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

["Lazar, Lijo" <lijo.lazar@amd.com>]

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.Zhao@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);