Re: [PATCH v3 14/17] media: i2c: imx290: Initialize runtime PM before subdev

From: Guenter Roeck <linux@roeck-us.net>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: linux-media@vger.kernel.org, Sakari Ailus <sakari.ailus@iki.fi>,
	Manivannan Sadhasivam <mani@kernel.org>,
	Alexander Stein <alexander.stein@ew.tq-group.com>,
	Dave Stevenson <dave.stevenson@raspberrypi.com>,
	regressions@lists.linux.dev
Subject: Re: [PATCH v3 14/17] media: i2c: imx290: Initialize runtime PM before subdev
Date: Mon, 27 Feb 2023 09:52:45 -0800	[thread overview]
Message-ID: <20230227175245.GA3728693@roeck-us.net> (raw)
In-Reply-To: <20230116144454.1012-15-laurent.pinchart@ideasonboard.com>

Hi,

On Mon, Jan 16, 2023 at 04:44:51PM +0200, Laurent Pinchart wrote:
> Initializing the subdev before runtime PM means that no subdev
> initialization can interact with the runtime PM framework. This can be
> problematic when modifying controls, as the .s_ctrl() handler commonly
> calls pm_runtime_get_if_in_use(). These code paths are not trivial,
> making the driver fragile and possibly causing subtle bugs.
> 
> To make the subdev initialization more robust, initialize runtime PM
> first.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Acked-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> ---

This patch results in

Error log:
<stdin>:1517:2: warning: #warning syscall clone3 not implemented [-Wcpp]
drivers/media/i2c/imx290.c:1090:12: error: 'imx290_runtime_suspend' defined but not used [-Werror=unused-function]
 1090 | static int imx290_runtime_suspend(struct device *dev)
      |            ^~~~~~~~~~~~~~~~~~~~~~
drivers/media/i2c/imx290.c:1082:12: error: 'imx290_runtime_resume' defined but not used [-Werror=unused-function]
 1082 | static int imx290_runtime_resume(struct device *dev)

if PM runtime support is disabled( alpha:allmodconfig, csky:allmodconfig,
and others).

Guenter

---
#regzbot ^introduced 02852c01f6540
#regzbot title Build error in drivers/media/i2c/imx290.c if PM support is disabled

---
# bad: [f3a2439f20d918930cc4ae8f76fe1c1afd26958f] Merge tag 'rproc-v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/remoteproc/linux
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# bad: [27e45f2e59c9db2c83ed67775e911c8a3c776db2] media: ti: omap4iss: Use media_pipeline_for_each_entity()
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# good: [10591fe63691bd8199d5e7244029cc065959ffc9] media: i2c: imx290: Rename, extend and expand usage of imx290_pixfmt
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# bad: [e14d3ac81bd2264edc76bf5796305b2dfea44487] media: i2c: Add driver for OmniVision OV8858
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# bad: [7d399658f7c666ead4bc3dbe88944bb8ea7746ca] media: i2c: imx290: Configure data lanes at start time
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# bad: [02852c01f65402e2fe4a8a5fe5a0b641f245b529] media: i2c: imx290: Initialize runtime PM before subdev
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# good: [a8c3e0c1bf1e97b5ee094951ed0f1e57e3b378c7] media: i2c: imx290: Use runtime PM autosuspend
git bisect good a8c3e0c1bf1e97b5ee094951ed0f1e57e3b378c7
# first bad commit: [02852c01f65402e2fe4a8a5fe5a0b641f245b529] media: i2c: imx290: Initialize runtime PM before subdev