On 9/26/25 01:47, Glenn Miles wrote:
The IBM PPE42 processors support a 32-bit decrementer
that can raise an external interrupt when DEC[0]
transitions from a 0 to a 1 (a non-negative value to a
I guess it was meant to be 0 to -1 (0xffffffff)?
No need to re-spin just for that though.
negative value). It also continues decrementing
even after this condition is met.
The BookE timer is slightly different in that it
raises an interrupt when the DEC value reaches 0
and stops decrementing at that point.
Support a PPE42 version of the BookE timer by
adding a new PPC_TIMER_PPE flag that has the timer
code look for the transition from a non-negative value
to a negative value and allows the value to
continue decrementing.
Signed-off-by: Glenn Miles <[email protected]>
Reviewed-by: Harsh Prateek Bora <[email protected]>
---
hw/ppc/ppc_booke.c | 7 ++++++-
include/hw/ppc/ppc.h | 1 +
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/hw/ppc/ppc_booke.c b/hw/ppc/ppc_booke.c
index 3872ae2822..13403a56b1 100644
--- a/hw/ppc/ppc_booke.c
+++ b/hw/ppc/ppc_booke.c
@@ -352,7 +352,12 @@ void ppc_booke_timers_init(PowerPCCPU *cpu, uint32_t freq,
uint32_t flags)
booke_timer = g_new0(booke_timer_t, 1);
cpu->env.tb_env = tb_env;
- tb_env->flags = flags | PPC_TIMER_BOOKE | PPC_DECR_ZERO_TRIGGERED;
+ if (flags & PPC_TIMER_PPE) {
+ /* PPE's use a modified version of the booke behavior */
+ tb_env->flags = flags | PPC_DECR_UNDERFLOW_TRIGGERED;
+ } else {
+ tb_env->flags = flags | PPC_TIMER_BOOKE | PPC_DECR_ZERO_TRIGGERED;
+ }
tb_env->tb_freq = freq;
tb_env->decr_freq = freq;
diff --git a/include/hw/ppc/ppc.h b/include/hw/ppc/ppc.h
index 8a14d623f8..cb51d704c6 100644
--- a/include/hw/ppc/ppc.h
+++ b/include/hw/ppc/ppc.h
@@ -52,6 +52,7 @@ struct ppc_tb_t {
#define PPC_DECR_UNDERFLOW_LEVEL (1 << 4) /* Decr interrupt active when
* the most significant bit is
1.
*/
+#define PPC_TIMER_PPE (1 << 5) /* Enable PPE support */
uint64_t cpu_ppc_get_tb(ppc_tb_t *tb_env, uint64_t vmclk, int64_t tb_offset);
void cpu_ppc_tb_init(CPUPPCState *env, uint32_t freq);
