Re: [PATCH v3 06/10] drm/msm/A6xx: Use posamble to reset counters on preemption

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On 9/6/24 10:08 PM, Akhil P Oommen wrote:
On Thu, Sep 05, 2024 at 04:51:24PM +0200, Antonino Maniscalco wrote:
Use the postamble to reset perf counters when switching between rings,
except when sysprof is enabled, analogously to how they are reset
between submissions when switching pagetables.

Signed-off-by: Antonino Maniscalco <antomani103@xxxxxxxxx>
---
  drivers/gpu/drm/msm/adreno/a6xx_gpu.c     | 20 ++++++++++++++++++-
  drivers/gpu/drm/msm/adreno/a6xx_gpu.h     |  5 +++++
  drivers/gpu/drm/msm/adreno/a6xx_preempt.c | 32 +++++++++++++++++++++++++++++++
  drivers/gpu/drm/msm/adreno/adreno_gpu.h   |  7 +++++--
  4 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index ed0b138a2d66..710ec3ce2923 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -366,7 +366,8 @@ static void a6xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
  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;
+	bool sysprof = refcount_read(&a6xx_gpu->base.base.sysprof_active) > 1;
+	u64 preempt_offset_priv_secure, preempt_postamble;
OUT_PKT7(ring, CP_SET_PSEUDO_REG, 15); @@ -398,6 +399,23 @@ static void a6xx_emit_set_pseudo_reg(struct msm_ringbuffer *ring,
  	/* seems OK to set to 0 to disable it */
  	OUT_RING(ring, 0);
  	OUT_RING(ring, 0);
+
+	/* if not profiling set postamble to clear perfcounters, else clear it */
+	if (!sysprof && a6xx_gpu->preempt_postamble_len) {
+		preempt_postamble = a6xx_gpu->preempt_postamble_iova;
+
+		OUT_PKT7(ring, CP_SET_AMBLE, 3);
+		OUT_RING(ring, lower_32_bits(preempt_postamble));
+		OUT_RING(ring, upper_32_bits(preempt_postamble));
+		OUT_RING(ring, CP_SET_AMBLE_2_DWORDS(
+					a6xx_gpu->preempt_postamble_len) |
+				CP_SET_AMBLE_2_TYPE(KMD_AMBLE_TYPE));
+	} else {

Why do we need this else part?

Wouldn't the postmable remain set if we don't explicitly set it to 0?


+		OUT_PKT7(ring, CP_SET_AMBLE, 3);
+		OUT_RING(ring, 0);
+		OUT_RING(ring, 0);
+		OUT_RING(ring, CP_SET_AMBLE_2_TYPE(KMD_AMBLE_TYPE));
+	}
  }
static void a7xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h b/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
index da10060e38dc..b009732c08c5 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.h
@@ -71,6 +71,11 @@ struct a6xx_gpu {
  	bool uses_gmem;
  	bool skip_save_restore;
+ struct drm_gem_object *preempt_postamble_bo;
+	void *preempt_postamble_ptr;
+	uint64_t preempt_postamble_iova;
+	uint64_t preempt_postamble_len;
+
  	struct a6xx_gmu gmu;
struct drm_gem_object *shadow_bo;
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
index 1caff76aca6e..ec44f44d925f 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_preempt.c
@@ -346,6 +346,28 @@ static int preempt_init_ring(struct a6xx_gpu *a6xx_gpu,
  	return 0;
  }
+static void preempt_prepare_postamble(struct a6xx_gpu *a6xx_gpu)
+{
+	u32 *postamble = a6xx_gpu->preempt_postamble_ptr;
+	u32 count = 0;
+
+	postamble[count++] = PKT7(CP_REG_RMW, 3);
+	postamble[count++] = REG_A6XX_RBBM_PERFCTR_SRAM_INIT_CMD;
+	postamble[count++] = 0;
+	postamble[count++] = 1;
+
+	postamble[count++] = PKT7(CP_WAIT_REG_MEM, 6);
+	postamble[count++] = CP_WAIT_REG_MEM_0_FUNCTION(WRITE_EQ);
+	postamble[count++] = CP_WAIT_REG_MEM_1_POLL_ADDR_LO(
+				REG_A6XX_RBBM_PERFCTR_SRAM_INIT_STATUS);
+	postamble[count++] = CP_WAIT_REG_MEM_2_POLL_ADDR_HI(0);
+	postamble[count++] = CP_WAIT_REG_MEM_3_REF(0x1);
+	postamble[count++] = CP_WAIT_REG_MEM_4_MASK(0x1);
+	postamble[count++] = CP_WAIT_REG_MEM_5_DELAY_LOOP_CYCLES(0);

Isn't it better to just replace this with NOP packets when sysprof is
enabled, just before triggering preemption? It will help to have an
immediate effect.

-Akhil


Mmm, this being a postamble I wonder whether we have the guarantee that it finishes execution before the IRQ is called so updating it doesn't race with the CP executing it.

+
+	a6xx_gpu->preempt_postamble_len = count;
+}
+
  void a6xx_preempt_fini(struct msm_gpu *gpu)
  {
  	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
@@ -376,6 +398,16 @@ void a6xx_preempt_init(struct msm_gpu *gpu)
  	a6xx_gpu->uses_gmem = 1;
  	a6xx_gpu->skip_save_restore = 1;
+ a6xx_gpu->preempt_postamble_ptr = msm_gem_kernel_new(gpu->dev,
+			PAGE_SIZE, MSM_BO_WC | MSM_BO_MAP_PRIV,
+			gpu->aspace, &a6xx_gpu->preempt_postamble_bo,
+			&a6xx_gpu->preempt_postamble_iova);
+
+	preempt_prepare_postamble(a6xx_gpu);
+
+	if (IS_ERR(a6xx_gpu->preempt_postamble_ptr))
+		goto fail;
+
  	timer_setup(&a6xx_gpu->preempt_timer, a6xx_preempt_timer, 0);
return;
diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.h b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
index 6b1888280a83..87098567483b 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.h
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
@@ -610,12 +610,15 @@ OUT_PKT4(struct msm_ringbuffer *ring, uint16_t regindx, uint16_t cnt)
  	OUT_RING(ring, PKT4(regindx, cnt));
  }
+#define PKT7(opcode, cnt) \
+	(CP_TYPE7_PKT | (cnt << 0) | (PM4_PARITY(cnt) << 15) | \
+		((opcode & 0x7F) << 16) | (PM4_PARITY(opcode) << 23))
+
  static inline void
  OUT_PKT7(struct msm_ringbuffer *ring, uint8_t opcode, uint16_t cnt)
  {
  	adreno_wait_ring(ring, cnt + 1);
-	OUT_RING(ring, CP_TYPE7_PKT | (cnt << 0) | (PM4_PARITY(cnt) << 15) |
-		((opcode & 0x7F) << 16) | (PM4_PARITY(opcode) << 23));
+	OUT_RING(ring, PKT7(opcode, cnt));
  }
struct msm_gpu *a2xx_gpu_init(struct drm_device *dev);

--
2.46.0


Best regards,
--
Antonino Maniscalco <antomani103@xxxxxxxxx>





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