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| author | Sam Ravnborg <sam@ravnborg.org> | 2020-07-09 22:30:16 +0300 |
|---|---|---|
| committer | Sam Ravnborg <sam@ravnborg.org> | 2020-07-27 17:47:46 +0300 |
| commit | 2a1658bf922ffd9b7907e270a7d9cdc9643fc45d (patch) | |
| tree | 6519b0e8c4b08dfe3ca96e6e8abdb13e6f15f4eb /drivers/gpu/drm/bochs/bochs_kms.c | |
| parent | aa7bf898d4bf921f61fab078040e8baec3f28126 (diff) | |
| download | linux-2a1658bf922ffd9b7907e270a7d9cdc9643fc45d.tar.xz | |
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 'drivers/gpu/drm/bochs/bochs_kms.c')
| -rw-r--r-- | drivers/gpu/drm/bochs/bochs_kms.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c index 05d8373888e8..079f46f5cdb6 100644 --- a/drivers/gpu/drm/bochs/bochs_kms.c +++ b/drivers/gpu/drm/bochs/bochs_kms.c @@ -146,6 +146,7 @@ int bochs_kms_init(struct bochs_device *bochs) bochs->dev->mode_config.preferred_depth = 24; bochs->dev->mode_config.prefer_shadow = 0; bochs->dev->mode_config.prefer_shadow_fbdev = 1; + bochs->dev->mode_config.fbdev_use_iomem = true; bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true; bochs->dev->mode_config.funcs = &bochs_mode_funcs; |