[PATCH] fbdev: efifb: do not load efifb if PCI BAR has changed but not fixuped
Thomas Zimmermann
tzimmermann at suse.de
Mon Jul 7 09:28:32 UTC 2025
Hi
Am 07.07.25 um 11:24 schrieb Shixiong Ou:
>
> 在 2025/6/27 17:13, Thomas Zimmermann 写道:
>> Hi
>>
>> Am 26.06.25 um 11:49 schrieb oushixiong1025 at 163.com:
>>> From: Shixiong Ou <oushixiong at 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
>>> 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.
>>
>> Apart from ruling out invalid screen_info, did you figure out why the
>> relocation tracking didn't work? It would be good to fix this if
>> possible.
>>
>> Best regards
>> Thomas
>>
> I haven’t figure out the root cause yet.
>
> This issue is quite rare and might be related to the EFI firmware.
> However, I wonder if we could add some handling when no PCI resources
> are found in screen_info_fixup_lfb(), as a temporary workaround for
> the problem I mentioned earlier.
As I said elsewhere in the thread, you can clear the screen_info's video
type in the branch at [1] to disable it entirely. We should have
probably done this anyway. Knowing the cause of the issue would still be
nice though.
Best regards
Thomas
[1]
https://elixir.bootlin.com/linux/v6.15.5/source/drivers/video/screen_info_pci.c#L44
>
> Best regards
> Shixiong Ou
>
>>>
>>> Signed-off-by: Shixiong Ou <oushixiong at 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)
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