> index f5e2838c6a76..32e915109a59 100644
> --- a/drivers/gpu/drm/msm/Makefile
> +++ b/drivers/gpu/drm/msm/Makefile
> @@ -23,6 +23,7 @@ adreno-y := \
> adreno/a6xx_gpu.o \
> adreno/a6xx_gmu.o \
> adreno/a6xx_hfi.o \
> + adreno/a6xx_preempt.o \
>
> adreno-$(CONFIG_DEBUG_FS) += adreno/a5xx_debugfs.o \
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 32a4faa93d7f..ed0b138a2d66 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -16,6 +16,83 @@
>
> #define GPU_PAS_ID 13
>
> +/* IFPC & Preemption static powerup restore list */
> +static const uint32_t a7xx_pwrup_reglist[] = {
> + REG_A6XX_UCHE_TRAP_BASE,
> + REG_A6XX_UCHE_TRAP_BASE + 1,
> + REG_A6XX_UCHE_WRITE_THRU_BASE,
> + REG_A6XX_UCHE_WRITE_THRU_BASE + 1,
> + REG_A6XX_UCHE_GMEM_RANGE_MIN,
> + REG_A6XX_UCHE_GMEM_RANGE_MIN + 1,
> + REG_A6XX_UCHE_GMEM_RANGE_MAX,
> + REG_A6XX_UCHE_GMEM_RANGE_MAX + 1,
> + REG_A6XX_UCHE_CACHE_WAYS,
> + REG_A6XX_UCHE_MODE_CNTL,
> + REG_A6XX_RB_NC_MODE_CNTL,
> + REG_A6XX_RB_CMP_DBG_ECO_CNTL,
> + REG_A7XX_GRAS_NC_MODE_CNTL,
> + REG_A6XX_RB_CONTEXT_SWITCH_GMEM_SAVE_RESTORE,
> + REG_A6XX_UCHE_GBIF_GX_CONFIG,
> + REG_A6XX_UCHE_CLIENT_PF,
REG_A6XX_TPL1_DBG_ECO_CNTL1 here. A friendly warning, missing a register
in this list (and the below list) will lead to a very frustrating debug.
> +};
> +
> +static const uint32_t a7xx_ifpc_pwrup_reglist[] = {
> + REG_A6XX_TPL1_NC_MODE_CNTL,
> + REG_A6XX_SP_NC_MODE_CNTL,
> + REG_A6XX_CP_DBG_ECO_CNTL,
> + REG_A6XX_CP_PROTECT_CNTL,
> + REG_A6XX_CP_PROTECT(0),
> + REG_A6XX_CP_PROTECT(1),
> + REG_A6XX_CP_PROTECT(2),
> + REG_A6XX_CP_PROTECT(3),
> + REG_A6XX_CP_PROTECT(4),
> + REG_A6XX_CP_PROTECT(5),
> + REG_A6XX_CP_PROTECT(6),
> + REG_A6XX_CP_PROTECT(7),
> + REG_A6XX_CP_PROTECT(8),
> + REG_A6XX_CP_PROTECT(9),
> + REG_A6XX_CP_PROTECT(10),
> + REG_A6XX_CP_PROTECT(11),
> + REG_A6XX_CP_PROTECT(12),
> + REG_A6XX_CP_PROTECT(13),
> + REG_A6XX_CP_PROTECT(14),
> + REG_A6XX_CP_PROTECT(15),
> + REG_A6XX_CP_PROTECT(16),
> + REG_A6XX_CP_PROTECT(17),
> + REG_A6XX_CP_PROTECT(18),
> + REG_A6XX_CP_PROTECT(19),
> + REG_A6XX_CP_PROTECT(20),
> + REG_A6XX_CP_PROTECT(21),
> + REG_A6XX_CP_PROTECT(22),
> + REG_A6XX_CP_PROTECT(23),
> + REG_A6XX_CP_PROTECT(24),
> + REG_A6XX_CP_PROTECT(25),
> + REG_A6XX_CP_PROTECT(26),
> + REG_A6XX_CP_PROTECT(27),
> + REG_A6XX_CP_PROTECT(28),
> + REG_A6XX_CP_PROTECT(29),
> + REG_A6XX_CP_PROTECT(30),
> + REG_A6XX_CP_PROTECT(31),
> + REG_A6XX_CP_PROTECT(32),
> + REG_A6XX_CP_PROTECT(33),
> + REG_A6XX_CP_PROTECT(34),
> + REG_A6XX_CP_PROTECT(35),
> + REG_A6XX_CP_PROTECT(36),
> + REG_A6XX_CP_PROTECT(37),
> + REG_A6XX_CP_PROTECT(38),
> + REG_A6XX_CP_PROTECT(39),
> + REG_A6XX_CP_PROTECT(40),
> + REG_A6XX_CP_PROTECT(41),
> + REG_A6XX_CP_PROTECT(42),
> + REG_A6XX_CP_PROTECT(43),
> + REG_A6XX_CP_PROTECT(44),
> + REG_A6XX_CP_PROTECT(45),
> + REG_A6XX_CP_PROTECT(46),
> + REG_A6XX_CP_PROTECT(47),
> + REG_A6XX_CP_AHB_CNTL,
> +};
> +
> +
> static inline bool _a6xx_check_idle(struct msm_gpu *gpu)
> {
> struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> @@ -68,6 +145,8 @@ static void update_shadow_rptr(struct msm_gpu *gpu, struct
> msm_ringbuffer *ring)
>
> static void a6xx_flush(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
> {
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> uint32_t wptr;
> unsigned long flags;
>
> @@ -81,12 +160,26 @@ static void a6xx_flush(struct msm_gpu *gpu, struct
> msm_ringbuffer *ring)
> /* Make sure to wrap wptr if we need to */
> wptr = get_wptr(ring);
>
> - spin_unlock_irqrestore(&ring->preempt_lock, flags);
> -
> /* Make sure everything is posted before making a decision */
> mb();
This looks unnecessary.
>
> - gpu_write(gpu, REG_A6XX_CP_RB_WPTR, wptr);
> + /* Update HW if this is the current ring and we are not in preempt*/
> + if (!a6xx_in_preempt(a6xx_gpu)) {
> + /*
> + * Order the reads of the preempt state and cur_ring. This
> + * matches the barrier after writing cur_ring.
> + */
> + rmb();
we can use the lighter smp variant here.
> +
> + if (a6xx_gpu->cur_ring == ring)
> + gpu_write(gpu, REG_A6XX_CP_RB_WPTR, wptr);
> + else
> + ring->skip_inline_wptr = true;
> + } else {
> + ring->skip_inline_wptr = true;
> + }
> +
> + spin_unlock_irqrestore(&ring->preempt_lock, flags);
> }
>
> static void get_stats_counter(struct msm_ringbuffer *ring, u32 counter,
> @@ -138,12 +231,14 @@ static void a6xx_set_pagetable(struct a6xx_gpu
> *a6xx_gpu,
set_pagetable checks "cur_ctx_seqno" to see if pt switch is needed or
not. This is currently not tracked separately for each ring. Can you
please check that?
I wonder why that didn't cause any gpu errors in testing. Not sure if I
am missing something.
>
> /*
> * Write the new TTBR0 to the memstore. This is good for debugging.
> + * Needed for preemption
> */
> - OUT_PKT7(ring, CP_MEM_WRITE, 4);
> + OUT_PKT7(ring, CP_MEM_WRITE, 5);
> OUT_RING(ring, CP_MEM_WRITE_0_ADDR_LO(lower_32_bits(memptr)));
> OUT_RING(ring, CP_MEM_WRITE_1_ADDR_HI(upper_32_bits(memptr)));
> OUT_RING(ring, lower_32_bits(ttbr));
> - OUT_RING(ring, (asid << 16) | upper_32_bits(ttbr));
> + OUT_RING(ring, upper_32_bits(ttbr));
> + OUT_RING(ring, ctx->seqno);
>
> /*
> * Sync both threads after switching pagetables and enable BR only
> @@ -268,6 +363,43 @@ static void a6xx_submit(struct msm_gpu *gpu, struct
> msm_gem_submit *submit)
> a6xx_flush(gpu, ring);
> }
>
> +static void a6xx_emit_set_pseudo_reg(struct msm_ringbuffer *ring,
> + struct a6xx_gpu *a6xx_gpu, struct msm_gpu_submitqueue *queue)
> +{
> + u64 preempt_offset_priv_secure;
> +
> + OUT_PKT7(ring, CP_SET_PSEUDO_REG, 15);
> +
> + OUT_RING(ring, SMMU_INFO);
> + /* don't save SMMU, we write the record from the kernel instead */
> + OUT_RING(ring, 0);
> + OUT_RING(ring, 0);
> +
> + /* privileged and non secure buffer save */
> + OUT_RING(ring, NON_SECURE_SAVE_ADDR);
> + OUT_RING(ring, lower_32_bits(
> + a6xx_gpu->preempt_iova[ring->id] +
> PREEMPT_OFFSET_PRIV_NON_SECURE));
> + OUT_RING(ring, upper_32_bits(
> + a6xx_gpu->preempt_iova[ring->id] +
> PREEMPT_OFFSET_PRIV_NON_SECURE));
> + OUT_RING(ring, SECURE_SAVE_ADDR);
> + preempt_offset_priv_secure =
> +
> PREEMPT_OFFSET_PRIV_SECURE(a6xx_gpu->base.info->preempt_record_size);
> + OUT_RING(ring, lower_32_bits(
> + a6xx_gpu->preempt_iova[ring->id] + preempt_offset_priv_secure));
> + OUT_RING(ring, upper_32_bits(
> + a6xx_gpu->preempt_iova[ring->id] + preempt_offset_priv_secure));
> +
> + /* user context buffer save, seems to be unnused by fw */
> + OUT_RING(ring, NON_PRIV_SAVE_ADDR);
> + OUT_RING(ring, 0);
> + OUT_RING(ring, 0);
> +
> + OUT_RING(ring, COUNTER);
> + /* seems OK to set to 0 to disable it */
> + OUT_RING(ring, 0);
> + OUT_RING(ring, 0);
> +}
> +
> static void a7xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
> {
> unsigned int index = submit->seqno % MSM_GPU_SUBMIT_STATS_COUNT;
> @@ -283,6 +415,13 @@ static void a7xx_submit(struct msm_gpu *gpu, struct
> msm_gem_submit *submit)
> OUT_PKT7(ring, CP_THREAD_CONTROL, 1);
> OUT_RING(ring, CP_THREAD_CONTROL_0_SYNC_THREADS | CP_SET_THREAD_BR);
>
> + /*
> + * If preemption is enabled, then set the pseudo register for the save
> + * sequence
> + */
> + if (gpu->nr_rings > 1)
> + a6xx_emit_set_pseudo_reg(ring, a6xx_gpu, submit->queue);
Can we move this after set_pagetable()?
> +
> a6xx_set_pagetable(a6xx_gpu, ring, submit->queue->ctx);
>
> get_stats_counter(ring, REG_A7XX_RBBM_PERFCTR_CP(0),
> @@ -376,6 +515,8 @@ static void a7xx_submit(struct msm_gpu *gpu, struct
> msm_gem_submit *submit)
> OUT_RING(ring, upper_32_bits(rbmemptr(ring, bv_fence)));
> OUT_RING(ring, submit->seqno);
>
> + a6xx_gpu->last_seqno[ring->id] = submit->seqno;
> +
> /* write the ringbuffer timestamp */
> OUT_PKT7(ring, CP_EVENT_WRITE, 4);
> OUT_RING(ring, CACHE_CLEAN | CP_EVENT_WRITE_0_IRQ | BIT(27));
> @@ -389,10 +530,32 @@ static void a7xx_submit(struct msm_gpu *gpu, struct
> msm_gem_submit *submit)
> OUT_PKT7(ring, CP_SET_MARKER, 1);
> OUT_RING(ring, 0x100); /* IFPC enable */
>
> + /* If preemption is enabled */
> + if (gpu->nr_rings > 1) {
> + /* Yield the floor on command completion */
> + OUT_PKT7(ring, CP_CONTEXT_SWITCH_YIELD, 4);
> +
> + /*
> + * If dword[2:1] are non zero, they specify an address for
> + * the CP to write the value of dword[3] to on preemption
> + * complete. Write 0 to skip the write
> + */
> + OUT_RING(ring, 0x00);
> + OUT_RING(ring, 0x00);
> + /* Data value - not used if the address above is 0 */
> + OUT_RING(ring, 0x01);
> + /* generate interrupt on preemption completion */
> + OUT_RING(ring, 0x00);
> + }
> +
> +
> trace_msm_gpu_submit_flush(submit,
> gpu_read64(gpu, REG_A6XX_CP_ALWAYS_ON_COUNTER));
>
> a6xx_flush(gpu, ring);
> +
> + /* Check to see if we need to start preemption */
> + a6xx_preempt_trigger(gpu);
> }
>
> static void a6xx_set_hwcg(struct msm_gpu *gpu, bool state)
> @@ -588,6 +751,89 @@ static void a6xx_set_ubwc_config(struct msm_gpu *gpu)
> adreno_gpu->ubwc_config.min_acc_len << 23 | hbb_lo << 21);
> }
>
> +static void a7xx_patch_pwrup_reglist(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + struct adreno_reglist_list reglist[2];
> + void *ptr = a6xx_gpu->pwrup_reglist_ptr;
> + struct cpu_gpu_lock *lock = ptr;
> + u32 *dest = (u32 *)&lock->regs[0];
> + int i, j;
> +
This sequence is required only once. We can use a flag to check and bail out
next time.
> + lock->gpu_req = lock->cpu_req = lock->turn = 0;
> + lock->ifpc_list_len = ARRAY_SIZE(a7xx_ifpc_pwrup_reglist);
> + lock->preemption_list_len = ARRAY_SIZE(a7xx_pwrup_reglist);
> +
> + /* Static IFPC-only registers */
> + reglist[0].regs = a7xx_ifpc_pwrup_reglist;
> + reglist[0].count = ARRAY_SIZE(a7xx_ifpc_pwrup_reglist);
> + lock->ifpc_list_len = reglist[0].count;
> +
> + /* Static IFPC + preemption registers */
> + reglist[1].regs = a7xx_pwrup_reglist;
> + reglist[1].count = ARRAY_SIZE(a7xx_pwrup_reglist);
> + lock->preemption_list_len = reglist[1].count;
> +
> + /*
> + * For each entry in each of the lists, write the offset and the current
> + * register value into the GPU buffer
> + */
> + for (i = 0; i < 2; i++) {
> + const u32 *r = reglist[i].regs;
> +
> + for (j = 0; j < reglist[i].count; j++) {
> + *dest++ = r[j];
> + *dest++ = gpu_read(gpu, r[j]);
> + }
> + }
> +
> + /*
> + * The overall register list is composed of
> + * 1. Static IFPC-only registers
> + * 2. Static IFPC + preemption registers
> + * 3. Dynamic IFPC + preemption registers (ex: perfcounter selects)
> + *
> + * The first two lists are static. Size of these lists are stored as
> + * number of pairs in ifpc_list_len and preemption_list_len
> + * respectively. With concurrent binning, Some of the perfcounter
> + * registers being virtualized, CP needs to know the pipe id to program
> + * the aperture inorder to restore the same. Thus, third list is a
> + * dynamic list with triplets as
> + * (<aperture, shifted 12 bits> <address> <data>), and the length is
> + * stored as number for triplets in dynamic_list_len.
> + */
> + lock->dynamic_list_len = 0;
> +}
> +
> +static int a7xx_preempt_start(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + struct msm_ringbuffer *ring = gpu->rb[0];
> +
> + if (gpu->nr_rings <= 1)
> + return 0;
> +
> + /* Turn CP protection off */
> + OUT_PKT7(ring, CP_SET_PROTECTED_MODE, 1);
> + OUT_RING(ring, 0);
> +
> + a6xx_emit_set_pseudo_reg(ring, a6xx_gpu, NULL);
> +
> + /* Yield the floor on command completion */
> + OUT_PKT7(ring, CP_CONTEXT_SWITCH_YIELD, 4);
> + OUT_RING(ring, 0x00);
> + OUT_RING(ring, 0x00);
> + OUT_RING(ring, 0x01);
Looks like kgsl use 0x00 here. Not sure if that matters!
> + /* Generate interrupt on preemption completion */
> + OUT_RING(ring, 0x00);
> +
> + a6xx_flush(gpu, ring);
> +
> + return a6xx_idle(gpu, ring) ? 0 : -EINVAL;
> +}
> +
> static int a6xx_cp_init(struct msm_gpu *gpu)
> {
> struct msm_ringbuffer *ring = gpu->rb[0];
> @@ -619,6 +865,8 @@ static int a6xx_cp_init(struct msm_gpu *gpu)
>
> static int a7xx_cp_init(struct msm_gpu *gpu)
> {
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> struct msm_ringbuffer *ring = gpu->rb[0];
> u32 mask;
>
> @@ -626,6 +874,8 @@ static int a7xx_cp_init(struct msm_gpu *gpu)
> OUT_PKT7(ring, CP_THREAD_CONTROL, 1);
> OUT_RING(ring, BIT(27));
>
> + a7xx_patch_pwrup_reglist(gpu);
> +
Looks out of place. I guess you kept it here to avoid an extra a7x
check. At least we should move this before the above pm4 packets.
> OUT_PKT7(ring, CP_ME_INIT, 7);
>
> /* Use multiple HW contexts */
> @@ -656,11 +906,11 @@ static int a7xx_cp_init(struct msm_gpu *gpu)
>
> /* *Don't* send a power up reg list for concurrent binning (TODO) */
> /* Lo address */
> - OUT_RING(ring, 0x00000000);
> + OUT_RING(ring, lower_32_bits(a6xx_gpu->pwrup_reglist_iova));
> /* Hi address */
> - OUT_RING(ring, 0x00000000);
> + OUT_RING(ring, upper_32_bits(a6xx_gpu->pwrup_reglist_iova));
> /* BIT(31) set => read the regs from the list */
> - OUT_RING(ring, 0x00000000);
> + OUT_RING(ring, BIT(31));
>
> a6xx_flush(gpu, ring);
> return a6xx_idle(gpu, ring) ? 0 : -EINVAL;
> @@ -784,6 +1034,16 @@ static int a6xx_ucode_load(struct msm_gpu *gpu)
> msm_gem_object_set_name(a6xx_gpu->shadow_bo, "shadow");
> }
>
> + a6xx_gpu->pwrup_reglist_ptr = msm_gem_kernel_new(gpu->dev, PAGE_SIZE,
> + MSM_BO_WC |
> MSM_BO_MAP_PRIV,
> + gpu->aspace,
> &a6xx_gpu->pwrup_reglist_bo,
> +
> &a6xx_gpu->pwrup_reglist_iova);
> +
> + if (IS_ERR(a6xx_gpu->pwrup_reglist_ptr))
> + return PTR_ERR(a6xx_gpu->pwrup_reglist_ptr);
> +
> + msm_gem_object_set_name(a6xx_gpu->pwrup_reglist_bo, "pwrup_reglist");
> +
> return 0;
> }
>
> @@ -1127,6 +1387,8 @@ static int hw_init(struct msm_gpu *gpu)
> if (a6xx_gpu->shadow_bo) {
> gpu_write64(gpu, REG_A6XX_CP_RB_RPTR_ADDR,
> shadowptr(a6xx_gpu, gpu->rb[0]));
> + for (unsigned int i = 0; i < gpu->nr_rings; i++)
> + a6xx_gpu->shadow[i] = 0;
> }
>
> /* ..which means "always" on A7xx, also for BV shadow */
> @@ -1135,6 +1397,8 @@ static int hw_init(struct msm_gpu *gpu)
> rbmemptr(gpu->rb[0], bv_rptr));
> }
>
> + a6xx_preempt_hw_init(gpu);
> +
> /* Always come up on rb 0 */
> a6xx_gpu->cur_ring = gpu->rb[0];
>
> @@ -1180,6 +1444,10 @@ static int hw_init(struct msm_gpu *gpu)
> out:
> if (adreno_has_gmu_wrapper(adreno_gpu))
> return ret;
> +
> + /* Last step - yield the ringbuffer */
> + a7xx_preempt_start(gpu);
> +
> /*
> * Tell the GMU that we are done touching the GPU and it can start power
> * management
> @@ -1557,8 +1825,13 @@ static irqreturn_t a6xx_irq(struct msm_gpu *gpu)
> if (status & A6XX_RBBM_INT_0_MASK_SWFUSEVIOLATION)
> a7xx_sw_fuse_violation_irq(gpu);
>
> - if (status & A6XX_RBBM_INT_0_MASK_CP_CACHE_FLUSH_TS)
> + if (status & A6XX_RBBM_INT_0_MASK_CP_CACHE_FLUSH_TS) {
> msm_gpu_retire(gpu);
> + a6xx_preempt_trigger(gpu);
> + }
> +
> + if (status & A6XX_RBBM_INT_0_MASK_CP_SW)
> + a6xx_preempt_irq(gpu);
>
> return IRQ_HANDLED;
> }
> @@ -2331,6 +2604,8 @@ struct msm_gpu *a6xx_gpu_init(struct drm_device *dev)
> a6xx_fault_handler);
>
> a6xx_calc_ubwc_config(adreno_gpu);
> + /* Set up the preemption specific bits and pieces for each ringbuffer */
> + a6xx_preempt_init(gpu);
>
> return gpu;
> }
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
> index e3e5c53ae8af..da10060e38dc 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
> @@ -12,6 +12,31 @@
>
> extern bool hang_debug;
>
> +struct cpu_gpu_lock {
> + uint32_t gpu_req;
> + uint32_t cpu_req;
> + uint32_t turn;
> + union {
> + struct {
> + uint16_t list_length;
> + uint16_t list_offset;
> + };
> + struct {
> + uint8_t ifpc_list_len;
> + uint8_t preemption_list_len;
> + uint16_t dynamic_list_len;
> + };
> + };
> + uint64_t regs[62];
> +};
> +
> +struct adreno_reglist_list {
> + /** @reg: List of register **/
> + const u32 *regs;
> + /** @count: Number of registers in the list **/
> + u32 count;
> +};
> +
> /**
> * struct a6xx_info - a6xx specific information from device table
> *
> @@ -31,6 +56,20 @@ struct a6xx_gpu {
> uint64_t sqe_iova;
>
> struct msm_ringbuffer *cur_ring;
> + struct msm_ringbuffer *next_ring;
> +
> + struct drm_gem_object *preempt_bo[MSM_GPU_MAX_RINGS];
> + void *preempt[MSM_GPU_MAX_RINGS];
> + uint64_t preempt_iova[MSM_GPU_MAX_RINGS];
> + uint32_t last_seqno[MSM_GPU_MAX_RINGS];
> +
> + atomic_t preempt_state;
> + spinlock_t eval_lock;
> + struct timer_list preempt_timer;
> +
> + unsigned int preempt_level;
> + bool uses_gmem;
> + bool skip_save_restore;
>
> struct a6xx_gmu gmu;
>
> @@ -38,6 +77,10 @@ struct a6xx_gpu {
> uint64_t shadow_iova;
> uint32_t *shadow;
>
> + struct drm_gem_object *pwrup_reglist_bo;
> + void *pwrup_reglist_ptr;
> + uint64_t pwrup_reglist_iova;
> +
> bool has_whereami;
>
> void __iomem *llc_mmio;
> @@ -49,6 +92,105 @@ struct a6xx_gpu {
>
> #define to_a6xx_gpu(x) container_of(x, struct a6xx_gpu, base)
>
> +/*
> + * In order to do lockless preemption we use a simple state machine to
> progress
> + * through the process.
> + *
> + * PREEMPT_NONE - no preemption in progress. Next state START.
> + * PREEMPT_START - The trigger is evaluating if preemption is possible. Next
> + * states: TRIGGERED, NONE
> + * PREEMPT_FINISH - An intermediate state before moving back to NONE. Next
> + * state: NONE.
> + * PREEMPT_TRIGGERED: A preemption has been executed on the hardware. Next
> + * states: FAULTED, PENDING
> + * PREEMPT_FAULTED: A preemption timed out (never completed). This will
> trigger
> + * recovery. Next state: N/A
> + * PREEMPT_PENDING: Preemption complete interrupt fired - the callback is
> + * checking the success of the operation. Next state: FAULTED, NONE.
> + */
> +
> +enum a6xx_preempt_state {
> + PREEMPT_NONE = 0,
> + PREEMPT_START,
> + PREEMPT_FINISH,
> + PREEMPT_TRIGGERED,
> + PREEMPT_FAULTED,
> + PREEMPT_PENDING,
> +};
> +
> +/*
> + * struct a6xx_preempt_record is a shared buffer between the microcode and
> the
> + * CPU to store the state for preemption. The record itself is much larger
> + * (2112k) but most of that is used by the CP for storage.
> + *
> + * There is a preemption record assigned per ringbuffer. When the CPU
> triggers a
> + * preemption, it fills out the record with the useful information (wptr,
> ring
> + * base, etc) and the microcode uses that information to set up the CP
> following
> + * the preemption. When a ring is switched out, the CP will save the
> ringbuffer
> + * state back to the record. In this way, once the records are properly set
> up
> + * the CPU can quickly switch back and forth between ringbuffers by only
> + * updating a few registers (often only the wptr).
> + *
> + * These are the CPU aware registers in the record:
> + * @magic: Must always be 0xAE399D6EUL
> + * @info: Type of the record - written 0 by the CPU, updated by the CP
> + * @errno: preemption error record
> + * @data: Data field in YIELD and SET_MARKER packets, Written and used by CP
> + * @cntl: Value of RB_CNTL written by CPU, save/restored by CP
> + * @rptr: Value of RB_RPTR written by CPU, save/restored by CP
> + * @wptr: Value of RB_WPTR written by CPU, save/restored by CP
> + * @_pad: Reserved/padding
> + * @rptr_addr: Value of RB_RPTR_ADDR_LO|HI written by CPU, save/restored by
> CP
> + * @rbase: Value of RB_BASE written by CPU, save/restored by CP
> + * @counter: GPU address of the storage area for the preemption counters
doc missing for bv_rptr_addr.
> + */
> +struct a6xx_preempt_record {
> + u32 magic;
> + u32 info;
> + u32 errno;
> + u32 data;
> + u32 cntl;
> + u32 rptr;
> + u32 wptr;
> + u32 _pad;
> + u64 rptr_addr;
> + u64 rbase;
> + u64 counter;
> + u64 bv_rptr_addr;
> +};
> +
> +#define A6XX_PREEMPT_RECORD_MAGIC 0xAE399D6EUL
> +
> +#define PREEMPT_RECORD_SIZE_FALLBACK(size) \
> + ((size) == 0 ? 4192 * SZ_1K : (size))
> +
> +#define PREEMPT_OFFSET_SMMU_INFO 0
> +#define PREEMPT_OFFSET_PRIV_NON_SECURE (PREEMPT_OFFSET_SMMU_INFO + 4096)
> +#define PREEMPT_OFFSET_PRIV_SECURE(size) \
> + (PREEMPT_OFFSET_PRIV_NON_SECURE + PREEMPT_RECORD_SIZE_FALLBACK(size))
> +#define PREEMPT_SIZE(size) \
> + (PREEMPT_OFFSET_PRIV_SECURE(size) + PREEMPT_RECORD_SIZE_FALLBACK(size))
> +
> +/*
> + * The preemption counter block is a storage area for the value of the
> + * preemption counters that are saved immediately before context switch. We
> + * append it on to the end of the allocation for the preemption record.
> + */
> +#define A6XX_PREEMPT_COUNTER_SIZE (16 * 4)
> +
> +#define A6XX_PREEMPT_USER_RECORD_SIZE (192 * 1024)
Unused.
> +
> +struct a7xx_cp_smmu_info {
> + u32 magic;
> + u32 _pad4;
> + u64 ttbr0;
> + u32 asid;
> + u32 context_idr;
> + u32 context_bank;
> +};
> +
> +#define GEN7_CP_SMMU_INFO_MAGIC 0x241350d5UL
> +
> /*
> * Given a register and a count, return a value to program into
> * REG_CP_PROTECT_REG(n) - this will block both reads and writes for
> @@ -106,6 +248,25 @@ int a6xx_gmu_init(struct a6xx_gpu *a6xx_gpu, struct
> device_node *node);
> int a6xx_gmu_wrapper_init(struct a6xx_gpu *a6xx_gpu, struct device_node
> *node);
> void a6xx_gmu_remove(struct a6xx_gpu *a6xx_gpu);
>
> +void a6xx_preempt_init(struct msm_gpu *gpu);
> +void a6xx_preempt_hw_init(struct msm_gpu *gpu);
> +void a6xx_preempt_trigger(struct msm_gpu *gpu);
> +void a6xx_preempt_irq(struct msm_gpu *gpu);
> +void a6xx_preempt_fini(struct msm_gpu *gpu);
> +int a6xx_preempt_submitqueue_setup(struct msm_gpu *gpu,
> + struct msm_gpu_submitqueue *queue);
> +void a6xx_preempt_submitqueue_close(struct msm_gpu *gpu,
> + struct msm_gpu_submitqueue *queue);
> +
> +/* Return true if we are in a preempt state */
> +static inline bool a6xx_in_preempt(struct a6xx_gpu *a6xx_gpu)
> +{
> + int preempt_state = atomic_read(&a6xx_gpu->preempt_state);
I think we should keep a matching barrier before the 'read' similar to the one
used in the
set_preempt_state helper.
> +
> + return !(preempt_state == PREEMPT_NONE ||
> + preempt_state == PREEMPT_FINISH);
> +}
> +
> void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp,
> bool suspended);
> unsigned long a6xx_gmu_get_freq(struct msm_gpu *gpu);
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> new file mode 100644
> index 000000000000..1caff76aca6e
> --- /dev/null
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
> @@ -0,0 +1,391 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2018, The Linux Foundation. All rights reserved. */
> +/* Copyright (c) 2023 Collabora, Ltd. */
> +/* Copyright (c) 2024 Valve Corporation */
> +
> +#include "msm_gem.h"
> +#include "a6xx_gpu.h"
> +#include "a6xx_gmu.xml.h"
> +#include "msm_mmu.h"
> +
> +/*
> + * Try to transition the preemption state from old to new. Return
> + * true on success or false if the original state wasn't 'old'
> + */
> +static inline bool try_preempt_state(struct a6xx_gpu *a6xx_gpu,
> + enum a6xx_preempt_state old, enum a6xx_preempt_state new)
> +{
> + enum a6xx_preempt_state cur = atomic_cmpxchg(&a6xx_gpu->preempt_state,
> + old, new);
> +
> + return (cur == old);
> +}
> +
> +/*
> + * Force the preemption state to the specified state. This is used in cases
> + * where the current state is known and won't change
> + */
> +static inline void set_preempt_state(struct a6xx_gpu *gpu,
> + enum a6xx_preempt_state new)
> +{
> + /*
> + * preempt_state may be read by other cores trying to trigger a
> + * preemption or in the interrupt handler so barriers are needed
> + * before...
> + */
> + smp_mb__before_atomic();
> + atomic_set(&gpu->preempt_state, new);
> + /* ... and after*/
> + smp_mb__after_atomic();
> +}
> +
> +/* Write the most recent wptr for the given ring into the hardware */
> +static inline void update_wptr(struct msm_gpu *gpu, struct msm_ringbuffer
> *ring)
> +{
> + unsigned long flags;
> + uint32_t wptr;
> +
> + if (!ring)
Is this ever true?
> + return;
> +
> + spin_lock_irqsave(&ring->preempt_lock, flags);
> +
> + if (ring->skip_inline_wptr) {
> + wptr = get_wptr(ring);
> +
> + gpu_write(gpu, REG_A6XX_CP_RB_WPTR, wptr);
> +
> + ring->skip_inline_wptr = false;
> + }
> +
> + spin_unlock_irqrestore(&ring->preempt_lock, flags);
> +}
> +
> +/* Return the highest priority ringbuffer with something in it */
> +static struct msm_ringbuffer *get_next_ring(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> +
> + unsigned long flags;
> + int i;
> +
> + for (i = 0; i < gpu->nr_rings; i++) {
> + bool empty;
> + struct msm_ringbuffer *ring = gpu->rb[i];
> +
> + spin_lock_irqsave(&ring->preempt_lock, flags);
> + empty = (get_wptr(ring) == gpu->funcs->get_rptr(gpu, ring));
> + if (!empty && ring == a6xx_gpu->cur_ring)
> + empty = ring->memptrs->fence == a6xx_gpu->last_seqno[i];
> + spin_unlock_irqrestore(&ring->preempt_lock, flags);
> +
> + if (!empty)
> + return ring;
> + }
> +
> + return NULL;
> +}
> +
> +static void a6xx_preempt_timer(struct timer_list *t)
> +{
> + struct a6xx_gpu *a6xx_gpu = from_timer(a6xx_gpu, t, preempt_timer);
> + struct msm_gpu *gpu = &a6xx_gpu->base.base;
> + struct drm_device *dev = gpu->dev;
> +
> + if (!try_preempt_state(a6xx_gpu, PREEMPT_TRIGGERED, PREEMPT_FAULTED))
> + return;
> +
> + dev_err(dev->dev, "%s: preemption timed out\n", gpu->name);
> + kthread_queue_work(gpu->worker, &gpu->recover_work);
> +}
> +
> +void a6xx_preempt_irq(struct msm_gpu *gpu)
> +{
> + uint32_t status;
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + struct drm_device *dev = gpu->dev;
> +
> + if (!try_preempt_state(a6xx_gpu, PREEMPT_TRIGGERED, PREEMPT_PENDING))
> + return;
> +
> + /* Delete the preemption watchdog timer */
> + del_timer(&a6xx_gpu->preempt_timer);
> +
> + /*
> + * The hardware should be setting the stop bit of CP_CONTEXT_SWITCH_CNTL
> + * to zero before firing the interrupt, but there is a non zero chance
> + * of a hardware condition or a software race that could set it again
> + * before we have a chance to finish. If that happens, log and go for
> + * recovery
> + */
> + status = gpu_read(gpu, REG_A6XX_CP_CONTEXT_SWITCH_CNTL);
> + if (unlikely(status & A6XX_CP_CONTEXT_SWITCH_CNTL_STOP)) {
> + DRM_DEV_ERROR(&gpu->pdev->dev,
> + "!!!!!!!!!!!!!!!! preemption faulted
> !!!!!!!!!!!!!! irq\n");
> + set_preempt_state(a6xx_gpu, PREEMPT_FAULTED);
> + dev_err(dev->dev, "%s: Preemption failed to complete\n",
> + gpu->name);
> + kthread_queue_work(gpu->worker, &gpu->recover_work);
> + return;
> + }
> +
> + a6xx_gpu->cur_ring = a6xx_gpu->next_ring;
> + a6xx_gpu->next_ring = NULL;
> +
> + /* Make sure the write to cur_ring is posted before the change in state
> */
> + wmb();
Not needed. set_preempt_state has the necessary barrier.
> +
> + set_preempt_state(a6xx_gpu, PREEMPT_FINISH);
> +
> + update_wptr(gpu, a6xx_gpu->cur_ring);
> +
> + set_preempt_state(a6xx_gpu, PREEMPT_NONE);
> +
> + /*
> + * Retrigger preemption to avoid a deadlock that might occur when
> preemption
> + * is skipped due to it being already in flight when requested.
> + */
> + a6xx_preempt_trigger(gpu);
> +}
> +
> +void a6xx_preempt_hw_init(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + int i;
> +
> + /* No preemption if we only have one ring */
> + if (gpu->nr_rings == 1)
> + return;
> +
> + for (i = 0; i < gpu->nr_rings; i++) {
> + struct a6xx_preempt_record *record_ptr =
> + a6xx_gpu->preempt[i] + PREEMPT_OFFSET_PRIV_NON_SECURE;
> + record_ptr->wptr = 0;
> + record_ptr->rptr = 0;
> + record_ptr->rptr_addr = shadowptr(a6xx_gpu, gpu->rb[i]);
> + record_ptr->info = 0;
> + record_ptr->data = 0;
> + record_ptr->rbase = gpu->rb[i]->iova;
> + }
> +
> + /* Write a 0 to signal that we aren't switching pagetables */
> + gpu_write64(gpu, REG_A6XX_CP_CONTEXT_SWITCH_SMMU_INFO, 0);
> +
> + /* Enable the GMEM save/restore feature for preemption */
> + gpu_write(gpu, REG_A6XX_RB_CONTEXT_SWITCH_GMEM_SAVE_RESTORE, 0x1);
> +
> + /* Reset the preemption state */
> + set_preempt_state(a6xx_gpu, PREEMPT_NONE);
> +
> + spin_lock_init(&a6xx_gpu->eval_lock);
> +
> + /* Always come up on rb 0 */
> + a6xx_gpu->cur_ring = gpu->rb[0];
> +}
> +
> +void a6xx_preempt_trigger(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + u64 preempt_offset_priv_secure;
> + unsigned long flags;
> + struct msm_ringbuffer *ring;
> + unsigned int cntl;
> +
> + if (gpu->nr_rings == 1)
> + return;
> +
> + /*
> + * Lock to make sure another thread attempting preemption doesn't skip
> it
> + * while we are still evaluating the next ring. This makes sure the
> other
> + * thread does start preemption if we abort it and avoids a soft lock.
> + */
> + spin_lock_irqsave(&a6xx_gpu->eval_lock, flags);
> +
> + /*
> + * Try to start preemption by moving from NONE to START. If
> + * unsuccessful, a preemption is already in flight
> + */
> + if (!try_preempt_state(a6xx_gpu, PREEMPT_NONE, PREEMPT_START)) {
> + spin_unlock_irqrestore(&a6xx_gpu->eval_lock, flags);
> + return;
> + }
> +
> + cntl = A6XX_CP_CONTEXT_SWITCH_CNTL_LEVEL(a6xx_gpu->preempt_level);
> +
> + if (a6xx_gpu->skip_save_restore)
> + cntl |= A6XX_CP_CONTEXT_SWITCH_CNTL_SKIP_SAVE_RESTORE;
> +
> + if (a6xx_gpu->uses_gmem)
> + cntl |= A6XX_CP_CONTEXT_SWITCH_CNTL_USES_GMEM;
> +
> + cntl |= A6XX_CP_CONTEXT_SWITCH_CNTL_STOP;
> +
> + /* Get the next ring to preempt to */
> + ring = get_next_ring(gpu);
> +
> + /*
> + * If no ring is populated or the highest priority ring is the current
> + * one do nothing except to update the wptr to the latest and greatest
> + */
> + if (!ring || (a6xx_gpu->cur_ring == ring)) {
> + set_preempt_state(a6xx_gpu, PREEMPT_FINISH);
> + update_wptr(gpu, a6xx_gpu->cur_ring);
> + set_preempt_state(a6xx_gpu, PREEMPT_NONE);
> + spin_unlock_irqrestore(&a6xx_gpu->eval_lock, flags);
> + return;
> + }
> +
> + spin_unlock_irqrestore(&a6xx_gpu->eval_lock, flags);
> +
> + spin_lock_irqsave(&ring->preempt_lock, flags);
> +
> + struct a7xx_cp_smmu_info *smmu_info_ptr =
> + a6xx_gpu->preempt[ring->id] + PREEMPT_OFFSET_SMMU_INFO;
> + struct a6xx_preempt_record *record_ptr =
> + a6xx_gpu->preempt[ring->id] + PREEMPT_OFFSET_PRIV_NON_SECURE;
> + u64 ttbr0 = ring->memptrs->ttbr0;
> + u32 context_idr = ring->memptrs->context_idr;
> +
> + smmu_info_ptr->ttbr0 = ttbr0;
> + smmu_info_ptr->context_idr = context_idr;
> + record_ptr->wptr = get_wptr(ring);
> +
> + /*
> + * The GPU will write the wptr we set above when we preempt. Reset
> + * skip_inline_wptr to make sure that we don't write WPTR to the same
> + * thing twice. It's still possible subsequent submissions will update
> + * wptr again, in which case they will set the flag to true. This has
> + * to be protected by the lock for setting the flag and updating wptr
> + * to be atomic.
> + */
> + ring->skip_inline_wptr = false;
> +
> + spin_unlock_irqrestore(&ring->preempt_lock, flags);
> +
> + gpu_write64(gpu,
> + REG_A6XX_CP_CONTEXT_SWITCH_SMMU_INFO,
> + a6xx_gpu->preempt_iova[ring->id] + PREEMPT_OFFSET_SMMU_INFO);
> +
> + gpu_write64(gpu,
> + REG_A6XX_CP_CONTEXT_SWITCH_PRIV_NON_SECURE_RESTORE_ADDR,
> + a6xx_gpu->preempt_iova[ring->id] +
> PREEMPT_OFFSET_PRIV_NON_SECURE);
> +
> + preempt_offset_priv_secure =
> +
> PREEMPT_OFFSET_PRIV_SECURE(adreno_gpu->info->preempt_record_size);
> + gpu_write64(gpu,
> + REG_A6XX_CP_CONTEXT_SWITCH_PRIV_SECURE_RESTORE_ADDR,
> + a6xx_gpu->preempt_iova[ring->id] + preempt_offset_priv_secure);
Secure buffers are not supported currently, so we can skip this and the
context record allocation. Anyway this has to be a separate buffer
mapped in secure pagetable which don't currently have. We can skip the
same in pseudo register packet too.
> +
> + a6xx_gpu->next_ring = ring;
> +
> + /* Start a timer to catch a stuck preemption */
> + mod_timer(&a6xx_gpu->preempt_timer, jiffies + msecs_to_jiffies(10000));
> +
> + /* Set the preemption state to triggered */
> + set_preempt_state(a6xx_gpu, PREEMPT_TRIGGERED);
> +
> + /* Make sure any previous writes to WPTR are posted */
> + gpu_read(gpu, REG_A6XX_CP_RB_WPTR);
> +
> + /* Make sure everything is written before hitting the button */
> + wmb();
This and the above read back looks unnecessary. All writes to gpu are
ordered anyway.
> +
> + /* Trigger the preemption */
> + gpu_write(gpu, REG_A6XX_CP_CONTEXT_SWITCH_CNTL, cntl);
> +}
> +
> +static int preempt_init_ring(struct a6xx_gpu *a6xx_gpu,
> + struct msm_ringbuffer *ring)
> +{
> + struct adreno_gpu *adreno_gpu = &a6xx_gpu->base;
> + struct msm_gpu *gpu = &adreno_gpu->base;
> + struct drm_gem_object *bo = NULL;
> + phys_addr_t ttbr;
> + u64 iova = 0;
> + void *ptr;
> + int asid;
> +
> + ptr = msm_gem_kernel_new(gpu->dev,
> + PREEMPT_SIZE(adreno_gpu->info->preempt_record_size),
> + MSM_BO_WC | MSM_BO_MAP_PRIV, gpu->aspace, &bo, &iova);
set a name?
> +
> + memset(ptr, 0, PREEMPT_SIZE(adreno_gpu->info->preempt_record_size));
> +
> + if (IS_ERR(ptr))
> + return PTR_ERR(ptr);
> +
> + a6xx_gpu->preempt_bo[ring->id] = bo;
> + a6xx_gpu->preempt_iova[ring->id] = iova;
> + a6xx_gpu->preempt[ring->id] = ptr;
> +
> + struct a7xx_cp_smmu_info *smmu_info_ptr = ptr +
> PREEMPT_OFFSET_SMMU_INFO;
> + struct a6xx_preempt_record *record_ptr = ptr +
> PREEMPT_OFFSET_PRIV_NON_SECURE;
> +
> + msm_iommu_pagetable_params(gpu->aspace->mmu, &ttbr, &asid);
> +
> + smmu_info_ptr->magic = GEN7_CP_SMMU_INFO_MAGIC;
> + smmu_info_ptr->ttbr0 = ttbr;
> + smmu_info_ptr->asid = 0xdecafbad;
> + smmu_info_ptr->context_idr = 0;
> +
> + /* Set up the defaults on the preemption record */
> + record_ptr->magic = A6XX_PREEMPT_RECORD_MAGIC;
> + record_ptr->info = 0;
> + record_ptr->data = 0;
> + record_ptr->rptr = 0;
> + record_ptr->wptr = 0;
> + record_ptr->cntl = MSM_GPU_RB_CNTL_DEFAULT;
> + record_ptr->rbase = ring->iova;
> + record_ptr->counter = 0;
> + record_ptr->bv_rptr_addr = rbmemptr(ring, bv_rptr);
> +
> + return 0;
> +}
> +
> +void a6xx_preempt_fini(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + int i;
> +
> + for (i = 0; i < gpu->nr_rings; i++)
> + msm_gem_kernel_put(a6xx_gpu->preempt_bo[i], gpu->aspace);
> +}
> +
> +void a6xx_preempt_init(struct msm_gpu *gpu)
> +{
> + struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
> + struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
> + int i;
> +
> + /* No preemption if we only have one ring */
> + if (gpu->nr_rings <= 1)
> + return;
> +
> + for (i = 0; i < gpu->nr_rings; i++) {
> + if (preempt_init_ring(a6xx_gpu, gpu->rb[i]))
> + goto fail;
> + }
> +
> + /* TODO: make this configurable? */
> + a6xx_gpu->preempt_level = 1;
> + a6xx_gpu->uses_gmem = 1;
> + a6xx_gpu->skip_save_restore = 1;
> +
> + timer_setup(&a6xx_gpu->preempt_timer, a6xx_preempt_timer, 0);
> +
> + return;
> +fail:
Log an error so that preemption is not disabled silently?
> + /*
> + * On any failure our adventure is over. Clean up and
> + * set nr_rings to 1 to force preemption off
> + */
> + a6xx_preempt_fini(gpu);
> + gpu->nr_rings = 1;
> +
> + return;
> +}
> diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.h
> b/drivers/gpu/drm/msm/msm_ringbuffer.h
> index 40791b2ade46..7dde6a312511 100644
> --- a/drivers/gpu/drm/msm/msm_ringbuffer.h
> +++ b/drivers/gpu/drm/msm/msm_ringbuffer.h
> @@ -36,6 +36,7 @@ struct msm_rbmemptrs {
>
> volatile struct msm_gpu_submit_stats stats[MSM_GPU_SUBMIT_STATS_COUNT];
> volatile u64 ttbr0;
> + volatile u32 context_idr;
> };
>
> struct msm_cp_state {
> @@ -100,6 +101,12 @@ struct msm_ringbuffer {
> * preemption. Can be aquired from irq context.
> */
> spinlock_t preempt_lock;
> +
> + /*
> + * Whether we skipped writing wptr and it needs to be updated in the
> + * future when the ring becomes current.
> + */
> + bool skip_inline_wptr;
nit: does 'restore_wptr' makes more sense? Or something better? Basically,
name it based
on the future action?
-Akhil
> };
>
> struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,
>
> --
> 2.46.0
>
