linux-kernel - Re: [PATCH] ASoC: hdac_hdmi: Ensuring proper setting of output widget power state

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Date:   Fri, 12 Jan 2018 12:09:00 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Kumar, Abhijeet" <abhijeet.kumar@...el.com>
Cc:     "Koul, Vinod" <vinod.koul@...el.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        "Singh, Guneshwor O" <guneshwor.o.singh@...el.com>,
        "Kp, Jeeja" <jeeja.kp@...el.com>,
        "Tayal, SandeepX" <sandeepx.tayal@...el.com>,
        "Prusty, Subhransu S" <subhransu.s.prusty@...el.com>,
        Mark Brown <broonie@...nel.org>,
        "Jaroslav Kysela" <perex@...ex.cz>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ASoC: hdac_hdmi: Ensuring proper setting of output widget power state

On Fri, 12 Jan 2018 11:37:28 +0100,
Kumar, Abhijeet wrote:
> 
> > It's better, but doesn't guarantee that the node reached the given power state.  codec_read assures that the verb is sent and the codec gives the response.  But it means only the target state gets updated, and doesn't mean that the actual state reached.
> 
> Thanks Takashi for replying. I guess, I  should make use of return value from codec_read and retry if power state is not set properly! I'll make those changes and update again. And just wondering, how does hdmi_codec_prepare() and hdmi_codec_complete() gurantee while powering up and down the afg ?

There are two power states in the codec node: the target and the
actual.  By setting the power state, the target is set, but the actual
state change may still take some time.  In such a case, you'd need to
wait until the actual state reaches.  See hda_sync_power_state() in
the hda legacy.


Takashi