Re: [PATCH] fbdev: efifb: do not load efifb if PCI BAR has changed but not fixuped
From: Thomas Zimmermann
Date: Fri Jun 27 2025 - 04:13:09 EST
Hi
Am 27.06.25 um 10:07 schrieb 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.
The patch's final revision had a rough development. Just for testing
purposes, could you revert the commit and instead apply the patch's
earlier revision from
https://patchwork.freedesktop.org/patch/649527/?series=148057&rev=1
?
Thanks a lot.
Best regards
Thomas
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)
--
--
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)