Upon enabling histogram an interrupt is trigerred after the generation
of the statistics. This patch registers the histogram interrupt and
handles the interrupt.

v2: Added intel_crtc backpointer to intel_histogram struct (Jani)
    Removed histogram_wq and instead use dev_priv->unodered_eq (Jani)
v3: Replaced drm_i915_private with intel_display (Suraj)
    Refactored the histogram read code (Jani)
v4: Rebased after addressing comments on patch 1

Signed-off-by: Arun R Murthy <arun.r.mur...@intel.com>
---
 .../gpu/drm/i915/display/intel_display_irq.c  |  6 +-
 .../gpu/drm/i915/display/intel_histogram.c    | 93 +++++++++++++++++++
 .../gpu/drm/i915/display/intel_histogram.h    |  3 +
 drivers/gpu/drm/i915/i915_reg.h               |  5 +-
 4 files changed, 104 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_irq.c 
b/drivers/gpu/drm/i915/display/intel_display_irq.c
index 6878dde85031..40514966a2ea 100644
--- a/drivers/gpu/drm/i915/display/intel_display_irq.c
+++ b/drivers/gpu/drm/i915/display/intel_display_irq.c
@@ -20,6 +20,7 @@
 #include "intel_fdi_regs.h"
 #include "intel_fifo_underrun.h"
 #include "intel_gmbus.h"
+#include "intel_histogram.h"
 #include "intel_hotplug_irq.h"
 #include "intel_pipe_crc_regs.h"
 #include "intel_pmdemand.h"
@@ -1190,6 +1191,9 @@ void gen8_de_irq_handler(struct drm_i915_private 
*dev_priv, u32 master_ctl)
                if (iir & gen8_de_pipe_underrun_mask(dev_priv))
                        intel_cpu_fifo_underrun_irq_handler(dev_priv, pipe);
 
+               if (iir & GEN9_PIPE_HISTOGRAM_EVENT)
+                       intel_histogram_irq_handler(display, pipe);
+
                fault_errors = iir & gen8_de_pipe_fault_mask(dev_priv);
                if (fault_errors)
                        drm_err_ratelimited(&dev_priv->drm,
@@ -1756,7 +1760,7 @@ void gen8_de_irq_postinstall(struct drm_i915_private 
*dev_priv)
        struct intel_uncore *uncore = &dev_priv->uncore;
 
        u32 de_pipe_masked = gen8_de_pipe_fault_mask(dev_priv) |
-               GEN8_PIPE_CDCLK_CRC_DONE;
+               GEN8_PIPE_CDCLK_CRC_DONE | GEN9_PIPE_HISTOGRAM_EVENT;
        u32 de_pipe_enables;
        u32 de_port_masked = gen8_de_port_aux_mask(dev_priv);
        u32 de_port_enables;
diff --git a/drivers/gpu/drm/i915/display/intel_histogram.c 
b/drivers/gpu/drm/i915/display/intel_histogram.c
index 86439636b490..ce2a5eae2784 100644
--- a/drivers/gpu/drm/i915/display/intel_histogram.c
+++ b/drivers/gpu/drm/i915/display/intel_histogram.c
@@ -18,6 +18,8 @@
 #define HISTOGRAM_GUARDBAND_THRESHOLD_DEFAULT 300    // 3.0% of the pipe's 
current pixel count.
 #define HISTOGRAM_GUARDBAND_PRECISION_FACTOR 10000   // Precision factor for 
threshold guardband.
 #define HISTOGRAM_DEFAULT_GUARDBAND_DELAY 0x04
+#define HISTOGRAM_BIN_READ_RETRY_COUNT 5
+#define HISTOGRAM_BIN_READ_DELAY 2
 
 struct intel_histogram {
        struct intel_crtc *crtc;
@@ -27,6 +29,92 @@ struct intel_histogram {
        u32 bin_data[HISTOGRAM_BIN_COUNT];
 };
 
+static bool intel_histogram_get_data(struct intel_crtc *intel_crtc)
+{
+       struct intel_display *display = to_intel_display(intel_crtc);
+       struct intel_histogram *histogram = intel_crtc->histogram;
+       u8 index, retry_count;
+       u32 dpstbin;
+
+       index = 0;
+       retry_count = 0;
+
+       while (index < HISTOGRAM_BIN_COUNT) {
+               dpstbin = intel_de_read(display, DPST_BIN(intel_crtc->pipe));
+               if (!(dpstbin & DPST_BIN_BUSY)) {
+                       histogram->bin_data[index] = dpstbin & 
DPST_BIN_DATA_MASK;
+                       index++;
+               } else {
+                       /*
+                        * If DPST_BIN busy bit is set, then set the
+                        * DPST_CTL bin reg index to 0 and proceed
+                        * from beginning.
+                        */
+                       retry_count++;
+                       if (retry_count > HISTOGRAM_BIN_READ_RETRY_COUNT) {
+                               drm_err(display->drm, "Histogram bin read 
failed with max retry\n");
+                               return false;
+                       }
+                       /* Add a delay before retrying */
+                       fsleep(HISTOGRAM_BIN_READ_DELAY);
+                       index = 0;
+                       intel_de_rmw(display, DPST_CTL(intel_crtc->pipe),
+                                    DPST_CTL_BIN_REG_FUNC_SEL |
+                                    DPST_CTL_BIN_REG_MASK, 0);
+               }
+       }
+       return true;
+}
+
+static void intel_histogram_handle_int_work(struct work_struct *work)
+{
+       struct intel_histogram *histogram = container_of(work,
+               struct intel_histogram, work.work);
+       struct intel_crtc *intel_crtc = histogram->crtc;
+       struct intel_display *display = to_intel_display(intel_crtc);
+       char *histogram_event[] = {"HISTOGRAM=1", NULL};
+
+       /*
+        * TODO: PSR to be exited while reading the Histogram data
+        * Set DPST_CTL Bin Reg function select to TC
+        * Set DPST_CTL Bin Register Index to 0
+        */
+       intel_de_rmw(display, DPST_CTL(intel_crtc->pipe),
+                    DPST_CTL_BIN_REG_FUNC_SEL | DPST_CTL_BIN_REG_MASK, 0);
+       if (intel_histogram_get_data(intel_crtc)) {
+               /* Notify user for Histogram rediness */
+               if (kobject_uevent_env(&display->drm->primary->kdev->kobj,
+                                      KOBJ_CHANGE, histogram_event))
+                       drm_err(display->drm,
+                               "sending HISTOGRAM event failed\n");
+       }
+
+       /* Enable histogram interrupt */
+       intel_de_rmw(display, DPST_GUARD(intel_crtc->pipe), 
DPST_GUARD_HIST_INT_EN,
+                    DPST_GUARD_HIST_INT_EN);
+
+       /* Clear histogram interrupt by setting histogram interrupt status bit*/
+       intel_de_rmw(display, DPST_GUARD(intel_crtc->pipe),
+                    DPST_GUARD_HIST_EVENT_STATUS, 1);
+}
+
+void intel_histogram_irq_handler(struct intel_display *display, enum pipe pipe)
+{
+       struct intel_crtc *intel_crtc =
+               to_intel_crtc(drm_crtc_from_index(display->drm, pipe));
+       struct intel_histogram *histogram = intel_crtc->histogram;
+       struct drm_i915_private *i915 = to_i915(intel_crtc->base.dev);
+
+       if (!histogram->enable) {
+               drm_err(display->drm,
+                       "spurious interrupt, histogram not enabled\n");
+               return;
+       }
+
+       queue_delayed_work(i915->unordered_wq,
+                          &histogram->work, 0);
+}
+
 int intel_histogram_atomic_check(struct intel_crtc *intel_crtc)
 {
        struct intel_histogram *histogram = intel_crtc->histogram;
@@ -105,6 +193,7 @@ static void intel_histogram_disable(struct intel_crtc 
*intel_crtc)
        intel_de_rmw(display, DPST_CTL(pipe),
                     DPST_CTL_IE_HIST_EN, 0);
 
+       cancel_delayed_work(&histogram->work);
        histogram->enable = false;
 }
 
@@ -166,6 +255,7 @@ void intel_histogram_finish(struct intel_crtc *intel_crtc)
 {
        struct intel_histogram *histogram = intel_crtc->histogram;
 
+       cancel_delayed_work_sync(&histogram->work);
        kfree(histogram);
 }
 
@@ -183,5 +273,8 @@ int intel_histogram_init(struct intel_crtc *intel_crtc)
        histogram->crtc = intel_crtc;
        histogram->can_enable = false;
 
+       INIT_DEFERRABLE_WORK(&histogram->work,
+                            intel_histogram_handle_int_work);
+
        return 0;
 }
diff --git a/drivers/gpu/drm/i915/display/intel_histogram.h 
b/drivers/gpu/drm/i915/display/intel_histogram.h
index 9d66724f9c53..14f2425e3038 100644
--- a/drivers/gpu/drm/i915/display/intel_histogram.h
+++ b/drivers/gpu/drm/i915/display/intel_histogram.h
@@ -9,6 +9,8 @@
 #include <linux/types.h>
 
 struct intel_crtc;
+struct intel_display;
+enum pipe;
 
 #define HISTOGRAM_BIN_COUNT                    32
 #define HISTOGRAM_IET_LENGTH                   33
@@ -27,6 +29,7 @@ enum intel_global_hist_lut {
 };
 
 int intel_histogram_atomic_check(struct intel_crtc *intel_crtc);
+void intel_histogram_irq_handler(struct intel_display *display, enum pipe 
pipe);
 int intel_histogram_update(struct intel_crtc *intel_crtc, bool enable);
 int intel_histogram_set_iet_lut(struct intel_crtc *intel_crtc, u32 *data);
 int intel_histogram_init(struct intel_crtc *intel_crtc);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 7396fc630e29..7e062d6c8901 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1643,7 +1643,7 @@
 #define   PIPE_HOTPLUG_INTERRUPT_ENABLE                (1UL << 26)
 #define   PIPE_VSYNC_INTERRUPT_ENABLE          (1UL << 25)
 #define   PIPE_DISPLAY_LINE_COMPARE_ENABLE     (1UL << 24)
-#define   PIPE_DPST_EVENT_ENABLE               (1UL << 23)
+#define   PIPE_HISTOGRAM_EVENT_ENABLE          (1UL << 23)
 #define   SPRITE0_FLIP_DONE_INT_EN_VLV         (1UL << 22)
 #define   PIPE_LEGACY_BLC_EVENT_ENABLE         (1UL << 22)
 #define   PIPE_ODD_FIELD_INTERRUPT_ENABLE      (1UL << 21)
@@ -1666,7 +1666,7 @@
 #define   PIPE_HOTPLUG_INTERRUPT_STATUS                (1UL << 10)
 #define   PIPE_VSYNC_INTERRUPT_STATUS          (1UL << 9)
 #define   PIPE_DISPLAY_LINE_COMPARE_STATUS     (1UL << 8)
-#define   PIPE_DPST_EVENT_STATUS               (1UL << 7)
+#define   PIPE_HISTOGRAM_EVENT_STATUS          (1UL << 7)
 #define   PIPE_A_PSR_STATUS_VLV                        (1UL << 6)
 #define   PIPE_LEGACY_BLC_EVENT_STATUS         (1UL << 6)
 #define   PIPE_ODD_FIELD_INTERRUPT_STATUS      (1UL << 5)
@@ -2505,6 +2505,7 @@
 #define  GEN12_DSB_1_INT               REG_BIT(14) /* tgl+ */
 #define  GEN12_DSB_0_INT               REG_BIT(13) /* tgl+ */
 #define  GEN12_DSB_INT(dsb_id)         REG_BIT(13 + (dsb_id))
+#define  GEN9_PIPE_HISTOGRAM_EVENT     REG_BIT(12) /* skl+ */
 #define  GEN9_PIPE_CURSOR_FAULT                REG_BIT(11) /* skl+ */
 #define  GEN9_PIPE_PLANE4_FAULT                REG_BIT(10) /* skl+ */
 #define  GEN8_PIPE_CURSOR_FAULT                REG_BIT(10) /* bdw */
-- 
2.25.1

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