Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.7 40/79] drm/drm_fb_helper: fix fbdev with sparc64 | Date | Mon, 10 Aug 2020 17:20:59 +0200 |
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From: Sam Ravnborg <sam@ravnborg.org>
[ Upstream commit 2a1658bf922ffd9b7907e270a7d9cdc9643fc45d ]
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 Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/gpu/drm/bochs/bochs_kms.c | 1 + drivers/gpu/drm/drm_fb_helper.c | 6 +++++- include/drm/drm_mode_config.h | 12 ++++++++++++ 3 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c index 8066d7d370d5b..200d55fa97656 100644 --- a/drivers/gpu/drm/bochs/bochs_kms.c +++ b/drivers/gpu/drm/bochs/bochs_kms.c @@ -143,6 +143,7 @@ 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; diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index c7be39a00d437..4dd12a069474a 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -399,7 +399,11 @@ static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper, unsigned int y; for (y = clip->y1; y < clip->y2; y++) { - memcpy(dst, src, len); + if (!fb_helper->dev->mode_config.fbdev_use_iomem) + memcpy(dst, src, len); + else + memcpy_toio((void __iomem *)dst, src, len); + src += fb->pitches[0]; dst += fb->pitches[0]; } diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h index 3bcbe30339f04..198b9d0600081 100644 --- a/include/drm/drm_mode_config.h +++ b/include/drm/drm_mode_config.h @@ -865,6 +865,18 @@ 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: * -- 2.25.1
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