Hi

Am 26.06.25 um 11:49 schrieb oushixiong1...@163.com:
From: Shixiong Ou <oushixi...@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


Signed-off-by: Shixiong Ou <oushixi...@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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