Re: [PATCH 01/43] drm/fbdev-generic: Do not set physical framebuffer address

Thomas Zimmermann <tzimmermann@xxxxxxx> · Mon, 18 Mar 2024 08:59:01 +0100

Hi

Am 18.03.24 um 03:35 schrieb Zack Rusin:
On Tue, Mar 12, 2024 at 11:48 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
Framebuffer memory is allocated via vmalloc() from non-contiguous
physical pages. The physical framebuffer start address is therefore
meaningless. Do not set it.

The value is not used within the kernel and only exported to userspace
on dedicated ARM configs. No functional change is expected.

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Fixes: a5b44c4adb16 ("drm/fbdev-generic: Always use shadow buffering")
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Cc: Zack Rusin <zackr@xxxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v6.4+
---
  drivers/gpu/drm/drm_fbdev_generic.c | 1 -
  1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c
index d647d89764cb9..b4659cd6285ab 100644
--- a/drivers/gpu/drm/drm_fbdev_generic.c
+++ b/drivers/gpu/drm/drm_fbdev_generic.c
@@ -113,7 +113,6 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper,
         /* screen */
         info->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST;
         info->screen_buffer = screen_buffer;
-       info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer));
         info->fix.smem_len = screen_size;

         /* deferred I/O */
--
2.44.0

Good idea. I think given that drm_leak_fbdev_smem is off by default we
could remove the setting of smem_start by all of the in-tree drm
drivers (they all have open source userspace that won't mess around
with fbdev fb) - it will be reset to 0 anyway. Actually, I wonder if
we still need drm_leak_fbdev_smem at all...

All I know is that there's an embedded userspace driver that requires 
that setting. I don't even know which hardware.

Best regards
Thomas


Reviewed-by: Zack Rusin <zack.rusin@xxxxxxxxxxxx>

z

--
--
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)







