Am 29.06.21 um 12:01 schrieb YuBiao Wang:
[Why]
GPU timing counters are read via KIQ under sriov, which will introduce
a delay.
[How]
It could be directly read by MMIO.
v2: Add additional check to prevent carryover issue.
v3: Only check for carryover for once to prevent performance issue.
Signed-off-by: YuBiao Wang <YuBiao.Wang@xxxxxxx>
Acked-by: Horace Chen <horace.chen@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
index ff7e9f49040e..82a5b7ab8dc5 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c
@@ -7610,6 +7610,7 @@ static int gfx_v10_0_soft_reset(void *handle)
static uint64_t gfx_v10_0_get_gpu_clock_counter(struct amdgpu_device *adev)
{
uint64_t clock;
+ uint64_t clock_lo, clock_hi, hi_check;
You could put that on one line.
amdgpu_gfx_off_ctrl(adev, false);
mutex_lock(&adev->gfx.gpu_clock_mutex);
@@ -7620,8 +7621,15 @@ static uint64_t gfx_v10_0_get_gpu_clock_counter(struct amdgpu_device *adev)
((uint64_t)RREG32_SOC15(SMUIO, 0, mmGOLDEN_TSC_COUNT_UPPER_Vangogh) << 32ULL);
break;
default:
- clock = (uint64_t)RREG32_SOC15(SMUIO, 0, mmGOLDEN_TSC_COUNT_LOWER) |
- ((uint64_t)RREG32_SOC15(SMUIO, 0, mmGOLDEN_TSC_COUNT_UPPER) << 32ULL);
+ clock_hi = RREG32_SOC15_NO_KIQ(SMUIO, 0, mmGOLDEN_TSC_COUNT_UPPER);
+ clock_lo = RREG32_SOC15_NO_KIQ(SMUIO, 0, mmGOLDEN_TSC_COUNT_LOWER);
+ hi_check = RREG32_SOC15_NO_KIQ(SMUIO, 0, mmGOLDEN_TSC_COUNT_UPPER);
+ // If carryover happens, update lower count again.
That is obvious and doesn't need a comment, but what you should comment
is how unlikely a carry over is.
E.g. something like carry over only happens every x clock cycles which
are roughly ~y days/weeks/month etc...
And as Monk noted as well please use kernel style comments.
Regards,
Christian.
+ if (hi_check != clock_hi) {
+ clock_lo = RREG32_SOC15_NO_KIQ(SMUIO, 0, mmGOLDEN_TSC_COUNT_LOWER);
+ clock_hi = hi_check;
+ }
+ clock = (uint64_t)clock_lo | ((uint64_t)clock_hi << 32ULL);
break;
}
mutex_unlock(&adev->gfx.gpu_clock_mutex);
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