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

[Shixiong Ou]

在 2025/6/26 18:31, Thomas Zimmermann 写道:
> Hi
>
> Am 26.06.25 um 11:49 schrieb oushixiong1025@xxxxxxx:
> > From: Shixiong Ou <oushixiong@xxxxxxxxxx>
> >
> > [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
yeah, this patch is in my tree. but do not fix the problem.

this is some message:

kylin@kylin-pc:~$ dmesg | grep BAR
[    0.688192] pci 0000:00:03.0: BAR 15: assigned [mem 
0x1000000000-0x101fffffff 64bit pref]
[    0.688200] pci 0000:00:00.0: BAR 0: assigned [mem 
0x1020000000-0x10200fffff 64bit pref]
[    0.688205] pci 0000:00:00.0: BAR 14: assigned [mem 
0x58000000-0x580fffff]
[    0.688210] pci 0000:00:01.0: BAR 0: assigned [mem 
0x1020100000-0x10201fffff 64bit pref]
[    0.688215] pci 0000:00:02.0: BAR 0: assigned [mem 
0x1020200000-0x10202fffff 64bit pref]
[    0.688221] pci 0000:00:02.0: BAR 14: assigned [mem 
0x58100000-0x581fffff]
[    0.688225] pci 0000:00:03.0: BAR 0: assigned [mem 
0x1020300000-0x10203fffff 64bit pref]
[    0.688231] pci 0000:00:03.0: BAR 14: assigned [mem 
0x58200000-0x585fffff]
[    0.688237] pci 0000:00:04.0: BAR 0: assigned [mem 
0x1020400000-0x10204fffff 64bit pref]
[    0.688243] pci 0000:00:05.0: BAR 0: assigned [mem 
0x1020500000-0x10205fffff 64bit pref]
[    0.688249] pci 0000:00:05.0: BAR 14: assigned [mem 
0x58600000-0x586fffff]
[    0.688253] pci 0000:01:00.0: BAR 0: assigned [mem 
0x58000000-0x58003fff 64bit]
[    0.688290] pci 0000:03:00.0: BAR 6: assigned [mem 
0x58100000-0x5817ffff pref]
[    0.688296] pci 0000:03:00.0: BAR 0: assigned [mem 0x58180000-0x58181fff]
[    0.688303] pci 0000:03:00.0: BAR 5: assigned [mem 0x58182000-0x58183fff]
[    0.688317] pci 0000:04:00.0: BAR 1: assigned [mem 
0x1000000000-0x101fffffff 64bit pref]
[    0.688326] pci 0000:04:00.0: BAR 0: assigned [mem 0x58200000-0x583fffff]
[    0.688332] pci 0000:04:00.0: BAR 6: assigned [mem 
0x58400000-0x584fffff pref]
[    0.688336] pci 0000:04:00.1: BAR 0: assigned [mem 0x58500000-0x58503fff]
[    0.688360] pci 0000:06:00.0: BAR 0: assigned [mem 
0x58600000-0x58601fff 64bit]
kylin@kylin-pc:~$ dmesg | grep framebuffer
[    1.137536] efifb: framebuffer at 0x1020000000, using 3072k, total 3072k

the efifb base address is still at 0x1020000000 after calling 
pcibios_bus_to_resource().


> > 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@xxxxxxxxxx>
> > ---
> >   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");

And should something be done after __screen_info_relocation_is_valid() 
return false?

Best regards
Shixiong.

> >               }
> >           }
> > +    } 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)