kernel/linux.git/drivers/gpu/drm/mgag200, branch v6.6.132

drm/mgag200: fix mgag200_bmc_stop_scanout()

2026-02-11T12:39:15+00:00

[ Upstream commit 0e0c8f4d16de92520623aa1ea485cadbf64e6929 ] The mgag200_bmc_stop_scanout() function is called by the .atomic_disable() handler for the MGA G200 VGA BMC encoder. This function performs a few register writes to inform the BMC of an upcoming mode change, and then polls to wait until the BMC actually stops. The polling is implemented using a busy loop with udelay() and an iteration timeout of 300, resulting in the function blocking for 300 milliseconds. The function gets called ultimately by the output_poll_execute work thread for the DRM output change polling thread of the mgag200 driver: kworker/0:0-mm_ 3528 [000] 4555.315364: ffffffffaa0e25b3 delay_halt.part.0+0x33 ffffffffc03f6188 mgag200_bmc_stop_scanout+0x178 ffffffffc087ae7a disable_outputs+0x12a ffffffffc087c12a drm_atomic_helper_commit_tail+0x1a ffffffffc03fa7b6 mgag200_mode_config_helper_atomic_commit_tail+0x26 ffffffffc087c9c1 commit_tail+0x91 ffffffffc087d51b drm_atomic_helper_commit+0x11b ffffffffc0509694 drm_atomic_commit+0xa4 ffffffffc05105e8 drm_client_modeset_commit_atomic+0x1e8 ffffffffc0510ce6 drm_client_modeset_commit_locked+0x56 ffffffffc0510e24 drm_client_modeset_commit+0x24 ffffffffc088a743 __drm_fb_helper_restore_fbdev_mode_unlocked+0x93 ffffffffc088a683 drm_fb_helper_hotplug_event+0xe3 ffffffffc050f8aa drm_client_dev_hotplug+0x9a ffffffffc088555a output_poll_execute+0x29a ffffffffa9b35924 process_one_work+0x194 ffffffffa9b364ee worker_thread+0x2fe ffffffffa9b3ecad kthread+0xdd ffffffffa9a08549 ret_from_fork+0x29 On a server running ptp4l with the mgag200 driver loaded, we found that ptp4l would sometimes get blocked from execution because of this busy waiting loop. Every so often, approximately once every 20 minutes -- though with large variance -- the output_poll_execute() thread would detect some sort of change that required performing a hotplug event which results in attempting to stop the BMC scanout, resulting in a 300msec delay on one CPU. On this system, ptp4l was pinned to a single CPU. When the output_poll_execute() thread ran on that CPU, it blocked ptp4l from executing for its 300 millisecond duration. This resulted in PTP service disruptions such as failure to send a SYNC message on time, failure to handle ANNOUNCE messages on time, and clock check warnings from the application. All of this despite the application being configured with FIFO_RT and a higher priority than the background workqueue tasks. (However, note that the kernel did not use CONFIG_PREEMPT...) It is unclear if the event is due to a faulty VGA connection, another bug, or actual events causing a change in the connection. At least on the system under test it is not a one-time event and consistently causes disruption to the time sensitive applications. The function has some helpful comments explaining what steps it is attempting to take. In particular, step 3a and 3b are explained as such: 3a - The third step is to verify if there is an active scan. We are waiting on a 0 on remhsyncsts (. 3b - This step occurs only if the remove is actually scanning. We are waiting for the end of the frame which is a 1 on remvsyncsts (). The actual steps 3a and 3b are implemented as while loops with a non-sleeping udelay(). The first step iterates while the tmp value at position 0 is *not* set. That is, it keeps iterating as long as the bit is zero. If the bit is already 0 (because there is no active scan), it will iterate the entire 300 attempts which wastes 300 milliseconds in total. This is opposite of what the description claims. The step 3b logic only executes if we do not iterate over the entire 300 attempts in the first loop. If it does trigger, it is trying to check and wait for a 1 on the remvsyncsts. However, again the condition is actually inverted and it will loop as long as the bit is 1, stopping once it hits zero (rather than the explained attempt to wait until we see a 1). Worse, both loops are implemented using non-sleeping waits which spin instead of allowing the scheduler to run other processes. If the kernel is not configured to allow arbitrary preemption, it will waste valuable CPU time doing nothing. There does not appear to be any documentation for the BMC register interface, beyond what is in the comments here. It seems more probable that the comment here is correct and the implementation accidentally got inverted from the intended logic. Reading through other DRM driver implementations, it does not appear that the .atomic_enable or .atomic_disable handlers need to delay instead of sleep. For example, the ast_astdp_encoder_helper_atomic_disable() function calls ast_dp_set_phy_sleep() which uses msleep(). The "atomic" in the name is referring to the atomic modesetting support, which is the support to enable atomic configuration from userspace, and not to the "atomic context" of the kernel. There is no reason to use udelay() here if a sleep would be sufficient. Replace the while loops with a read_poll_timeout() based implementation that will sleep between iterations, and which stops polling once the condition is met (instead of looping as long as the condition is met). This aligns with the commented behavior and avoids blocking on the CPU while doing nothing. Note the RREG_DAC is implemented using a statement expression to allow working properly with the read_poll_timeout family of functions. The other RREG_ macros ought to be cleaned up to have better semantics, and several places in the mgag200 driver could make use of RREG_DAC or similar RREG_* macros should likely be cleaned up for better semantics as well, but that task has been left as a future cleanup for a non-bugfix. Fixes: 414c45310625 ("mgag200: initial g200se driver (v2)") Suggested-by: Thomas Zimmermann Signed-off-by: Jacob Keller Reviewed-by: Thomas Zimmermann Reviewed-by: Jocelyn Falempe Signed-off-by: Thomas Zimmermann Link: https://patch.msgid.link/20260202-jk-mgag200-fix-bad-udelay-v2-1-ce1e9665987d@intel.com Signed-off-by: Sasha Levin

drm/mgag200: Fix big-endian support

2026-01-11T14:22:19+00:00

commit 6cb31fba137d45e682ce455b8ea364f44d5d4f98 upstream. Unlike the original, deleted Matrox mga driver, the new mgag200 driver has the XRGB frame-buffer byte swapped on big-endian "RISC" systems. Fix by enabling byte swapping "PowerPC" OPMODE for any __BIG_ENDIAN config. Fixes: 414c45310625 ("mgag200: initial g200se driver (v2)") Signed-off-by: René Rebe Cc: stable@kernel.org Reviewed-by: Thomas Zimmermann Signed-off-by: Thomas Zimmermann Link: https://patch.msgid.link/20251208.141827.965103015954471168.rene@exactco.de Signed-off-by: Greg Kroah-Hartman

drm/mgag200: Bind I2C lifetime to DRM device

2024-08-14T11:59:01+00:00

commit eb1ae34e48a09b7a1179c579aed042b032e408f4 upstream. Managed cleanup with devm_add_action_or_reset() will release the I2C adapter when the underlying Linux device goes away. But the connector still refers to it, so this cleanup leaves behind a stale pointer in struct drm_connector.ddc. Bind the lifetime of the I2C adapter to the connector's lifetime by using DRM's managed release. When the DRM device goes away (after the Linux device) DRM will first clean up the connector and then clean up the I2C adapter. Signed-off-by: Thomas Zimmermann Reviewed-by: Jocelyn Falempe Fixes: b279df242972 ("drm/mgag200: Switch I2C code to managed cleanup") Cc: Thomas Zimmermann Cc: Jocelyn Falempe Cc: Dave Airlie Cc: dri-devel@lists.freedesktop.org Cc: # v6.0+ Link: https://patchwork.freedesktop.org/patch/msgid/20240513125620.6337-3-tzimmermann@suse.de Signed-off-by: Greg Kroah-Hartman

drm/mgag200: Set DDC timeout in milliseconds

2024-08-14T11:59:01+00:00

commit ecde5db1598aecab54cc392282c15114f526f05f upstream. Compute the i2c timeout in jiffies from a value in milliseconds. The original values of 2 jiffies equals 2 milliseconds if HZ has been configured to a value of 1000. This corresponds to 2.2 milliseconds used by most other DRM drivers. Update mgag200 accordingly. Signed-off-by: Thomas Zimmermann Reviewed-by: Jocelyn Falempe Fixes: 414c45310625 ("mgag200: initial g200se driver (v2)") Cc: Dave Airlie Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: Jocelyn Falempe Cc: dri-devel@lists.freedesktop.org Cc: # v3.5+ Link: https://patchwork.freedesktop.org/patch/msgid/20240513125620.6337-2-tzimmermann@suse.de Signed-off-by: Greg Kroah-Hartman

drm/mgag200: Fix gamma lut not initialized for G200ER, G200EV, G200SE

2024-01-10T16:16:46+00:00

commit 11f9eb899ecc8c02b769cf8d2532ba12786a7af7 upstream. When mgag200 switched from simple KMS to regular atomic helpers, the initialization of the gamma settings was lost. This leads to a black screen, if the bios/uefi doesn't use the same pixel color depth. This has been fixed with commit ad81e23426a6 ("drm/mgag200: Fix gamma lut not initialized.") for most G200, but G200ER, G200EV, G200SE use their own version of crtc_helper_atomic_enable() and need to be fixed too. Fixes: 1baf9127c482 ("drm/mgag200: Replace simple-KMS with regular atomic helpers") Cc: #v6.1+ Reported-by: Roger Sewell Suggested-by: Roger Sewell Signed-off-by: Jocelyn Falempe Reviewed-by: Thomas Zimmermann Link: https://patchwork.freedesktop.org/patch/msgid/20231214163849.359691-1-jfalempe@redhat.com Signed-off-by: Greg Kroah-Hartman

drm: Call drm_atomic_helper_shutdown() at shutdown/remove time for misc drivers

2023-11-20T10:59:10+00:00

[ Upstream commit 3c4babae3c4a1ae05f8f3f5f3d50c440ead7ca6a ] Based on grepping through the source code these drivers appear to be missing a call to drm_atomic_helper_shutdown() at system shutdown time and at driver remove (or unbind) time. Among other things, this means that if a panel is in use that it won't be cleanly powered off at system shutdown time. The fact that we should call drm_atomic_helper_shutdown() in the case of OS shutdown/restart and at driver remove (or unbind) time comes straight out of the kernel doc "driver instance overview" in drm_drv.c. A few notes about these fixes: - I confirmed that these drivers were all DRIVER_MODESET type drivers, which I believe makes this relevant. - I confirmed that these drivers were all DRIVER_ATOMIC. - When adding drm_atomic_helper_shutdown() to the remove/unbind path, I added it after drm_kms_helper_poll_fini() when the driver had it. This seemed to be what other drivers did. If drm_kms_helper_poll_fini() wasn't there I added it straight after drm_dev_unregister(). - This patch deals with drivers using the component model in similar ways as the patch ("drm: Call drm_atomic_helper_shutdown() at shutdown time for misc drivers") - These fixes rely on the patch ("drm/atomic-helper: drm_atomic_helper_shutdown(NULL) should be a noop") to simplify shutdown. Suggested-by: Maxime Ripard Reviewed-by: Tomi Valkeinen Tested-by: Tomi Valkeinen # tilcdc Acked-by: Maxime Ripard Signed-off-by: Douglas Anderson Link: https://patchwork.freedesktop.org/patch/msgid/20230901163944.RFT.5.I771eb4bd03d8772b19e7dcfaef3e2c167bce5846@changeid Signed-off-by: Sasha Levin

drm/mgag200: set variable mgag200_modeset storage-class-specifier to static

2023-06-23T08:33:00+00:00

smatch reports drivers/gpu/drm/mgag200/mgag200_drv.c:23:5: warning: symbol 'mgag200_modeset' was not declared. Should it be static? This variable is only used in its defining file, so it should be static Signed-off-by: Tom Rix Reviewed-by: Jocelyn Falempe Reviewed-by: Thomas Zimmermann Signed-off-by: Jocelyn Falempe Link: https://patchwork.freedesktop.org/patch/msgid/20230517134140.874179-1-trix@redhat.com

Merge drm/drm-fixes into drm-misc-fixes

2023-05-12T07:47:12+00:00

Let's bring 6.4-rc1 in drm-misc-fixes to start the new fix cycle. Signed-off-by: Maxime Ripard

drm/mgag200: Fix gamma lut not initialized.

2023-05-11T13:20:11+00:00

When mgag200 switched from simple KMS to regular atomic helpers, the initialization of the gamma settings was lost. This leads to a black screen, if the bios/uefi doesn't use the same pixel color depth. v2: rebase on top of drm-misc-fixes, and add Cc stable tag. Link: https://bugzilla.redhat.com/show_bug.cgi?id=2171155 Fixes: 1baf9127c482 ("drm/mgag200: Replace simple-KMS with regular atomic helpers") Cc: Tested-by: Phil Oester Reviewed-by: Thomas Zimmermann Signed-off-by: Jocelyn Falempe Link: https://patchwork.freedesktop.org/patch/msgid/20230510131034.284078-1-jfalempe@redhat.com

drm/mgag200: Implement struct drm_plane_helper_funcs.atomic_enable

2023-02-20T14:20:41+00:00

Enable the primary plane for mgag200 hardware via atomic_enable. Atomic helpers invoke this callback only when the plane becomes active. Signed-off-by: Thomas Zimmermann Reviewed-by: Javier Martinez Canillas Link: https://patchwork.freedesktop.org/patch/msgid/20230209154107.30680-5-tzimmermann@suse.de