Re: [PATCH] drm/amdgpu: Clear VCN cache when hw_init

["Christian König" <christian.koenig@amd.com>]

Am 20.06.23 um 15:29 schrieb Horace Chen:
> [Why]
> VCN will use some framebuffer space as its cache. It needs to
> be reset when reset happens, such as FLR. Otherwise some error
> may be kept after the reset.

Well this doesn't make sense at all.

The full content of adev->vcn.inst[i].cpu_addr is saved and restored 
during suspend/resume and IIRC GPU resets as well.

See functions amdgpu_vcn_suspend() and amdgpu_vcn_resume().

Please let Leo's team take a look at this and review the change before 
it is committed.

Regards,
Christian.

>
> Signed-off-by: Horace Chen <horace.chen@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c
> index b48bb5212488..2db73a964031 100644
> --- a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c
> @@ -1292,6 +1292,7 @@ static int vcn_v4_0_start_sriov(struct amdgpu_device *adev)
>   			cache_size);
>   
>   		cache_addr = adev->vcn.inst[i].gpu_addr + offset;
> +		memset(adev->vcn.inst[i].cpu_addr + offset, 0, AMDGPU_VCN_STACK_SIZE);
>   		MMSCH_V4_0_INSERT_DIRECT_WT(SOC15_REG_OFFSET(VCN, i,
>   			regUVD_LMI_VCPU_CACHE1_64BIT_BAR_LOW),
>   			lower_32_bits(cache_addr));
> @@ -1307,6 +1308,8 @@ static int vcn_v4_0_start_sriov(struct amdgpu_device *adev)
>   
>   		cache_addr = adev->vcn.inst[i].gpu_addr + offset +
>   			AMDGPU_VCN_STACK_SIZE;
> +		memset(adev->vcn.inst[i].cpu_addr + offset + AMDGPU_VCN_STACK_SIZE, 0,
> +			AMDGPU_VCN_STACK_SIZE);
>   		MMSCH_V4_0_INSERT_DIRECT_WT(SOC15_REG_OFFSET(VCN, i,
>   			regUVD_LMI_VCPU_CACHE2_64BIT_BAR_LOW),
>   			lower_32_bits(cache_addr));