>-----Original Message-----
>From: Grant Grundler <grundler@xxxxxxxxxxxx>
>Sent: Monday, November 26, 2018 6:28 PM
>To: Grant Grundler <grundler@xxxxxxxxxxxx>
>Cc: Ryan Lee <RyanS.Lee@xxxxxxxxxxxxxxxxxxx>; Liam Girdwood
><lgirdwood@xxxxxxxxx>; broonie@xxxxxxxxxx; perex@xxxxxxxx;
>tiwai@xxxxxxxx; Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>;
>Benson Leung <bleung@xxxxxxxxxxxx>; alsa-devel@xxxxxxxxxxxxxxxx; LKML
><linux-kernel@xxxxxxxxxxxxxxx>
>Subject: Re: [PATCH] ASoC: max98373: Added max98373_reset for stable amp
>reset
>
>EXTERNAL EMAIL
>
>
>
>I just realized I had one more question...
>
>On Mon, Nov 26, 2018 at 6:24 PM Grant Grundler <grundler@xxxxxxxxxxxx>
>wrote:
>>
>> Hi Ryan!
>>
>> Just some questions inline - in general I like the reset function.
>>
>> On Mon, Nov 26, 2018 at 10:46 AM Ryan Lee
><RyanS.Lee@xxxxxxxxxxxxxxxxxxx> wrote:
>> >
>> > Signed-off-by: Ryan Lee <ryans.lee@xxxxxxxxxxxxxxxxxxx>
>> > ---
>> > Changes : Created max98373_reset function to minimize code duplication.
>> > Changed regmap_write to regmap_update_bits. Other bits except
>LSB need to be masked.
>> > Added reset verification step to make sure software reset is
>completed well. Software reset is done in 10ms in normal case.
>> > Revision ID is available when the amp is in the idle state which means
>software reset is completed.
>
>Why not poll the RevID register a few times until it gives a value?
>
>Then structure the code to try reset twice (maybe three times).
>This would avoid the unusual "sleep time after reset is increased" code.
Let me fix unusual things here. Thanks for the comment.
>
>cheers,
>grant
>
>> > Software reset will be performed maximum 3 times to avoid amp
>reset failure. Generally it is done in the first trial.
>> > sleep time after software reset is increased + 30ms for every retrial.
>Maximum possible msleep time is 100 ms (initial 10 ms + 30 ms * 3 times).
>>
>> Why is the sleep time increased after each SW reset?
>> What is the failure case that you've seen which would benefit from this?
>>
>> >
>> > sound/soc/codecs/max98373.c | 41
>> > +++++++++++++++++++++++++++++++++++------
>> > 1 file changed, 35 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/sound/soc/codecs/max98373.c
>> > b/sound/soc/codecs/max98373.c index a09d013..55af7f02 100644
>> > --- a/sound/soc/codecs/max98373.c
>> > +++ b/sound/soc/codecs/max98373.c
>> > @@ -724,14 +724,45 @@ static struct snd_soc_dai_driver max98373_dai[]
>= {
>> > }
>> > };
>> >
>> > +static void max98373_reset(struct max98373_priv *max98373, struct
>> > +device *dev) {
>> > + int ret, reg, count, delay;
>> > +
>> > + count = 0;
>> > + while (true) {
>> > + /* Software Reset */
>> > + ret = regmap_update_bits(max98373->regmap,
>> > + MAX98373_R2000_SW_RESET,
>> > + MAX98373_SOFT_RESET,
>> > + MAX98373_SOFT_RESET);
>> > + if (ret)
>> > + dev_err(dev, "Reset command failed.
>> > + (ret:%d)\n", ret);
>> > +
>> > + delay = 10000 + (count * 30000);
>> > + usleep_range(delay, delay + 1000);
>> > +
>> > + /* Software Reset Verification */
>> > + ret = regmap_read(max98373->regmap,
>> > + MAX98373_R21FF_REV_ID, ®);
>> > + if (!ret) {
>> > + dev_info(dev, "Reset completed (retry:%d)\n", count);
>> > + break;
>>
>> Instead of break, can the code return here?
>> "break" implies something else will happen after the while loop exits
>> - there isn't.
>>
>> > + }
>> > +
>> > + if (++count > 3) {
>> > + dev_err(dev, "Reset failed. (ret:%d)\n", ret);
>> > + break;
>> > + }
>> > + usleep_range(10000, 11000);
>>
>> Why is there a second delay after reading MAX98373_R21FF_REV_ID?
>> Is this really necessary?
>>
>> If the second usleep_range() isn't needed, it would be better/clearer
>> to make code loop on "while (count < 4)". And then outside the while
>> loop, use dev_err() to share what the failure was.
>>
>> > + }
>> > +}
>> > +
>> > static int max98373_probe(struct snd_soc_component *component) {
>> > struct max98373_priv *max98373 =
>> > snd_soc_component_get_drvdata(component);
>> >
>> > /* Software Reset */
>> > - regmap_write(max98373->regmap,
>> > - MAX98373_R2000_SW_RESET, MAX98373_SOFT_RESET);
>> > - usleep_range(10000, 11000);
>> > + max98373_reset(max98373, component->dev);
>> >
>> > /* IV default slot configuration */
>> > regmap_write(max98373->regmap, @@ -818,9 +849,7 @@ static
>> > int max98373_resume(struct device *dev) {
>> > struct max98373_priv *max98373 = dev_get_drvdata(dev);
>> >
>> > - regmap_write(max98373->regmap,
>> > - MAX98373_R2000_SW_RESET, MAX98373_SOFT_RESET);
>> > - usleep_range(10000, 11000);
>> > + max98373_reset(max98373, dev);
>> > regcache_cache_only(max98373->regmap, false);
>> > regcache_sync(max98373->regmap);
>> > return 0;
>> > --
>> > 2.7.4
>> >
>>
>> cheers,
>> grant
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