kernel.git/Documentation/gpu/todo.rst, branch linux-5.16.y

Revert "fbcon: Disable accelerated scrolling"

2022-02-08T17:35:11Z

commit 87ab9f6b7417349aa197a6c7098d4fdd4beebb74 upstream. This reverts commit 39aead8373b3c20bb5965c024dfb51a94e526151. Revert the first (of 2) commits which disabled scrolling acceleration in fbcon/fbdev. It introduced a regression for fbdev-supported graphic cards because of the performance penalty by doing screen scrolling by software instead of using the existing graphic card 2D hardware acceleration. Console scrolling acceleration was disabled by dropping code which checked at runtime the driver hardware capabilities for the BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move screen contents. After dropping those checks scrollmode was hard-wired to SCROLL_REDRAW instead, which forces all graphic cards to redraw every character at the new screen position when scrolling. This change effectively disabled all hardware-based scrolling acceleration for ALL drivers, because now all kind of 2D hardware acceleration (bitblt, fillrect) in the drivers isn't used any longer. The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm and gma500) used hardware acceleration in the past and thus code for checking and using scrolling acceleration is obsolete. This statement is NOT TRUE, because beside the DRM drivers there are around 35 other fbdev drivers which depend on fbdev/fbcon and still provide hardware acceleration for fbdev/fbcon. The original commit message also states that syzbot found lots of bugs in fbcon and thus it's "often the solution to just delete code and remove features". This is true, and the bugs - which actually affected all users of fbcon, including DRM - were fixed, or code was dropped like e.g. the support for software scrollback in vgacon (commit 973c096f6a85). So to further analyze which bugs were found by syzbot, I've looked through all patches in drivers/video which were tagged with syzbot or syzkaller back to year 2005. The vast majority fixed the reported issues on a higher level, e.g. when screen is to be resized, or when font size is to be changed. The few ones which touched driver code fixed a real driver bug, e.g. by adding a check. But NONE of those patches touched code of either the SCROLL_MOVE or the SCROLL_REDRAW case. That means, there was no real reason why SCROLL_MOVE had to be ripped-out and just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it could go away. That argument completely missed the fact that SCROLL_MOVE is still heavily used by fbdev (non-DRM) drivers. Some people mention that using memcpy() instead of the hardware acceleration is pretty much the same speed. But that's not true, at least not for older graphic cards and machines where we see speed decreases by factor 10 and more and thus this change leads to console responsiveness way worse than before. That's why the original commit is to be reverted. By reverting we reintroduce hardware-based scrolling acceleration and fix the performance regression for fbdev drivers. There isn't any impact on DRM when reverting those patches. Signed-off-by: Helge Deller Acked-by: Geert Uytterhoeven Acked-by: Sven Schnelle Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Helge Deller Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-3-deller@gmx.de Signed-off-by: Greg Kroah-Hartman

Revert "fbdev: Garbage collect fbdev scrolling acceleration, part 1 (from TODO list)"

2022-02-08T17:35:11Z

commit 1148836fd3226c20de841084aba24184d4fbbe77 upstream. This reverts commit b3ec8cdf457e5e63d396fe1346cc788cf7c1b578. Revert the second (of 2) commits which disabled scrolling acceleration in fbcon/fbdev. It introduced a regression for fbdev-supported graphic cards because of the performance penalty by doing screen scrolling by software instead of using the existing graphic card 2D hardware acceleration. Console scrolling acceleration was disabled by dropping code which checked at runtime the driver hardware capabilities for the BINFO_HWACCEL_COPYAREA or FBINFO_HWACCEL_FILLRECT flags and if set, it enabled scrollmode SCROLL_MOVE which uses hardware acceleration to move screen contents. After dropping those checks scrollmode was hard-wired to SCROLL_REDRAW instead, which forces all graphic cards to redraw every character at the new screen position when scrolling. This change effectively disabled all hardware-based scrolling acceleration for ALL drivers, because now all kind of 2D hardware acceleration (bitblt, fillrect) in the drivers isn't used any longer. The original commit message mentions that only 3 DRM drivers (nouveau, omapdrm and gma500) used hardware acceleration in the past and thus code for checking and using scrolling acceleration is obsolete. This statement is NOT TRUE, because beside the DRM drivers there are around 35 other fbdev drivers which depend on fbdev/fbcon and still provide hardware acceleration for fbdev/fbcon. The original commit message also states that syzbot found lots of bugs in fbcon and thus it's "often the solution to just delete code and remove features". This is true, and the bugs - which actually affected all users of fbcon, including DRM - were fixed, or code was dropped like e.g. the support for software scrollback in vgacon (commit 973c096f6a85). So to further analyze which bugs were found by syzbot, I've looked through all patches in drivers/video which were tagged with syzbot or syzkaller back to year 2005. The vast majority fixed the reported issues on a higher level, e.g. when screen is to be resized, or when font size is to be changed. The few ones which touched driver code fixed a real driver bug, e.g. by adding a check. But NONE of those patches touched code of either the SCROLL_MOVE or the SCROLL_REDRAW case. That means, there was no real reason why SCROLL_MOVE had to be ripped-out and just SCROLL_REDRAW had to be used instead. The only reason I can imagine so far was that SCROLL_MOVE wasn't used by DRM and as such it was assumed that it could go away. That argument completely missed the fact that SCROLL_MOVE is still heavily used by fbdev (non-DRM) drivers. Some people mention that using memcpy() instead of the hardware acceleration is pretty much the same speed. But that's not true, at least not for older graphic cards and machines where we see speed decreases by factor 10 and more and thus this change leads to console responsiveness way worse than before. That's why the original commit is to be reverted. By reverting we reintroduce hardware-based scrolling acceleration and fix the performance regression for fbdev drivers. There isn't any impact on DRM when reverting those patches. Signed-off-by: Helge Deller Acked-by: Geert Uytterhoeven Acked-by: Sven Schnelle Cc: stable@vger.kernel.org # v5.16+ Signed-off-by: Helge Deller Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220202135531.92183-2-deller@gmx.de Signed-off-by: Greg Kroah-Hartman

fbdev: Garbage collect fbdev scrolling acceleration, part 1 (from TODO list)

2021-10-13T13:29:23Z

Scroll acceleration is disabled in fbcon by hard-wiring p->scrollmode = SCROLL_REDRAW. Remove the obsolete code in fbcon.c and fbdev/core/ Signed-off-by: Claudio Suarez Signed-off-by: Thomas Zimmermann Link: https://patchwork.freedesktop.org/patch/msgid/YVXTYqszZix9TxjJ@gineta.localdomain

doc: drm: remove TODO entry regarding DRM_MODSET_LOCK_ALL cleanup

2021-10-01T17:01:05Z

The previous commits do exactly what this entry in the TODO file asks for, thus we can remove it now as it is no longer applicable. Signed-off-by: Fernando Ramos Reviewed-by: Sean Paul Signed-off-by: Sean Paul Link: https://patchwork.freedesktop.org/patch/msgid/20210924064324.229457-18-greenfoo@u92.eu

drm/todo: Add link to old debugfs RFC

2021-04-21T23:11:39Z

I always forget where it was, store it until this gets picked up by an internship again. Cc: Wambui Karuga Cc: Melissa Wen Acked-by: Melissa Wen Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210421152911.1871473-1-daniel.vetter@ffwll.ch

Merge drm/drm-next into drm-misc-next

2021-03-16T08:06:23Z

Noralf needs some patches in 5.12-rc3, and we've been delaying the 5.12 merge due to the swap issue so it looks like a good time. Signed-off-by: Maxime Ripard

Merge tag 'drm-misc-next-2021-03-03' of git://anongit.freedesktop.org/drm/drm-misc into drm-next

2021-03-16T07:08:46Z

drm-misc-next for 5.13: UAPI Changes: Cross-subsystem Changes: Core Changes: - %p4cc printk format modifier - atomic: introduce drm_crtc_commit_wait, rework atomic plane state helpers to take the drm_commit_state structure - dma-buf: heaps rework to return a struct dma_buf - simple-kms: Add plate state helpers - ttm: debugfs support, removal of sysfs Driver Changes: - Convert drivers to shadow plane helpers - arc: Move to drm/tiny - ast: cursor plane reworks - gma500: Remove TTM and medfield support - mxsfb: imx8mm support - panfrost: MMU IRQ handling rework - qxl: rework to better handle resources deallocation, locking - sun4i: Add alpha properties for UI and VI layers - vc4: RPi4 CEC support - vmwgfx: doc cleanup Signed-off-by: Dave Airlie From: Maxime Ripard Link: https://patchwork.freedesktop.org/patch/msgid/20210303100600.dgnkadonzuvfnu22@gilmour

drm: Use USB controller's DMA mask when importing dmabufs

2021-03-11T10:11:33Z

USB devices cannot perform DMA and hence have no dma_mask set in their device structure. Therefore importing dmabuf into a USB-based driver fails, which breaks joining and mirroring of display in X11. For USB devices, pick the associated USB controller as attachment device. This allows the DRM import helpers to perform the DMA setup. If the DMA controller does not support DMA transfers, we're out of luck and cannot import. Our current USB-based DRM drivers don't use DMA, so the actual DMA device is not important. Tested by joining/mirroring displays of udl and radeon under Gnome/X11. v8: * release dmadev if device initialization fails (Noralf) * fix commit description (Noralf) v7: * fix use-before-init bug in gm12u320 (Dan) v6: * implement workaround in DRM drivers and hold reference to DMA device while USB device is in use * remove dev_is_usb() (Greg) * collapse USB helper into usb_intf_get_dma_device() (Alan) * integrate Daniel's TODO statement (Daniel) * fix typos (Greg) v5: * provide a helper for USB interfaces (Alan) * add FIXME item to documentation and TODO list (Daniel) v4: * implement workaround with USB helper functions (Greg) * use struct usb_device->bus->sysdev as DMA device (Takashi) v3: * drop gem_create_object * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) v2: * move fix to importer side (Christian, Daniel) * update SHMEM and CMA helpers for new PRIME callbacks Signed-off-by: Thomas Zimmermann Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") Tested-by: Pavel Machek Reviewed-by: Greg Kroah-Hartman Acked-by: Christian König Acked-by: Daniel Vetter Acked-by: Noralf Trønnes Cc: Christoph Hellwig Cc: Greg Kroah-Hartman Cc: # v5.10+ Signed-off-by: Thomas Zimmermann Link: https://patchwork.freedesktop.org/patch/msgid/20210303133229.3288-1-tzimmermann@suse.de Signed-off-by: Maarten Lankhorst

docs: gpu: fix typo

2021-03-08T08:09:31Z

Signed-off-by: Jianhui Zhao Signed-off-by: Simon Ser Link: https://patchwork.freedesktop.org/patch/msgid/20210308064250.3681707-1-zhaojh329@gmail.com

drm/todo: Remove the drm_atomic_state todo item

2021-02-25T07:05:28Z

Only planes' prepare_fb and cleanup_fb, and encoders' atomic_check and atomic_mode_set hooks remain with an object state and not the global drm_atomic_state. prepare_fb and cleanup_fb operate by design on a given state and depending on the calling site can operate on either the old or new state, so it doesn't really make much sense to convert them. The encoders' atomic_check and atomic_mode_set operate on the CRTC and connector state connected to them since encoders don't have a state of their own. Without those state pointers, we would need to get the CRTC through the drm_connector_state crtc pointer. However, in order to get the drm_connector_state pointer, we would need to get the connector itself and while usually we have a single connector connected to the encoder, we can't really get it from the encoder at the moment since it could be behind any number of bridges. While this could be addressed by (for example) listing all the connectors and finding the one that has the encoder as its source, it feels like an unnecessary rework for something that is slowly getting replaced by bridges. Since all the users that matter have been converted, let's remove the TODO item. Acked-by: Daniel Vetter Signed-off-by: Maxime Ripard Acked-by: Thomas Zimmermann Link: https://patchwork.freedesktop.org/patch/msgid/20210219120032.260676-11-maxime@cerno.tech