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 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.

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 Thomas Zimmermann <[email protected]>

Reviewed-by Javier Martinez Canillas <[email protected]>

Reported-by "Ivan T. Ivanov" <[email protected]>

Closes https://bugzilla.suse.com/show_bug.cgi?id=1240696

Tested-by "Ivan T. Ivanov" <[email protected]>

Fixes 78aa89d1dfba ("firmware/sysfb: Update screen_info for relocated EFI framebuffers")

Cc [email protected]

Cc <[email protected]> # v6.9+

---
  drivers/video/screen_info_pci.c | 79 +++++++++++++++++++++------------
  1 file changed, 50 insertions(+), 29 deletions(-)

drivers/video/screen_info_pci.c +50 -29

index 6c5833517141..66bfc1d0a6dc 100644
@@ -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

@@ -47,46 +47,67 @@ 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;
-
-		if (!(r->flags & IORESOURCE_MEM))
-			continue;
-		pr = pci_find_resource(pdev, r);
-		if (!pr)
-			continue;
-
-		/*
-		 * We've found a PCI device with the framebuffer
-		 * resource. Store away the parameters to track
-		 * relocation of the framebuffer aperture.
-		 */
-		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));
-	}
+	/*
+	 * 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);
+
+	pr = pci_find_resource(pdev, &r);
+	if (!pr)
+		return;
+
+	/*
+	 * We've found a PCI device with the framebuffer
+	 * resource. Store away the parameters to track
+	 * relocation of the framebuffer aperture.
+	 */
+	screen_info_lfb_pdev = pdev;
+	screen_info_lfb_bar = pr - pdev->resource;
+	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);