[PATCH 01/43] drm/fbdev-generic: Do not set physical framebuffer address

[Javier Martinez Canillas]

Thomas Zimmermann <tzimmermann at suse.de> writes:

Hello Thomas,

> Framebuffer memory is allocated via vmalloc() from non-contiguous

It's vmalloc() true, but through vzmalloc() so I would mention that
function instead in the commit message.

> physical pages. The physical framebuffer start address is therefore
> meaningless. Do not set it.
>
> The value is not used within the kernel and only exported to userspace
> on dedicated ARM configs. No functional change is expected.
>

How's that info used? Does user-space assumes that the whole memory range
is contiguous in physical memory or just cares about the phyisical start
address ?

> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering")
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Javier Martinez Canillas <javierm at redhat.com>
> Cc: Zack Rusin <zackr at vmware.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>
> Cc: <stable at vger.kernel.org> # v6.4+
> ---
>  drivers/gpu/drm/drm_fbdev_generic.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c
> index d647d89764cb9..b4659cd6285ab 100644
> --- a/drivers/gpu/drm/drm_fbdev_generic.c
> +++ b/drivers/gpu/drm/drm_fbdev_generic.c
> @@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper,
>  	/* screen */
>  	info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST;
>  	info->screen_buffer = screen_buffer;
> -	info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer));
>  	info->fix.smem_len = screen_size;
>  

Makes sense:

Reviewed-by: Javier Martinez Canillas <javierm at redhat.com>

What about drivers/gpu/drm/drm_fb_helper.c btw? Since the memory range
allocated may not be physically contiguous if a platform uses an IOMMU ?

Asking because I don't really know how these exported values are used...
I just know that is when the CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM is enabled.

--
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat