Re: [PATCH v2] drm/amdgpu: Check extended configuration space register when system uses large bar

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

Am 09.01.24 um 11:31 schrieb Ma Jun:
> Some customer platforms do not enable mmconfig for various reasons,
> such as bios bug, and therefore cannot access the GPU extend configuration
> space through mmio.
>
> When the system enters the d3cold state and resumes, the amdgpu driver
> fails to resume because the extend configuration space registers of
> GPU can't be restored. At this point, Usually we only see some failure
> dmesg log printed by amdgpu driver, it is difficult to find the root
> cause.
>
> Therefor print a warnning message if the system can't access the
> extended configuration space register when using large bar.
>
> Signed-off-by: Ma Jun <Jun.Ma2@amd.com>
> ---
> v2:
> - Check the register at 0x100 but not resize bar register(Christian)
> - Modify the commit message
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 4b694696930e..0d7d55f13b8b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -1417,6 +1417,13 @@ void amdgpu_device_wb_free(struct amdgpu_device *adev, u32 wb)
>   		__clear_bit(wb, adev->wb.used);
>   }
>   
> +static inline void amdgpu_device_check_extended_capability(struct amdgpu_device *adev)

Please don't use inline when it's not necessary, see the coding style 
guide as well.

> +{
> +	/* PCI_EXT_CAP_ID_VNDR extended capability is located at 0x100 */
> +	if (!pci_find_ext_capability(adev->pdev, PCI_EXT_CAP_ID_VNDR))
> +		DRM_WARN("System can't access extended configuration space,please check!!\n");
> +}
> +
>   /**
>    * amdgpu_device_resize_fb_bar - try to resize FB BAR
>    *
> @@ -1444,8 +1451,10 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
>   
>   	/* skip if the bios has already enabled large BAR */
>   	if (adev->gmc.real_vram_size &&
> -	    (pci_resource_len(adev->pdev, 0) >= adev->gmc.real_vram_size))
> +	    (pci_resource_len(adev->pdev, 0) >= adev->gmc.real_vram_size)) {
> +		amdgpu_device_check_extended_capability(adev);

We should probably check this case independent of the BAR size since we 
will most likely run into trouble with error reporting as well.

Christian.

>   		return 0;
> +	}
>   
>   	/* Check if the root BUS has 64bit memory resources */
>   	root = adev->pdev->bus;