Commit 78aa89d1 authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

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 55d728a4 ("efi/fb: Avoid reconfiguration of BAR that
covers the framebuffer") for more information.

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240212090736.11464-8-tzimmermann@suse.de
parent 784e27f2

drivers/firmware/sysfb.c

+2 −0
Original line number Diff line number Diff line
@@ -118,6 +118,8 @@ static __init int sysfb_init(void) 
	bool compatible;

	int ret = 0;



	screen_info_apply_fixups();



	mutex_lock(&disable_lock);

	if (disabled)

		goto unlock_mutex;

drivers/video/screen_info_pci.c

+88 −0
Original line number Diff line number Diff line 
// 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)

{

include/linux/screen_info.h

+16 −0
Original line number Diff line number Diff line
@@ -4,6 +4,8 @@ 


#include <uapi/linux/screen_info.h>



#include <linux/bits.h>



/**

 * SCREEN_INFO_MAX_RESOURCES - maximum number of resources per screen_info

 */
@@ -27,6 +29,17 @@ static inline u64 __screen_info_lfb_base(const struct screen_info *si) 
	return lfb_base;

}



static inline void __screen_info_set_lfb_base(struct screen_info *si, u64 lfb_base)

{

	si->lfb_base = lfb_base & GENMASK_ULL(31, 0);

	si->ext_lfb_base = (lfb_base & GENMASK_ULL(63, 32)) >> 32;



	if (si->ext_lfb_base)

		si->capabilities |= VIDEO_CAPABILITY_64BIT_BASE;

	else

		si->capabilities &= ~VIDEO_CAPABILITY_64BIT_BASE;

}



static inline u64 __screen_info_lfb_size(const struct screen_info *si, unsigned int type)

{

	u64 lfb_size = si->lfb_size;
@@ -106,8 +119,11 @@ static inline unsigned int screen_info_video_type(const struct screen_info *si) 
ssize_t screen_info_resources(const struct screen_info *si, struct resource *r, size_t num);



#if defined(CONFIG_PCI)

void screen_info_apply_fixups(void);

struct pci_dev *screen_info_pci_dev(const struct screen_info *si);

#else

static inline void screen_info_apply_fixups(void)

{ }

static inline struct pci_dev *screen_info_pci_dev(const struct screen_info *si)

{

	return NULL;