firmware/sysfb: Update screen_info for relocated EFI framebuffers

On ARM PCI systems, the PCI hierarchy might be reconfigured during
boot and the firmware framebuffer might move as a result of that.
The values in screen_info will then be invalid.

Work around this problem by tracking the framebuffer's initial
location before it get relocated; then fix the screen_info state
between reloaction and creating the firmware framebuffer's device.

This functionality has been lifted from efifb. See the commit message
of commit 55d728a40d36 ("efi/fb: Avoid reconfiguration of BAR that
covers the framebuffer") for more information.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240212090736.11464-8-tzimmermann@suse.de

1 files changed, 88 insertions, 0 deletions

diff --git a/drivers/video/screen_info_pci.c b/drivers/video/screen_info_pci.c
index d8985a54ce71..6c5833517141 100644
--- a/drivers/video/screen_info_pci.c
+++ b/drivers/video/screen_info_pci.c
@@ -1,7 +1,95 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/pci.h>
+#include <linux/printk.h>
 #include <linux/screen_info.h>
+#include <linux/string.h>
+
+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 bool __screen_info_relocation_is_valid(const struct screen_info *si, struct resource *pr)
+{
+	u64 size = __screen_info_lfb_size(si, screen_info_video_type(si));
+
+	if (screen_info_lfb_offset > resource_size(pr))
+		return false;
+	if (size > resource_size(pr))
+		return false;
+	if (resource_size(pr) - size < screen_info_lfb_offset)
+		return false;
+
+	return true;
+}
+
+void screen_info_apply_fixups(void)
+{
+	struct screen_info *si = &screen_info;
+
+	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 (__screen_info_relocation_is_valid(si, pr)) {
+				/*
+				 * Only update base if we have an actual
+				 * relocation to a valid I/O range.
+				 */
+				__screen_info_set_lfb_base(si, pr->start + screen_info_lfb_offset);
+				pr_info("Relocating firmware framebuffer to offset %pa[d] within %pr\n",
+					&screen_info_lfb_offset, pr);
+			} else {
+				pr_warn("Invalid relocating, disabling firmware framebuffer\n");
+			}
+		}
+	}
+}
+
+static void screen_info_fixup_lfb(struct pci_dev *pdev)
+{
+	unsigned int type;
+	struct resource res[SCREEN_INFO_MAX_RESOURCES];
+	size_t i, numres;
+	int ret;
+	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
+
+	ret = screen_info_resources(si, res, ARRAY_SIZE(res));
+	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));
+	}
+}
+DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, 16,
+			       screen_info_fixup_lfb);
 
 static struct pci_dev *__screen_info_pci_dev(struct resource *res)
 {