linux-kernel - Re: [PATCH 5/5] drm/amdgpu: resize VRAM BAR for CPU access

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Date:   Mon, 6 Mar 2017 14:06:45 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Christian König <deathsimple@...afone.de>
Cc:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] drm/amdgpu: resize VRAM BAR for CPU access

On Mon, Mar 6, 2017 at 1:40 PM, Christian König <deathsimple@...afone.de> wrote:
> From: Christian König <christian.koenig@....com>
>
> Try to resize BAR0 to let CPU access all of VRAM.

> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -616,6 +616,35 @@ void amdgpu_gtt_location(struct amdgpu_device *adev, struct amdgpu_mc *mc)

> +void amdgpu_resize_bar0(struct amdgpu_device *adev)
> +{
> +       u32 size = max(ilog2(adev->mc.real_vram_size - 1) + 1, 20) - 20;

Too complicated.

unsigned long = fls_long(real_vram_size | BIT(20));

And the result is not a size, right? It's a logarithm from size.

> +       int r;
> +
> +       r = pci_resize_resource(adev->pdev, 0, size);

> +

Redundant line.

> +       if (r == -ENOTSUPP) {
> +               /* The hardware don't support the extension. */
> +               return;
> +
> +       } else if (r == -ENOSPC) {
> +               DRM_INFO("Not enoigh PCI address space for a large BAR.");
> +       } else if (r) {
> +               DRM_ERROR("Problem resizing BAR0 (%d).", r);
> +       }
> +
> +       /* Reinit the doorbell mapping, it is most likely moved as well */
> +       amdgpu_doorbell_fini(adev);

> +       BUG_ON(amdgpu_doorbell_init(adev));

No way to recover?!

> +}
> +

-- 
With Best Regards,
Andy Shevchenko