Re: [PATCH] drm/amdgpu: fix clang out-of-range warning

[Christian König]

In general that change looks good. But what configuration is that?

Background is that it doesn't make much sense to compile the amdgpu 
driver on systems where resource_size_t is only 32bit.

Christian.

Am 27.09.21 um 14:19 schrieb Arnd Bergmann:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> clang-14 points out that comparing an 'unsigned int' against a large
> 64-bit constantn is pointless:
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c:1206:18: error: result of comparison of constant 4294967296 with expression of type 'resource_size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>                      res->start > 0x100000000ull)
>
> Rephrase the comparison using the upper_32_bits() macro, which should
> keep it legible while avoiding the warning.
>
> Fixes: 31b8adab3247 ("drm/amdgpu: require a root bus window above 4GB for BAR resize")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index ab3794c42d36..741a55031ca1 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -1203,7 +1203,7 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
>   
>   	pci_bus_for_each_resource(root, res, i) {
>   		if (res && res->flags & (IORESOURCE_MEM | IORESOURCE_MEM_64) &&
> -		    res->start > 0x100000000ull)
> +		    upper_32_bits(res->start) != 0)
>   			break;
>   	}
>