linux-kernel - Re: [PATCH] ALSA: hda: runtime PM is always active

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Message-ID: <s5h7eetc2x1.wl-tiwai@suse.de>
Date:   Thu, 24 Jan 2019 19:43:06 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Sameer Pujar <spujar@...dia.com>
Cc:     <abhijeet.kumar@...el.com>, <perex@...ex.cz>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ALSA: hda: runtime PM is always active

On Thu, 24 Jan 2019 19:15:12 +0100,
Sameer Pujar wrote:
> 
> 
> On 1/24/2019 9:34 PM, Takashi Iwai wrote:
> > On Thu, 24 Jan 2019 16:57:11 +0100,
> > Sameer Pujar wrote:
> >> The runtime PM count is incremented and set to active during hda codec
> >> device init, but it is decremented and set to suspend during exit only.
> >> Hence the runtime PM status is always active and hda device cannot be
> >> put to runtime suspend. Keeping device usage active for entire period,
> >> though nothing really happening on the device, seems unnecessary.
> >>
> >> This patch avoides incrementing runtime PM usage count of the device.
> >>
> >> Signed-off-by: Sameer Pujar <spujar@...dia.com>
> >> Reviewed-by: Ravindra Lokhande <rlokhande@...dia.com>
> >> Reviewed-by: Mohan Kumar D <mkumard@...dia.com>
> > This breaks the existing things, I'm afraid.
> > Did you really test and verify the behavior...?
> >
> > The runtime PM refcount is decremented at snd_hda_codec_register(),
> > and that's the place to let runtime suspend of the codec really
> > effective.  (It's not about the controller, though.)
> >
> It worked fine at my end. I could put the device to runtime suspend
> and resume it back multiple times.
> Since you are suggesting it could break things, let me rework on the
> patch and dig up a little more to
> see if there is better way to fix this.

Well, I don't see what you want to "fix".  Do you see any bug?


thanks,

Takashi

> 
> Thanks,
> Sameer.
> 
> > thanks,
> >
> > Takashi
> >
> >
> >> ---
> >>   sound/hda/hdac_device.c | 6 ------
> >>   1 file changed, 6 deletions(-)
> >>
> >> diff --git a/sound/hda/hdac_device.c b/sound/hda/hdac_device.c
> >> index 95b073e..72aa342 100644
> >> --- a/sound/hda/hdac_device.c
> >> +++ b/sound/hda/hdac_device.c
> >> @@ -31,9 +31,6 @@ static void default_release(struct device *dev)
> >>    *
> >>    * Returns zero for success or a negative error code.
> >>    *
> >> - * This function increments the runtime PM counter and marks it active.
> >> - * The caller needs to turn it off appropriately later.
> >> - *
> >>    * The caller needs to set the device's release op properly by itself.
> >>    */
> >>   int snd_hdac_device_init(struct hdac_device *codec, struct hdac_bus *bus,
> >> @@ -55,8 +52,6 @@ int snd_hdac_device_init(struct hdac_device *codec, struct hdac_bus *bus,
> >>   	codec->bus = bus;
> >>   	codec->addr = addr;
> >>   	codec->type = HDA_DEV_CORE;
> >> -	pm_runtime_set_active(&codec->dev);
> >> -	pm_runtime_get_noresume(&codec->dev);
> >>   	atomic_set(&codec->in_pm, 0);
> >>     	err = snd_hdac_bus_add_device(bus, codec);
> >> @@ -123,7 +118,6 @@ EXPORT_SYMBOL_GPL(snd_hdac_device_init);
> >>    */
> >>   void snd_hdac_device_exit(struct hdac_device *codec)
> >>   {
> >> -	pm_runtime_put_noidle(&codec->dev);
> >>   	snd_hdac_bus_remove_device(codec->bus, codec);
> >>   	kfree(codec->vendor_name);
> >>   	kfree(codec->chip_name);
> >> -- 
> >> 2.7.4
> >>
> >>
>