Re: [PATCH v2 2/2] drm/amdgpu: Read RLC GPU clock on GFX12.1 VF

[Lazar, Lijo]

On 24-Sep-26 12:05 PM, Victor Zhao wrote:
[why]
VF timestamp queries need a TSC sample independent of CP/MES.
The SMUIO path is not safe on VF.

[how]
Capture via RLC_CAPTURE_GPU_CLOCK_COUNT and read the consecutive
count registers with amdgpu_mes_rreg64().

Signed-off-by: Victor Zhao <victor.z...@amd.com>
---
  drivers/gpu/drm/amd/amdgpu/gfx_v12_1.c | 26 ++++++++++++++++++++++++++
  1 file changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v12_1.c 
b/drivers/gpu/drm/amd/amdgpu/gfx_v12_1.c
index d6f70d33201a0..3c8133c94d6fc 100644
--- a/drivers/gpu/drm/amd/amdgpu/gfx_v12_1.c
+++ b/drivers/gpu/drm/amd/amdgpu/gfx_v12_1.c
@@ -3168,10 +3168,36 @@ static int gfx_v12_1_wait_for_idle(struct 
amdgpu_ip_block *ip_block)
        return -ETIMEDOUT;
  }
  
+static uint64_t gfx_v12_1_get_rlc_gpu_clock_counter(struct amdgpu_device *adev)
+{
+       uint64_t clock = 0;
+       uint32_t reg;
+
+       if (!down_read_trylock(&adev->reset_domain->sem))
+               return 0;
+       if (amdgpu_device_skip_hw_access(adev) ||
+           !adev->mes.ring[0].sched.ready)
+               goto unlock_reset;
+
+       mutex_lock(&adev->gfx.gpu_clock_mutex);
+       WREG32_SOC15(GC, GET_INST(GC, 0), regRLC_CAPTURE_GPU_CLOCK_COUNT, 1);
+       reg = SOC15_REG_OFFSET(GC, GET_INST(GC, 0),
+                              regRLC_GPU_CLOCK_COUNT_LSB);
+       clock = amdgpu_mes_rreg64(adev, reg, 0);

The API error cases should be checked and the clock value (0?) should be 
returned accordingly to indicate an invalid counter value.

Thanks,
Lijo
+       mutex_unlock(&adev->gfx.gpu_clock_mutex);
+
+unlock_reset:
+       up_read(&adev->reset_domain->sem);
+       return clock;
+}
+
  static uint64_t gfx_v12_1_get_gpu_clock_counter(struct amdgpu_device *adev)
  {
        uint64_t clock = 0;
  
+	if (amdgpu_sriov_vf(adev))
+               return gfx_v12_1_get_rlc_gpu_clock_counter(adev);
+
        if (adev->smuio.funcs &&
            adev->smuio.funcs->get_gpu_clock_counter)
                clock = adev->smuio.funcs->get_gpu_clock_counter(adev);