Re: [PATCH] fbdev: efifb: do not load efifb if PCI BAR has changed but not fixuped

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 26.06.25 um 11:49 schrieb oushixiong1025@163.com:
> From: Shixiong Ou <oushixiong@kylinos.cn>
>
> [WHY]
> On an ARM machine, the following log is present:
> [    0.900884] efifb: framebuffer at 0x1020000000, using 3072k, total 3072k
> [    2.297884] amdgpu 0000:04:00.0: remove_conflicting_pci_framebuffers: bar 0: 0x1000000000 -> 0x100fffffff
> [    2.297886] amdgpu 0000:04:00.0: remove_conflicting_pci_framebuffers: bar 2: 0x1010000000 -> 0x10101fffff
> [    2.297888] amdgpu 0000:04:00.0: remove_conflicting_pci_framebuffers: bar 5: 0x58200000 -> 0x5823ffff
>
> It show that the efifb framebuffer base is out of PCI BAR, and this

The patch at

   https://patchwork.freedesktop.org/series/148057/

is supposed to fix the problem. It has been merged with v6.16-rc1 as 
commit 2f29b5c23101 ("video: screen_info: Relocate framebuffers behind 
PCI bridges"). It is in your tree?

Best regards
Thomas

> results in both efi-framebuffer and amdgpudrmfb co-existing.
>
> The fbcon will be bound to efi-framebuffer by default and cannot be used.
>
> [HOW]
> Do not load efifb driver if PCI BAR has changed but not fixuped.
> In the following cases:
> 	1. screen_info_lfb_pdev is NULL.
> 	2. __screen_info_relocation_is_valid return false.
>
> Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
> ---
>   drivers/video/fbdev/efifb.c     |  4 ++++
>   drivers/video/screen_info_pci.c | 24 ++++++++++++++++++++++++
>   include/linux/screen_info.h     |  5 +++++
>   3 files changed, 33 insertions(+)
>
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index 0e1bd3dba255..de8d016c9a66 100644
> --- a/drivers/video/fbdev/efifb.c
> +++ b/drivers/video/fbdev/efifb.c
> @@ -303,6 +303,10 @@ static void efifb_setup(struct screen_info *si, char *options)
>   
>   static inline bool fb_base_is_valid(struct screen_info *si)
>   {
> +	/* check whether fb_base has changed but not fixuped */
> +	if (!screen_info_is_useful())
> +		return false;
> +
>   	if (si->lfb_base)
>   		return true;
>   
> diff --git a/drivers/video/screen_info_pci.c b/drivers/video/screen_info_pci.c
> index 66bfc1d0a6dc..ac57dcaf0cac 100644
> --- a/drivers/video/screen_info_pci.c
> +++ b/drivers/video/screen_info_pci.c
> @@ -9,6 +9,8 @@ static struct pci_dev *screen_info_lfb_pdev;
>   static size_t screen_info_lfb_bar;
>   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_changed;
> +static bool screen_info_fixuped;
>   
>   static bool __screen_info_relocation_is_valid(const struct screen_info *si, struct resource *pr)
>   {
> @@ -24,6 +26,24 @@ static bool __screen_info_relocation_is_valid(const struct screen_info *si, stru
>   	return true;
>   }
>   
> +bool screen_info_is_useful(void)
> +{
> +	unsigned int type;
> +	const struct screen_info *si = &screen_info;
> +
> +	type = screen_info_video_type(si);
> +	if (type != VIDEO_TYPE_EFI)
> +		return true;
> +
> +	if (screen_info_changed && !screen_info_fixuped) {
> +		pr_warn("The screen_info has changed but not fixuped");
> +		return false;
> +	}
> +
> +	pr_info("The screen_info is useful");
> +	return true;
> +}
> +
>   void screen_info_apply_fixups(void)
>   {
>   	struct screen_info *si = &screen_info;
> @@ -32,18 +52,22 @@ void screen_info_apply_fixups(void)
>   		struct resource *pr = &screen_info_lfb_pdev->resource[screen_info_lfb_bar];
>   
>   		if (pr->start != screen_info_lfb_res_start) {
> +			screen_info_changed = true;
>   			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);
> +				screen_info_fixuped = true;
>   				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");
>   			}
>   		}
> +	} else {
> +		screen_info_changed = true;
>   	}
>   }
>   
> diff --git a/include/linux/screen_info.h b/include/linux/screen_info.h
> index 923d68e07679..632cdbb1adbe 100644
> --- a/include/linux/screen_info.h
> +++ b/include/linux/screen_info.h
> @@ -138,9 +138,14 @@ ssize_t screen_info_resources(const struct screen_info *si, struct resource *r,
>   u32 __screen_info_lfb_bits_per_pixel(const struct screen_info *si);
>   
>   #if defined(CONFIG_PCI)
> +bool screen_info_is_useful(void);
>   void screen_info_apply_fixups(void);
>   struct pci_dev *screen_info_pci_dev(const struct screen_info *si);
>   #else
> +bool screen_info_is_useful(void)
> +{
> +	return true;
> +}
>   static inline void screen_info_apply_fixups(void)
>   { }
>   static inline struct pci_dev *screen_info_pci_dev(const struct screen_info *si)

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)