Re: [PATCH v4 00/11] drm/panel and i2c-hid: Allow panels and touchscreens to power sequence together

[Benjamin Tissoires]

On Jul 27 2023, Douglas Anderson wrote:
> 
> The big motivation for this patch series is mostly described in the patch
> ("drm/panel: Add a way for other devices to follow panel state"), but to
> quickly summarize here: for touchscreens that are connected to a panel we
> need the ability to power sequence the two device together. This is not a
> new need, but so far we've managed to get by through a combination of
> inefficiency, added costs, or perhaps just a little bit of brokenness.
> It's time to do better. This patch series allows us to do better.
> 
> Assuming that people think this patch series looks OK, we'll have to
> figure out the right way to land it. The panel patches and i2c-hid
> patches will go through very different trees and so either we'll need
> an Ack from one side or the other or someone to create a tag for the
> other tree to pull in. This will _probably_ require the true drm-misc
> maintainers to get involved, not a lowly committer. ;-)
> 
> Version 4 of this series adds a new patch that suspends i2c-hid
> devices at remove time even for non panel-followers to make things
> consistent. It also attempts to isolate the panel follower code a bit
> more as per Benjamin's feedback on v3 and adds an item to the DRM todo
> list as per Maxime's request. As per Maxime's response to my v3 cover
> letter, I added his Reviewed-by tag to all 10 patches that were part
> of v3 (but left it off of the new i2c-hid patch in v4).
> 
> Version 3 of this series was a long time coming after v2. Maxime and I
> had a very long discussion trying to figure out if there was a beter
> way and in the end we didn't find one so he was OK with the series in
> general [1]. After that got resolved, I tried to resolve Benjamin's
> feedback but got stuck [2]. Eventually I made my best guess. The end
> result was a v3 that wasn't that different from v2 but that had a tiny
> bit more code split out.
> 
> Version 2 of this patch series didn't change too much. At a high level:
> * I added all the forgotten "static" to functions.
> * I've hopefully made the bindings better.
> * I've integrated into fw_devlink.
> * I cleaned up a few descriptions / comments.
> 
> As far as I can tell, as of v4 everyone is on the same page that this
> patch series looks like a reasonable solution to the problem and we
> just need to get all the nits fixed and figure out how to land it.

Thanks a lot for the new version. I like it much more on the HID side:

for the HID part:
Reviewed-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>

I wouldn't mind having this series taken from the drm tree if that is
easier. i2c-hid is a low patch rate driver, so having it updated through
DRM should not be an issue.

In that case:
Acked-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>

Cheers,
Benjamin

> 
> [1] https://lore.kernel.org/r/gkwymmfkdy2p2evz22wmbwgw42ii4wnvmvu64m3bghmj2jhv7x@4mbstjxnagxd
> [2] https://lore.kernel.org/r/CAD=FV=VbdeomBGbWhppY+5TOSwt64GWBHga68OXFwsnO4gg4UA@xxxxxxxxxxxxxx
> 
> Changes in v4:
> - Document further cleanup in the official DRM todo list.
> - ("Suspend i2c-hid devices in remove") new for v4.
> - Move panel follower alternative checks to wrapper functions.
> - Rebase atop ("Suspend i2c-hid devices in remove").
> 
> Changes in v3:
> - Add is_panel_follower() as a convenience for clients.
> - Add "depends on DRM || !DRM" to Kconfig to avoid randconfig error.
> - Split more of the panel follower code out of the core.
> 
> Changes in v2:
> - Move the description to the generic touchscreen.yaml.
> - Update the desc to make it clearer it's only for integrated devices.
> - Add even more text to the commit message.
> - A few comment cleanups.
> - ("Add a devlink for panel followers") new for v2.
> - i2c_hid_core_initial_power_up() is now static.
> - i2c_hid_core_panel_prepared() and ..._unpreparing() are now static.
> - ihid_core_panel_prepare_work() is now static.
> - Improve documentation for smp_wmb().
> 
> Douglas Anderson (11):
>   dt-bindings: HID: i2c-hid: Add "panel" property to i2c-hid backed
>     touchscreens
>   drm/panel: Check for already prepared/enabled in drm_panel
>   drm/panel: Add a way for other devices to follow panel state
>   of: property: fw_devlink: Add a devlink for panel followers
>   HID: i2c-hid: Switch to SYSTEM_SLEEP_PM_OPS()
>   HID: i2c-hid: Rearrange probe() to power things up later
>   HID: i2c-hid: Make suspend and resume into helper functions
>   HID: i2c-hid: Suspend i2c-hid devices in remove
>   HID: i2c-hid: Support being a panel follower
>   HID: i2c-hid: Do panel follower work on the system_wq
>   arm64: dts: qcom: sc7180: Link trogdor touchscreens to the panels
> 
>  .../bindings/input/elan,ekth6915.yaml         |   5 +
>  .../bindings/input/goodix,gt7375p.yaml        |   5 +
>  .../bindings/input/hid-over-i2c.yaml          |   2 +
>  .../input/touchscreen/touchscreen.yaml        |   7 +
>  Documentation/gpu/todo.rst                    |  24 ++
>  .../boot/dts/qcom/sc7180-trogdor-coachz.dtsi  |   1 +
>  .../dts/qcom/sc7180-trogdor-homestar.dtsi     |   1 +
>  .../boot/dts/qcom/sc7180-trogdor-lazor.dtsi   |   1 +
>  .../boot/dts/qcom/sc7180-trogdor-pompom.dtsi  |   1 +
>  .../qcom/sc7180-trogdor-quackingstick.dtsi    |   1 +
>  .../dts/qcom/sc7180-trogdor-wormdingler.dtsi  |   1 +
>  drivers/gpu/drm/drm_panel.c                   | 218 ++++++++++-
>  drivers/hid/i2c-hid/Kconfig                   |   2 +
>  drivers/hid/i2c-hid/i2c-hid-core.c            | 349 +++++++++++++-----
>  drivers/of/property.c                         |   2 +
>  include/drm/drm_panel.h                       |  94 +++++
>  16 files changed, 617 insertions(+), 97 deletions(-)
> 
> -- 
> 2.41.0.487.g6d72f3e995-goog
>