linux-kernel - Re: [PATCH v2 37/66] media: sun6i-csi: Move power management to runtime pm in capture

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Message-ID: <Ygt6vwydxg9/WuDH@pendragon.ideasonboard.com>
Date:   Tue, 15 Feb 2022 12:04:47 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-staging@...ts.linux.dev,
        Yong Deng <yong.deng@...ewell.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Helen Koike <helen.koike@...labora.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 37/66] media: sun6i-csi: Move power management to
 runtime pm in capture

Hi Paul,

On Tue, Feb 15, 2022 at 10:56:22AM +0100, Paul Kocialkowski wrote:
> On Mon 14 Feb 22, 20:30, Sakari Ailus wrote:
> > On Sat, Feb 05, 2022 at 07:54:00PM +0100, Paul Kocialkowski wrote:
> > > Let's just enable the module when we start using it (at stream on)
> > > and benefit from runtime pm instead of enabling it at first open.
> > > 
> > > Also reorder the call to v4l2_pipeline_pm_get.
> > > 
> > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> > 
> > Nice patch!
> 
> Thanks!
> 
> > Do you still need v4l2_pipeline_pm_put()? Removing it would be a separate
> > patch of course.
> 
> My understanding is that this is still useful if there are drivers in the
> pipeline that rely on s_power instead of rpm (a typical case could be an
> old sensor driver). So that's why this is kept around, but all other components
> of the pipeline (isp/csi/mipi csi-2) are using rpm now.

If that's not the case on your test platforms, I think it would be
better to drop support for this old API, and convert drivers that still
use .s_power() if someone needs to use one on an Allwinner platform.

-- 
Regards,

Laurent Pinchart