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From:   Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
To:     Brent Lu <brent.lu@intel.com>,
        "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>
CC:     Support Opensource <Support.Opensource@diasemi.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] ASoC: da7219: remove SRM lock check retry
Thread-Topic: [PATCH] ASoC: da7219: remove SRM lock check retry
Thread-Index: AQHVqaxDP6cBrmECm0aX2T25rtDQx6eoJvjg
Date:   Tue, 3 Dec 2019 09:46:03 +0000
Message-ID: <AM5PR1001MB0994EB497D3BC7D0F4C6FD9080420@AM5PR1001MB0994.EURPRD10.PROD.OUTLOOK.COM>
References: <1575358265-17905-1-git-send-email-brent.lu@intel.com>
In-Reply-To: <1575358265-17905-1-git-send-email-brent.lu@intel.com>
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On 03 December 2019 07:31, Brent Lu wrote:

> For platforms not able to provide WCLK in the PREPARED runtime state, it
> takes 400ms for codec driver to print the message "SRM failed to lock" in
> the da7219_dai_event() function which is called when DAPM widgets are
> powering up. The latency penalty to audio input/output is too much so the
> retry (8 times) and delay (50ms each retry) are removed.
>=20
> Another reason is current Cold output latency requirement in Android CDD =
is
> 500ms but will be reduced to 200ms for 2021 platforms. With the 400ms
> latency it would be difficult to pass the Android CTS test.

We can potentially reduce the timings here for something shorter although I=
'd
need to speak with the HW team as to what, if any reduction is feasible. Ho=
wever
this is not a real fix as there's potential for audible noises when you don=
't
enable WCLK first. As far as I can tell the Intel platforms are capable of
enabling clocks early, as can be seen in this board file with early SCLK en=
able:

https://elixir.bootlin.com/linux/latest/source/sound/soc/intel/boards/kbl_r=
t5663_max98927.c#L99

I think there's a need to find some method to enable the WCLK signal otherw=
ise
there's the potential for audible artefacts when SRM finally locks which is=
 not
going to be pleasant.

>=20
> Signed-off-by: Brent Lu <brent.lu@intel.com>
> ---
>  sound/soc/codecs/da7219.c | 3 ++-
>  sound/soc/codecs/da7219.h | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>=20
> diff --git a/sound/soc/codecs/da7219.c b/sound/soc/codecs/da7219.c
> index f83a6ea..042e701 100644
> --- a/sound/soc/codecs/da7219.c
> +++ b/sound/soc/codecs/da7219.c
> @@ -833,7 +833,8 @@ static int da7219_dai_event(struct snd_soc_dapm_widge=
t
> *w,
>  				srm_lock =3D true;
>  			} else {
>  				++i;
> -				msleep(50);
> +				if (i < DA7219_SRM_CHECK_RETRIES)
> +					msleep(50);
>  			}
>  		} while ((i < DA7219_SRM_CHECK_RETRIES) && (!srm_lock));
>=20
> diff --git a/sound/soc/codecs/da7219.h b/sound/soc/codecs/da7219.h
> index 88b67fe..3149986 100644
> --- a/sound/soc/codecs/da7219.h
> +++ b/sound/soc/codecs/da7219.h
> @@ -770,7 +770,7 @@
>  #define DA7219_PLL_INDIV_36_TO_54_MHZ_VAL	16
>=20
>  /* SRM */
> -#define DA7219_SRM_CHECK_RETRIES	8
> +#define DA7219_SRM_CHECK_RETRIES	1
>=20
>  /* System Controller */
>  #define DA7219_SYS_STAT_CHECK_RETRIES	6
> --
> 2.7.4