linux-toradex.git/drivers/gpu/drm/mgag200/mgag200_drv.h, branch v6.19 Linux kernel for Apalis and Colibri modules drm/mgag200: fix mgag200_bmc_stop_scanout() 2026-02-04T07:52:53+00:00 Jacob Keller jacob.e.keller@intel.com 2026-02-03T00:16:39+00:00 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 (<XSPAREREG<0>. 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 (<XSPAREREG<1>). 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_<TYPE> 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 <tzimmermann@suse.de> Signed-off-by: Jacob Keller <jacob.e.keller@intel.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Link: https://patch.msgid.link/20260202-jk-mgag200-fix-bad-udelay-v2-1-ce1e9665987d@intel.com 
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 (<XSPAREREG<0>.

  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
       (<XSPAREREG<1>).

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_<TYPE> 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 <tzimmermann@suse.de>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20260202-jk-mgag200-fix-bad-udelay-v2-1-ce1e9665987d@intel.com
drm/mgag200: Use helpers for programming gamma ramps 2025-05-26T07:19:24+00:00 Thomas Zimmermann tzimmermann@suse.de 2025-05-20T09:40:05+00:00 1bdb883d6574408e81caac6a09f86955687680a2 Replace mgag200's code for programming the hardware gamma LUT with DRM helpers. Either load a provided gamma ramp or program a default. Set the individual entries with a callback. Each gamma value is given as 3 individual 16-bit values for red, green and blue. The driver reduces them to 8 bit to make them fit into hardware registers. v2: - fix coding style Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://lore.kernel.org/r/20250520094203.30545-4-tzimmermann@suse.de 
Replace mgag200's code for programming the hardware gamma LUT with
DRM helpers. Either load a provided gamma ramp or program a default.
Set the individual entries with a callback.

Each gamma value is given as 3 individual 16-bit values for red,
green and blue. The driver reduces them to 8 bit to make them fit
into hardware registers.

v2:
- fix coding style

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250520094203.30545-4-tzimmermann@suse.de
drm/mgag200: Added support for the new device G200eH5 2025-02-11T09:53:53+00:00 Gwenael Georgeault ggeorgea@matrox.com 2025-02-07T19:04:29+00:00 6636c58b946c9cbfbd68a453d4eba2ef4585c65c - Added the new device ID - Added new pll algorithm Signed-off-by: Gwenael Georgeault <ggeorgea@matrox.com> Co-authored-by: Mamadou Insa Diop <mdiop@matrox.com> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/alpine.LFD.2.00.2502071401180.14188@pluton.matrox.com 
- Added the new device ID
- Added new pll algorithm

Signed-off-by: Gwenael Georgeault <ggeorgea@matrox.com>
Co-authored-by: Mamadou Insa Diop <mdiop@matrox.com>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/alpine.LFD.2.00.2502071401180.14188@pluton.matrox.com
drm: remove driver date from struct drm_driver and all drivers 2024-12-05T10:35:42+00:00 Jani Nikula jani.nikula@intel.com 2024-12-04T14:31:12+00:00 cb2e1c2136f71618142557ceca3a8802e87a44cd We stopped using the driver initialized date in commit 7fb8af6798e8 ("drm: deprecate driver date") and (eventually) started returning "0" for drm_version ioctl instead. Finish the job, and remove the unused date member from struct drm_driver, its initialization from drivers, along with the common DRIVER_DATE macros. v2: Also update drivers/accel (kernel test robot) Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> Acked-by: Alex Deucher <alexander.deucher@amd.com> Acked-by: Simon Ser <contact@emersion.fr> Acked-by: Jeffrey Hugo <quic_jhugo@quicinc.com> Acked-by: Lucas De Marchi <lucas.demarchi@intel.com> Acked-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> # msm Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> Link: https://patchwork.freedesktop.org/patch/msgid/1f2bf2543aed270a06f6c707fd6ed1b78bf16712.1733322525.git.jani.nikula@intel.com Signed-off-by: Jani Nikula <jani.nikula@intel.com> 
We stopped using the driver initialized date in commit 7fb8af6798e8
("drm: deprecate driver date") and (eventually) started returning "0"
for drm_version ioctl instead.

Finish the job, and remove the unused date member from struct
drm_driver, its initialization from drivers, along with the common
DRIVER_DATE macros.

v2: Also update drivers/accel (kernel test robot)

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Simon Ser <contact@emersion.fr>
Acked-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org> # msm
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1f2bf2543aed270a06f6c707fd6ed1b78bf16712.1733322525.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Revert "drm/mgag200: Add vblank support" 2024-10-17T06:49:45+00:00 Thomas Zimmermann tzimmermann@suse.de 2024-10-15T06:37:13+00:00 e5a3c24bcaf7bc1c3c2647395aae5de4660c1c64 This reverts commit 6c9e14ee9f519ee605a3694fbfa4711284781d22. This reverts commit d5070c9b29440c270b534bbacd636b8fa558e82b. This reverts commit 89c6ea2006e2d39b125848fb0195c08fa0b354be. The VLINE interrupt doesn't work correctly on G200SE-A (at least). We have also seen missing interrupts on G200ER. So revert vblank support. Fixes frozen displays and warnings about missed vblanks. [ 33.818362] [CRTC:34:crtc-0] vblank wait timed out From the vblank code, the driver only keeps the register constants and the line that disables all interrupts in mgag200_device_init(). Both is still useful without vblank handling. Reported-by: Tony Luck <tony.luck@intel.com> Closes: https://lore.kernel.org/dri-devel/Zvx6lSi7oq5xvTZb@agluck-desk3.sc.intel.com/raw Tested-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241015063932.8620-1-tzimmermann@suse.de 
This reverts commit 6c9e14ee9f519ee605a3694fbfa4711284781d22.
This reverts commit d5070c9b29440c270b534bbacd636b8fa558e82b.
This reverts commit 89c6ea2006e2d39b125848fb0195c08fa0b354be.

The VLINE interrupt doesn't work correctly on G200SE-A (at least). We
have also seen missing interrupts on G200ER. So revert vblank support.
Fixes frozen displays and warnings about missed vblanks.

[   33.818362] [CRTC:34:crtc-0] vblank wait timed out

From the vblank code, the driver only keeps the register constants and
the line that disables all interrupts in mgag200_device_init(). Both
is still useful without vblank handling.

Reported-by: Tony Luck <tony.luck@intel.com>
Closes: https://lore.kernel.org/dri-devel/Zvx6lSi7oq5xvTZb@agluck-desk3.sc.intel.com/raw
Tested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241015063932.8620-1-tzimmermann@suse.de
drm/mgag200: Remove BMC output 2024-08-09T06:13:48+00:00 Thomas Zimmermann tzimmermann@suse.de 2024-08-05T13:06:01+00:00 219b45d023ed0902b05c5902a4f31c2c38bcf68c Mgag200's BMC connector tracks the status of an underlying physical connector and updates the BMC status accordingly. This functionality works around GNOME's settings app, which cannot handle multiple outputs on the same CRTC. The workaround is now obsolete as the VGA-BMC connector handles BMC support internally. Hence, remove the driver's code and the BMC output entirely. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240805130622.63458-6-tzimmermann@suse.de 
Mgag200's BMC connector tracks the status of an underlying physical
connector and updates the BMC status accordingly. This functionality
works around GNOME's settings app, which cannot handle multiple
outputs on the same CRTC.

The workaround is now obsolete as the VGA-BMC connector handles BMC
support internally. Hence, remove the driver's code and the BMC output
entirely.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240805130622.63458-6-tzimmermann@suse.de
drm/mgag200: Add VGA-BMC output 2024-08-09T06:13:45+00:00 Thomas Zimmermann tzimmermann@suse.de 2024-08-05T13:05:57+00:00 f5510726608fa035bdd2f1fc167cf4a0f7bee22b Duplicate VGA output to VGA-BMC output and update all code for Matrox server chips. The new output represents a VGA output that has a BMC attached to it. No functional changes so far. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240805130622.63458-2-tzimmermann@suse.de 
Duplicate VGA output to VGA-BMC output and update all code for Matrox
server chips. The new output represents a VGA output that has a BMC
attached to it. No functional changes so far.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240805130622.63458-2-tzimmermann@suse.de
drm/mgag200: Implement struct drm_crtc_funcs.get_vblank_timestamp 2024-07-19T09:12:19+00:00 Thomas Zimmermann tzimmermann@suse.de 2024-07-18T10:44:17+00:00 d5070c9b29440c270b534bbacd636b8fa558e82b Implement struct drm_crtc_funcs.get_vblank_timestamp with the DRM helper drm_crtc_vblank_helper_get_vblank_timestamp() with its helper get_scanout_position. Read the scanout position from the MGAREG_VCOUNT register. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240718104551.575912-8-tzimmermann@suse.de 
Implement struct drm_crtc_funcs.get_vblank_timestamp with the DRM
helper drm_crtc_vblank_helper_get_vblank_timestamp() with its helper
get_scanout_position. Read the scanout position from the MGAREG_VCOUNT
register.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240718104551.575912-8-tzimmermann@suse.de
drm/mgag200: Add vblank support 2024-07-19T09:12:04+00:00 Thomas Zimmermann tzimmermann@suse.de 2024-07-18T10:44:16+00:00 89c6ea2006e2d39b125848fb0195c08fa0b354be There's no VBLANK interrupt on Matrox chipsets. The workaround that is being used here and in other free Matrox drivers is to program <linecomp> to the value of <vblkstr> and enable the VLINE interrupt. This triggers an interrupt at the time when VBLANK begins. VLINE uses separate registers for enabling and clearing pending interrupts. No extra synchronization between irq handler and the rest of the driver is required. v6: - clear VLINE status bit before registering IRQ (Jocelyn) v5: - disable all interrupts before registering IRQ (Jocelyn) - don't read from ICLEAR (Jocelyn) v4: - recreate patch on latest upstream - use devm_request_irq() for managed cleanup - fail if vblanking cannot be initialized - rename register constants (Sam, Emil) - clear interrupt before registering handler (Ville) - move <linecomp> programming into separate commit - set <linecomp> to <vblkstr> - fix typo in commit message v3: - set <linecomp> to <vdisplay> + 1 to trigger at VBLANK - expand comment on linecomp v2: - only signal vblank on CRTC 0 - use constants for registers and fields - set VLINECLR before enabling interrupt - test against STATUS and IEN in irq handler - coding-style fixes Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Acked-by: Gerd Hoffmann <kraxel@redhat.com> Acked-by: Sam Ravnborg <sam@ravnborg.org> Tested-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240718104551.575912-7-tzimmermann@suse.de 
There's no VBLANK interrupt on Matrox chipsets. The workaround that is
being used here and in other free Matrox drivers is to program <linecomp>
to the value of <vblkstr> and enable the VLINE interrupt. This triggers
an interrupt at the time when VBLANK begins.

VLINE uses separate registers for enabling and clearing pending interrupts.
No extra synchronization between irq handler and the rest of the driver is
required.

v6:
- clear VLINE status bit before registering IRQ (Jocelyn)

v5:
- disable all interrupts before registering IRQ (Jocelyn)
- don't read from ICLEAR (Jocelyn)

v4:
- recreate patch on latest upstream
- use devm_request_irq() for managed cleanup
- fail if vblanking cannot be initialized
- rename register constants (Sam, Emil)
- clear interrupt before registering handler (Ville)
- move <linecomp> programming into separate commit
- set <linecomp> to <vblkstr>
- fix typo in commit message

v3:
- set <linecomp> to <vdisplay> + 1 to trigger at VBLANK
- expand comment on linecomp

v2:
- only signal vblank on CRTC 0
- use constants for registers and fields
- set VLINECLR before enabling interrupt
- test against STATUS and IEN in irq handler
- coding-style fixes

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240718104551.575912-7-tzimmermann@suse.de
drm/mgag200: Rename BMC vidrst names 2024-07-15T06:17:18+00:00 Thomas Zimmermann tzimmermann@suse.de 2024-07-11T07:23:06+00:00 3ac9384061b250ee40eda5facff10b85e2d5d3d8 The BMC's scanout synchronization is only indirectly related to the VIDRST functionality. Do some renaming. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240711072415.11831-4-tzimmermann@suse.de 
The BMC's scanout synchronization is only indirectly related to the
VIDRST functionality. Do some renaming.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240711072415.11831-4-tzimmermann@suse.de