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Message-ID: <eKiIqOeH_0iCJ5qKedzwefk36VAe-8YPqi7kG52SsMs2OxEt4u1sEML07P0RQkgNR4cuj97VduO_Xa6ktp4m2pdunmQnK8hE9Zp7dDTtruw=@emersion.fr>
Date: Thu, 18 Nov 2021 08:34:15 +0000
From: Simon Ser <contact@...rsion.fr>
To: Brian Norris <briannorris@...omium.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
Rob Clark <robdclark@...omium.org>,
David Airlie <airlied@...ux.ie>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
Doug Anderson <dianders@...omium.org>,
linux-rockchip@...ts.infradead.org,
"Kristian H . Kristensen" <hoegsberg@...gle.com>,
Andrzej Hajda <andrzej.hajda@...el.com>,
linux-input@...r.kernel.org, Pekka Paalanen <ppaalanen@...il.com>
Subject: Re: [PATCH v2 0/2] drm: Support input-boosted panel self-refresh exit
Hi,
>From a user-space point-of-view, we discussed about this patch on IRC a few
days ago [1]. Since this adds a policy decision we think it'd be best to allow
user-space to control this behavior.
Also cc Pekka.
Thanks,
Simon
[1]: https://oftc.irclog.whitequark.org/dri-devel/2021-11-07#1636276286-1636273745;
> A variety of applications have found it useful to listen to
> user-initiated input events to make decisions within a DRM driver, given
> that input events are often the first sign that we're going to start
> doing latency-sensitive activities:
>
> * Panel self-refresh: software-directed self-refresh (e.g., with
> Rockchip eDP) is especially latency sensitive. In some cases, it can
> take 10s of milliseconds for a panel to exit self-refresh, which can
> be noticeable. Rockchip RK3399 Chrome OS systems have always shipped
> with an input_handler boost, that preemptively exits self-refresh
> whenever there is input activity.
>
> * GPU drivers: on GPU-accelerated desktop systems, we may need to
> render new frames immediately after user activity. Powering up the
> GPU can take enough time that it is worthwhile to start this process
> as soon as there is input activity. Many Chrome OS systems also ship
> with an input_handler boost that powers up the GPU.
>
> I implement the first bullet in this series, and I also compared with
> some out-of-tree patches for the second, to ensure this could be useful
> there too.
>
> Past work on upstreaming a variety of Chromebook display patches got
> held up for this particular feature, as there was some desire to make it
> a bit more generic, for one. See the latest here:
>
> https://lore.kernel.org/all/20180405095000.9756-25-enric.balletbo@collabora.com/
> [PATCH v6 24/30] drm/rockchip: Disable PSR on input events
>
> I significantly rewrote this to adapt it to the new common
> drm_self_refresh_helpers and to add a new drm_input_helper thin library,
> so I only carry my own authorship on this series.
>
> Admittedly, this "drm_input_helper" library is barely DRM-specific at
> all, except that all display- and GPU-related input-watchers are likely
> to want to watch similar device behavior (unlike, say, rfkill or led
> input_handler code). The approximate consensus so far seems to be that
> (a) this isn't much code; if we need it for other subsystems (like,
> cpufreq-boost), it's easy to implement similar logic
> (b) input subsystem maintainers think the existing input_handler
> abstraction is good enough
> So, I keep the thin input helper in drivers/gpu/drm/.
>
> v1: https://lore.kernel.org/all/20211103234018.4009771-1-briannorris@chromium.org/
>
> Changes in v2:
> - Honor CONFIG_INPUT dependency, via new CONFIG_DRM_INPUT_HELPER
> - Remove void*; users should use container_of()
> - Document the callback context
> - Delay PSR re-entry, when already disabled
> - Allow default configuration via Kconfig and modparam
> - really CC dri-devel@...ts.freedesktop.org (oops!)
>
> Brian Norris (2):
> drm/input_helper: Add new input-handling helper
> drm/self_refresh: Disable self-refresh on input events
>
> drivers/gpu/drm/Kconfig | 22 ++++
> drivers/gpu/drm/Makefile | 2 +
> drivers/gpu/drm/drm_input_helper.c | 143 ++++++++++++++++++++++
> drivers/gpu/drm/drm_self_refresh_helper.c | 98 ++++++++++++---
> include/drm/drm_input_helper.h | 41 +++++++
> 5 files changed, 292 insertions(+), 14 deletions(-)
> create mode 100644 drivers/gpu/drm/drm_input_helper.c
> create mode 100644 include/drm/drm_input_helper.h
>
> --
> 2.34.0.rc1.387.gb447b232ab-goog
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