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

From: Antonino Maniscalco
Date: Mon Sep 09 2024 - 11:08:00 EST

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>