[PATCH] video: screen_info: Update framebuffers behind PCI bridges

[Thomas Zimmermann]

cc'ing PCI devs

Am 17.04.25 um 09:27 schrieb Thomas Zimmermann:
> Apply bridge window offsets to screen_info framebuffers during
> relocation. Fixes invalid access to I/O memory.
>
> Resources behind a PCI bridge can be located at a certain offset
> in the kernel's I/O range. The framebuffer memory range stored in
> screen_info refers to the offset as seen during boot (essentialy 0).
> During boot up, the kernel may assign a different memory offset to
> the bridge device and thereby relocating the framebuffer address of
> the PCI graphics device as seen by the kernel. The information in
> screen_info must be updated as well.
>
> The helper pcibios_bus_to_resource() performs the relocation of
> the screen_info resource. The result now matches the I/O-memory
> resource of the PCI graphics device. As before, we store away the
> information necessary to update the information in screen_info.
>
> Commit 78aa89d1dfba ("firmware/sysfb: Update screen_info for relocated
> EFI framebuffers") added the code for updating screen_info. It is
> based on similar functionality that pre-existed in efifb. But efifb
> did not handle bridges correctly, so the problem presumably exists
> only on newer systems.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> Reported-by: Tested-by: "Ivan T. Ivanov" <iivanov at suse.de>
> Closes: https://bugzilla.suse.com/show_bug.cgi?id=1240696
> Tested-by: Tested-by: "Ivan T. Ivanov" <iivanov at suse.de>
> Fixes: 78aa89d1dfba ("firmware/sysfb: Update screen_info for relocated EFI framebuffers")
> Cc: dri-devel at lists.freedesktop.org
> Cc: <stable at vger.kernel.org> # v6.9+
> ---
>   drivers/video/screen_info_pci.c | 17 ++++++++++++++---
>   1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/video/screen_info_pci.c b/drivers/video/screen_info_pci.c
> index 6c5833517141..c46c75dc3fae 100644
> --- a/drivers/video/screen_info_pci.c
> +++ b/drivers/video/screen_info_pci.c
> @@ -8,7 +8,7 @@
>   static struct pci_dev *screen_info_lfb_pdev;
>   static size_t screen_info_lfb_bar;
>   static resource_size_t screen_info_lfb_offset;
> -static struct resource screen_info_lfb_res = DEFINE_RES_MEM(0, 0);
> +static struct pci_bus_region screen_info_lfb_region;
>   
>   static bool __screen_info_relocation_is_valid(const struct screen_info *si, struct resource *pr)
>   {
> @@ -31,7 +31,7 @@ void screen_info_apply_fixups(void)
>   	if (screen_info_lfb_pdev) {
>   		struct resource *pr = &screen_info_lfb_pdev->resource[screen_info_lfb_bar];
>   
> -		if (pr->start != screen_info_lfb_res.start) {
> +		if (pr->start != screen_info_lfb_region.start) {
>   			if (__screen_info_relocation_is_valid(si, pr)) {
>   				/*
>   				 * Only update base if we have an actual
> @@ -69,10 +69,21 @@ static void screen_info_fixup_lfb(struct pci_dev *pdev)
>   
>   	for (i = 0; i < numres; ++i) {
>   		struct resource *r = &res[i];
> +		struct pci_bus_region bus_region = {
> +			.start = r->start,
> +			.end = r->end,
> +		};
>   		const struct resource *pr;
>   
>   		if (!(r->flags & IORESOURCE_MEM))
>   			continue;
> +
> +		/*
> +		 * Translate the address to resource if the framebuffer
> +		 * is behind a PCI bridge.
> +		 */
> +		pcibios_bus_to_resource(pdev->bus, r, &bus_region);
> +
>   		pr = pci_find_resource(pdev, r);
>   		if (!pr)
>   			continue;
> @@ -85,7 +96,7 @@ static void screen_info_fixup_lfb(struct pci_dev *pdev)
>   		screen_info_lfb_pdev = pdev;
>   		screen_info_lfb_bar = pr - pdev->resource;
>   		screen_info_lfb_offset = r->start - pr->start;
> -		memcpy(&screen_info_lfb_res, r, sizeof(screen_info_lfb_res));
> +		memcpy(&screen_info_lfb_region, &bus_region, sizeof(screen_info_lfb_region));
>   	}
>   }
>   DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, 16,

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)