[PATCH v2] video: screen_info: Relocate framebuffers behind PCI bridges

[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. 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.

v2:
- Fixed tags (Takashi, Ivan)
- Updated information on efifb

Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
Reported-by: "Ivan T. Ivanov" <iivanov at suse.de>
Closes: https://bugzilla.suse.com/show_bug.cgi?id=1240696
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,
-- 
2.49.0