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From: Johan Hovold <johan@kernel.org>
To: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Dmitry Osipenko <digetx@gmail.com>,
	devel@driverdev.osuosl.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linuxarm@huawei.com, Jonathan Hunter <jonathanh@nvidia.com>,
	linux-tegra@vger.kernel.org,
	Thierry Reding <thierry.reding@gmail.com>,
	mauro.chehab@huawei.com,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org
Subject: Re: [PATCH 17/78] staging: media: vde: use pm_runtime_resume_and_get()
Date: Tue, 27 Apr 2021 14:34:56 +0200	[thread overview]
Message-ID: <YIgE8PfASn6nua5B@hovoldconsulting.com> (raw)
In-Reply-To: <20210427112250.5d40c4f4@coco.lan>

On Tue, Apr 27, 2021 at 11:22:50AM +0200, Mauro Carvalho Chehab wrote:
> Hi Dmitry,
> 
> Em Sat, 24 Apr 2021 10:35:22 +0300
> Dmitry Osipenko <digetx@gmail.com> escreveu:
> 
> > 24.04.2021 09:44, Mauro Carvalho Chehab пишет:
> > > Commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> > > added pm_runtime_resume_and_get() in order to automatically handle
> > > dev->power.usage_count decrement on errors.
> > > 
> > > Use the new API, in order to cleanup the error check logic.
> > > 
> > > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> > > ---
> > >  drivers/staging/media/tegra-vde/vde.c | 16 ++++++++++------
> > >  1 file changed, 10 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/staging/media/tegra-vde/vde.c b/drivers/staging/media/tegra-vde/vde.c
> > > index 28845b5bafaf..8936f140a246 100644
> > > --- a/drivers/staging/media/tegra-vde/vde.c
> > > +++ b/drivers/staging/media/tegra-vde/vde.c
> > > @@ -775,9 +775,9 @@ static int tegra_vde_ioctl_decode_h264(struct tegra_vde *vde,
> > >  	if (ret)
> > >  		goto release_dpb_frames;
> > >  
> > > -	ret = pm_runtime_get_sync(dev);
> > > +	ret = pm_runtime_resume_and_get(dev);
> > >  	if (ret < 0)
> > > -		goto put_runtime_pm;
> > > +		goto unlock;
> > >  
> > >  	/*
> > >  	 * We rely on the VDE registers reset value, otherwise VDE
> > > @@ -843,6 +843,8 @@ static int tegra_vde_ioctl_decode_h264(struct tegra_vde *vde,
> > >  put_runtime_pm:
> > >  	pm_runtime_mark_last_busy(dev);
> > >  	pm_runtime_put_autosuspend(dev);
> > > +
> > > +unlock:
> > >  	mutex_unlock(&vde->lock);
> > >  
> > >  release_dpb_frames:
> > > @@ -1069,8 +1071,8 @@ static int tegra_vde_probe(struct platform_device *pdev)
> > >  	 * power-cycle it in order to put hardware into a predictable lower
> > >  	 * power state.
> > >  	 */
> > > -	pm_runtime_get_sync(dev);
> > > -	pm_runtime_put(dev);
> > > +	if (pm_runtime_resume_and_get(dev) >= 0)
> > > +		pm_runtime_put(dev);
> > >  
> > >  	return 0;
> > >  
> > > @@ -1088,8 +1090,9 @@ static int tegra_vde_remove(struct platform_device *pdev)
> > >  {
> > >  	struct tegra_vde *vde = platform_get_drvdata(pdev);
> > >  	struct device *dev = &pdev->dev;
> > > +	int ret;
> > >  
> > > -	pm_runtime_get_sync(dev);
> > > +	ret = pm_runtime_resume_and_get(dev);
> > >  	pm_runtime_dont_use_autosuspend(dev);
> > >  	pm_runtime_disable(dev);
> > >  
> > > @@ -1097,7 +1100,8 @@ static int tegra_vde_remove(struct platform_device *pdev)
> > >  	 * Balance RPM state, the VDE power domain is left ON and hardware
> > >  	 * is clock-gated. It's safe to reboot machine now.
> > >  	 */
> > > -	pm_runtime_put_noidle(dev);
> > > +	if (ret >= 0)
> > > +		pm_runtime_put_noidle(dev);
> > >  	clk_disable_unprepare(vde->clk);
> > >  
> > >  	misc_deregister(&vde->miscdev);
> > >   
> > 
> > Hello Mauro,
> > 
> > Thank you very much for the patch. It looks to me that the original
> > variant was a bit simpler, this patch adds more code lines without
> > changing the previous behaviour. Or am I missing something?

I agree, the above does not look like an improvement at all.

> While on several places the newer code is simpler, the end goal here is
> to replace all occurrences of pm_runtime_get_sync() from the media 
> subsystem, due to the number of problems we're having with this:
> 
> 1. despite its name, this is actually a PM runtime resume call,
>    but some developers didn't seem to realize that, as I got this
>    pattern on some drivers:
> 
>         pm_runtime_get_sync(&client->dev);
>         pm_runtime_disable(&client->dev);
>         pm_runtime_set_suspended(&client->dev);
>         pm_runtime_put_noidle(&client->dev);
> 
>    It makes no sense to resume PM just to suspend it again ;-)

It very well may. You're resuming the device and leaving it a defined
power state before balancing the PM count, cleaning up and unbinding the
driver.

>    The name of the new variant is a lot clearer:
> 	pm_runtime_resume_and_get()

For people not used to the API perhaps.

> 2. Usual *_get() methods only increment their use count on success,
>    but pm_runtime_get_sync() increments it unconditionally. Due to
>    that, several drivers were mistakenly not calling
>    pm_runtime_put_noidle() when it fails;

As I mentioned elsewhere, all pm_runtime_get calls increment the usage
count so the API is consistent.
 
> 3. Consistency: we did similar changes subsystem wide with
>    for instance strlcpy() and strcpy() that got replaced by
>    strscpy(). Having all drivers using the same known-to-be-safe
>    methods is a good thing;

There's no know-to-be safe API. People will find ways to get this wrong
too.

And the old interface isn't going away from the kernel even if you
manage to not use it in media.

> 4. Prevent newer drivers to copy-and-paste a code that it would
>    be easier to break if they don't truly understand what's behind
>    the scenes.

Johan

  reply	other threads:[~2021-04-27 12:34 UTC|newest]

Thread overview: 127+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-24  6:44 [PATCH 00/78] media: use pm_runtime_resume_and_get() instead of pm_runtime_get_sync() Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 01/78] media: atmel: properly get pm_runtime Mauro Carvalho Chehab
2021-04-24  9:36   ` kernel test robot
2021-04-24  6:44 ` [PATCH 02/78] media: marvel-ccic: fix some issues when getting pm_runtime Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 03/78] media: mdk-mdp: fix pm_runtime_get_sync() usage count Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 04/78] media: rcar_fdp1: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 05/78] media: mdk-mdp: " Mauro Carvalho Chehab
2021-04-24 18:23   ` Ezequiel Garcia
2021-04-24  6:44 ` [PATCH 06/78] media: renesas-ceu: " Mauro Carvalho Chehab
2021-04-24  8:11   ` Jacopo Mondi
2021-04-24  6:44 ` [PATCH 07/78] media: s5p: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 08/78] media: am437x:: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 09/78] media: sh_vou: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 10/78] media: sti/hva: use pm_runtime_resume_and_get() Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 11/78] staging: media: rkvdec: fix pm_runtime_get_sync() usage count Mauro Carvalho Chehab
2021-04-24 23:20   ` Ezequiel Garcia
2021-04-24  6:44 ` [PATCH 12/78] staging: media: atomisp_fops: use pm_runtime_resume_and_get() Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 13/78] staging: media: hantro_drv: " Mauro Carvalho Chehab
2021-04-24 23:23   ` Ezequiel Garcia
2021-04-26 12:33     ` Mauro Carvalho Chehab
2021-04-26 12:42       ` Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 14/78] staging: media: imx7-mipi-csis: " Mauro Carvalho Chehab
2021-04-26 10:11   ` Rui Miguel Silva
2021-04-24  6:44 ` [PATCH 15/78] staging: media: ipu3: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 16/78] staging: media: cedrus_video: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 17/78] staging: media: vde: " Mauro Carvalho Chehab
2021-04-24  7:35   ` Dmitry Osipenko
2021-04-27  9:22     ` Mauro Carvalho Chehab
2021-04-27 12:34       ` Johan Hovold [this message]
2021-04-24  6:44 ` [PATCH 18/78] staging: media: csi: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 19/78] staging: media: vi: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 20/78] media: mtk-vcodec: fix pm_runtime_get_sync() usage count Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 21/78] media: s5p-jpeg: " Mauro Carvalho Chehab
2021-04-27  9:14   ` Sylwester Nawrocki
2021-04-24  6:44 ` [PATCH 22/78] media: delta-v4l2: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 23/78] media: sun8i_rotate: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 24/78] media: i2c: ak7375: use pm_runtime_resume_and_get() Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 25/78] media: i2c: ccs-core: " Mauro Carvalho Chehab
2021-04-25 18:55   ` Sakari Ailus
2021-04-26 14:01     ` Mauro Carvalho Chehab
2021-04-26 14:09       ` Sakari Ailus
2021-04-26 14:16         ` Mauro Carvalho Chehab
2021-04-26 14:29           ` Sakari Ailus
2021-04-26 17:32             ` Mauro Carvalho Chehab
2021-04-27  7:02               ` Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 26/78] media: i2c: dw9714: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 27/78] media: i2c: dw9768: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 28/78] media: i2c: dw9807-vcm: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 29/78] media: i2c: hi556: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 30/78] media: i2c: imx214: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 31/78] media: i2c: imx219: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 32/78] media: i2c: imx258: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 33/78] media: i2c: imx274: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 34/78] media: i2c: imx290: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 35/78] media: i2c: imx319: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 36/78] media: i2c: imx334: " Mauro Carvalho Chehab
2021-04-26  9:06   ` Alessandrelli, Daniele
2021-04-24  6:44 ` [PATCH 37/78] media: i2c: imx355: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 38/78] media: i2c: mt9m001: " Mauro Carvalho Chehab
2021-04-24  8:24   ` Jacopo Mondi
2021-04-24 10:00     ` Johan Hovold
2021-04-26 14:38       ` Mauro Carvalho Chehab
2021-04-27 12:23         ` Johan Hovold
2021-04-28  8:31           ` Mauro Carvalho Chehab
2021-04-28 10:05             ` Johan Hovold
2021-04-28 11:28               ` Mauro Carvalho Chehab
2021-04-28 11:56                 ` Johan Hovold
2021-04-24  6:44 ` [PATCH 39/78] media: i2c: ov02a10: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 40/78] media: i2c: ov13858: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 41/78] media: i2c: ov2659: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 42/78] media: i2c: ov2685: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 43/78] media: i2c: ov2740: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 44/78] media: i2c: ov5647: " Mauro Carvalho Chehab
2021-04-24  8:30   ` Jacopo Mondi
2021-04-24  6:44 ` [PATCH 45/78] media: i2c: ov5648: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 46/78] media: i2c: ov5670: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 47/78] media: i2c: ov5675: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 48/78] media: i2c: ov5695: " Mauro Carvalho Chehab
2021-04-24  6:44 ` [PATCH 49/78] media: i2c: ov7740: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 50/78] media: i2c: ov8856: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 51/78] media: i2c: ov8865: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 52/78] media: i2c: ov9734: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 53/78] media: i2c: tvp5150: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 54/78] media: i2c: video-i2c: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 55/78] media: ipu3: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 56/78] media: coda: " Mauro Carvalho Chehab
2021-04-26  6:53   ` Philipp Zabel
2021-04-24  6:45 ` [PATCH 57/78] media: exynos4-is: " Mauro Carvalho Chehab
2021-04-25 20:57   ` Sylwester Nawrocki
2021-04-26 13:12     ` Mauro Carvalho Chehab
2021-04-27  8:06       ` Sylwester Nawrocki
2021-04-24  6:45 ` [PATCH 58/78] media: exynos-gsc: " Mauro Carvalho Chehab
2021-04-27  8:18   ` Sylwester Nawrocki
2021-04-27  9:30     ` Mauro Carvalho Chehab
2021-04-27  9:42       ` Mauro Carvalho Chehab
2021-04-27 11:50         ` Sylwester Nawrocki
2021-04-28  7:13           ` Mauro Carvalho Chehab
2021-04-28  7:17             ` Mauro Carvalho Chehab
2021-04-28  8:27               ` Sylwester Nawrocki
2021-04-24  6:45 ` [PATCH 59/78] media: mtk-jpeg: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 60/78] media: camss-csid: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 61/78] media: camss-csiphy: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 62/78] media: camss-ispif: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 63/78] media: camss-vfe: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 64/78] media: core: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 65/78] media: pm_helpers: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 66/78] media: vdec: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 67/78] media: venc: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 68/78] media: rcar-fcp: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 69/78] media: rcar-vin: " Mauro Carvalho Chehab
2021-04-24  8:33   ` Niklas Söderlund
2021-04-24  9:12   ` Geert Uytterhoeven
2021-04-26 13:33     ` Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 70/78] media: rga-buf: " Mauro Carvalho Chehab
2021-04-28 17:09   ` Ezequiel Garcia
2021-04-24  6:45 ` [PATCH 71/78] media: rkisp1-capture: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 72/78] media: s3c-camif: " Mauro Carvalho Chehab
2021-04-25 19:36   ` Sylwester Nawrocki
2021-04-24  6:45 ` [PATCH 73/78] media: s5p-mfc: " Mauro Carvalho Chehab
2021-04-27  9:36   ` Sylwester Nawrocki
2021-04-24  6:45 ` [PATCH 74/78] media: bdisp-v4l2: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 75/78] media: stm32: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 76/78] media: sun4i_v4l2: " Mauro Carvalho Chehab
2021-04-24 10:21   ` kernel test robot
2021-04-24  6:45 ` [PATCH 77/78] media: ti-vpe: " Mauro Carvalho Chehab
2021-04-24  6:45 ` [PATCH 78/78] media: vsp1: " Mauro Carvalho Chehab
2021-04-28 10:13 ` [PATCH 00/78] media: use pm_runtime_resume_and_get() instead of pm_runtime_get_sync() Dan Carpenter

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