Commit 2f29b5c2 authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

video: screen_info: Relocate framebuffers behind PCI bridges 



Apply PCI host-bridge window offsets to screen_info framebuffers. Fixes
invalid access to I/O memory.

Resources behind a PCI host bridge can be relocated by a certain offset
in the kernel's CPU address range used for I/O. The framebuffer memory
range stored in screen_info refers to the CPU addresses as seen during
boot (where the offset is 0). During boot up, firmware may assign a
different memory offset to the PCI host bridge 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's framebuffer resource (given in PCI bus addresses). The
result matches the I/O-memory resource of the PCI graphics device (given
in CPU addresses). As before, we store away the information necessary to
later update the information in screen_info itself.

Commit 78aa89d1 ("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. Efifb uses a pointer
to the PCI resource, while the newer code does a memcpy of the region.
Hence efifb sees any updates to the PCI resource and avoids the issue.

v3:
- Only use struct pci_bus_region for PCI bus addresses (Bjorn)
- Clarify address semantics in commit messages and comments (Bjorn)
v2:
- Fixed tags (Takashi, Ivan)
- Updated information on efifb

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Reported-by: default avatar"Ivan T. Ivanov" <iivanov@suse.de>
Closes: https://bugzilla.suse.com/show_bug.cgi?id=1240696


Tested-by: default avatar"Ivan T. Ivanov" <iivanov@suse.de>
Fixes: 78aa89d1 ("firmware/sysfb: Update screen_info for relocated EFI framebuffers")
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.9+
Link: https://lore.kernel.org/r/20250528080234.7380-1-tzimmermann@suse.de
parent 91274fd4

drivers/video/screen_info_pci.c

+50 −29
Original line number Diff line number Diff line
@@ -7,8 +7,8 @@ 


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 resource_size_t screen_info_lfb_res_start; // original start of resource

static resource_size_t screen_info_lfb_offset; // framebuffer offset within resource



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_res_start) {

			if (__screen_info_relocation_is_valid(si, pr)) {

				/*

				 * Only update base if we have an actual
@@ -47,35 +47,57 @@ void screen_info_apply_fixups(void) 
	}

}



static int __screen_info_lfb_pci_bus_region(const struct screen_info *si, unsigned int type,

					    struct pci_bus_region *r)

{

	u64 base, size;



	base = __screen_info_lfb_base(si);

	if (!base)

		return -EINVAL;



	size = __screen_info_lfb_size(si, type);

	if (!size)

		return -EINVAL;



	r->start = base;

	r->end = base + size - 1;



	return 0;

}



static void screen_info_fixup_lfb(struct pci_dev *pdev)

{

	unsigned int type;

	struct resource res[SCREEN_INFO_MAX_RESOURCES];

	size_t i, numres;

	struct pci_bus_region bus_region;

	int ret;

	struct resource r = {

		.flags = IORESOURCE_MEM,

	};

	const struct resource *pr;

	const struct screen_info *si = &screen_info;



	if (screen_info_lfb_pdev)

		return; // already found



	type = screen_info_video_type(si);

	if (type != VIDEO_TYPE_EFI)

		return; // only applies to EFI

	if (!__screen_info_has_lfb(type))

		return; // only applies to EFI; maybe VESA



	ret = screen_info_resources(si, res, ARRAY_SIZE(res));

	ret = __screen_info_lfb_pci_bus_region(si, type, &bus_region);

	if (ret < 0)

		return;

	numres = ret;



	for (i = 0; i < numres; ++i) {

		struct resource *r = &res[i];

		const struct resource *pr;

	/*

	 * Translate the PCI bus address to resource. Account

	 * for an offset if the framebuffer is behind a PCI host

	 * bridge.

	 */

	pcibios_bus_to_resource(pdev->bus, &r, &bus_region);



		if (!(r->flags & IORESOURCE_MEM))

			continue;

		pr = pci_find_resource(pdev, r);

	pr = pci_find_resource(pdev, &r);

	if (!pr)

			continue;

		return;



	/*

	 * We've found a PCI device with the framebuffer
@@ -84,9 +106,8 @@ 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));

	}

	screen_info_lfb_offset = r.start - pr->start;

	screen_info_lfb_res_start = bus_region.start;

}

DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, 16,

			       screen_info_fixup_lfb);