Hi Doug,
On Wed, Oct 27, 2021 at 3:08 PM Doug Anderson dianders@chromium.org wrote:
Hi,
On Tue, Oct 26, 2021 at 2:56 PM Philip Chen philipchen@chromium.org wrote:
Fit ps8640 driver into runtime power management framework:
First, break _poweron() to 3 parts: (1) turn on power and wait for ps8640's internal MCU to finish init (2) check panel HPD (which is proxied by GPIO9) (3) the other configs. As runtime_resume() can be called before panel is powered, we only add (1) to _resume() and leave (2)(3) to _pre_enable(). We also add (2) to _aux_transfer() as we want to ensure panel HPD is asserted before we start AUX CH transactions.
Second, the original driver has a mysterious delay of 50 ms between (2) and (3). Since Parade's support can't explain what the delay is for, and we don't see removing the delay break any boards at hand, remove the delay to fit into this driver change.
In addition, rename "powered" to "pre_enabled" and don't check for it in the pm_runtime calls. The pm_runtime calls are already refcounted so there's no reason to check there. The other user of "powered", _get_edid(), only cares if pre_enable() has already been called.
Lastly, change some existing DRM_...() logging to dev_...() along the way, since DRM_...() seem to be deprecated in [1].
[1] https://patchwork.freedesktop.org/patch/454760/
Signed-off-by: Philip Chen philipchen@chromium.org Reviewed-by: Douglas Anderson dianders@chromium.org Reviewed-by: Stephen Boyd swboyd@chromium.org
In v3, I also added pm_suspend_ignore_children() in the ps8640_probe() but forgot to mention that in the v3 change log.
Changes in v4:
- Make ps8640_ensure_hpd() return int (This change was mis-added to another patch [2] in this patch series: [2] https://patchwork.kernel.org/project/dri-devel/patch/20211026121058.v3.2.I09...)
Changes in v3:
- Fix typo/wording in the commit message.
- Add ps8640_aux_transfer_msg() for AUX operation. In ps8640_aux_transfer(), wrap around ps8640_aux_transfer_msg() with PM operations and HPD check.
- Document why autosuspend_delay is set to 500ms.
drivers/gpu/drm/bridge/parade-ps8640.c | 186 +++++++++++++++---------- 1 file changed, 115 insertions(+), 71 deletions(-)
Unfortunately, your patch no longer applies to drm-misc/drm-misc-next. Commit 7abbc26fd667 ("drm/bridge: ps8640: Register and attach our DSI device at probe") landed and that causes a merge conflict. Can you rebase and resend?
Yes, I will rebase and resend.
This will also cause a conflict when Sam's change lands [1] so I guess we can see whose lands first. Let me review that now and maybe you add a Tested-by? If it lands that'll make it easier and you can just rebase on both of them?
As per your latest reply, I'll just rebase atop drm-misc-next for now.
pm_runtime_enable(dev);/** In practice, ps8640_aux_transfer_msg() takes ~300ms to complete in* the worst case. Set autosuspend_delay to 500ms.*/pm_runtime_set_autosuspend_delay(dev, 500);To be a little nitpicky, this makes it sound as if the 500 ms needs to be greater than the 300 ms for correctness. That's not _really_ the case. During the whole ps8640_aux_transfer_msg() we're holding a PM Runtime reference (so it won't autosuspend no matter what) and at the end of it we mark that we were busy so the timer won't start ticking until then.
Yeah....sorry, looking again, I agree the comment I added in v3 is pretty misleading. I think autosuspend_delay just needs to be consistently longer than the interval between each aux_transfer call during EDID read. I'll measure the interval and add the number to the comment.
Really the 500 ms is because we're quite slow to power up (~300 ms) and so we want to avoid powering down and powering up constantly. We definitely need to avoid a power down / power up when reading the EDID and an EDID read involves _several_ calls in a row to the AUX transfer function. We also expect that after userspace reads the EDID it will call us again "soon" to turn the power on and it's nice to not have to wait the 300 ms again. The 500 ms here is really just a number that's not too short but not too long. I suppose it's roughly related to the 300 ms because that's the delay we're trying to avoid, but otherwise they are unrelated. NOTE: the code will still be _correct_ if we miss the 500 ms window, it'll just be a lot slower.
[1] https://lore.kernel.org/r/20211020181901.2114645-2-sam@ravnborg.org
-Doug