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| author |   Sam Ravnborg <sam@ravnborg.org> | 2020-07-09 21:30:16 +0200 |
|---|---|---|
| committer | Sam Ravnborg <sam@ravnborg.org> | 2020-07-27 16:47:46 +0200 |
| commit | 2a1658bf922ffd9b7907e270a7d9cdc9643fc45d (patch) | |
| tree | 6519b0e8c4b08dfe3ca96e6e8abdb13e6f15f4eb /include/drm | |
| parent | drm/mcde: Fix stability issue (diff) | |
| download | wireguard-linux-2a1658bf922ffd9b7907e270a7d9cdc9643fc45d.tar.xz wireguard-linux-2a1658bf922ffd9b7907e270a7d9cdc9643fc45d.zip | |
drm/drm_fb_helper: fix fbdev with sparc64
Recent kernels have been reported to panic using the bochs_drm
framebuffer under qemu-system-sparc64 which was bisected to
commit 7a0483ac4ffc ("drm/bochs: switch to generic drm fbdev emulation").
The backtrace indicates that the shadow framebuffer copy in
drm_fb_helper_dirty_blit_real() is trying to access the real
framebuffer using a virtual address rather than use an IO access
typically implemented using a physical (ASI_PHYS) access on SPARC.
The fix is to replace the memcpy with memcpy_toio() from io.h.
memcpy_toio() uses writeb() where the original fbdev code
used sbus_memcpy_toio(). The latter uses sbus_writeb().
The difference between writeb() and sbus_memcpy_toio() is
that writeb() writes bytes in little-endian, where sbus_writeb() writes
bytes in big-endian. As endian does not matter for byte writes they are
the same. So we can safely use memcpy_toio() here.
Note that this only fixes bochs, in general fbdev helpers still have
issues with mixing up system memory and __iomem space. Fixing that will
require a lot more work.
v3:
- Improved changelog (Daniel)
- Added FIXME to fbdev_use_iomem (Daniel)
v2:
- Added missing __iomem cast (kernel test robot)
- Made changelog readable and fix typos (Mark)
- Add flag to select iomem - and set it in the bochs driver
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reported-by: kernel test robot <lkp@intel.com>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200709193016.291267-1-sam@ravnborg.org
Link: https://patchwork.freedesktop.org/patch/msgid/20200725191012.GA434957@ravnborg.org
Diffstat (limited to 'include/drm')
| -rw-r--r-- | include/drm/drm_mode_config.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h index 6c3ef49b46b3..e73dea5c7333 100644 --- a/include/drm/drm_mode_config.h +++ b/include/drm/drm_mode_config.h @@ -866,6 +866,18 @@ struct drm_mode_config { bool prefer_shadow_fbdev; /** + * @fbdev_use_iomem: + * + * Set to true if framebuffer reside in iomem. + * When set to true memcpy_toio() is used when copying the framebuffer in + * drm_fb_helper.drm_fb_helper_dirty_blit_real(). + * + * FIXME: This should be replaced with a per-mapping is_iomem + * flag (like ttm does), and then used everywhere in fbdev code. + */ + bool fbdev_use_iomem; + + /** * @quirk_addfb_prefer_xbgr_30bpp: * * Special hack for legacy ADDFB to keep nouveau userspace happy. Should |