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It was reported that Weston stops at an assert, which checks that the page flip event timestamp is the same or newer than the previous timestamp: weston_output_finish_frame: Assertion `timespec_sub_to_nsec(stamp, &output->frame_time) >= 0' failed. With manual tests, I can see that when I enable the CRTC, I get a page flip event with a timestamp of 0. Tracking this down led to drm_reset_vblank_timestamp() which does "t_vblank = 0" if "high-precision query" is not available. TI DSS does not have any hardware timestamping, and thus the default ktime_get() is used in the DRM framework to get the vblank timestamp, and ktime_get() is not "high precision" here. It is not quite clear why the framework behaves this way, but I assume the idea is that drm_crtc_vblank_on(), which calls drm_reset_vblank_timestamp(), can be called at any time, and thus ktime_get() wouldn't give a good timestamp. And, the idea is that the driver would wait until next vblank after the CRTC enable, and then we could get a good timestamp. This is hinted in the comment: "reinitialize delayed at next vblank interrupt and assign 0 for now". I think that makes sense. However, when we enable the CRTC in TI DSS, i.e. we write the enable bit to the hardware, that's the exact moment when the "vblank cycle" starts. It is the zero point in the cycle, and thus ktime_get() would give a good timestamp. I am not sure if this is applicable to other hardware, and if so, how should it be solved in the framework. So, let's fix this in the tidss driver at least for now. This patch updates the vblank->time manually to ktime_get() just before sending the vblank event, and we enable the crtc just before calling ktime_get(). To get even more exact timing, the dispc_vp_enable() is moved inside the event_lock spinlock. With this, we get a proper timestamp for the page flip event from enabling the CRTC, and Weston is happy. Reviewed-by: Devarsh Thakkar <devarsht@ti.com> Link: https://patch.msgid.link/20250905-tidss-fix-timestamp-v1-2-c2aedf31e2c9@ideasonboard.com Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> Closes: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1553964/processor-sdk-am62x-weston-fails-to-wake-from-idle-time-sleep-restarts-after-sigterm Closes: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1416342/am625-am625-doesn-t-wake-up-from-standy-when-idle-time-is-configured-in-weston-ini |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.