Grant,
Thanks for your feedback. Please find my answers inline.
>-----Original Message-----
>From: Grant Grundler <grundler@xxxxxxxxxxxx>
>Sent: Monday, November 26, 2018 6:25 PM
>To: Ryan Lee <RyanS.Lee@xxxxxxxxxxxxxxxxxxx>
>Cc: Liam Girdwood <lgirdwood@xxxxxxxxx>; broonie@xxxxxxxxxx;
>perex@xxxxxxxx; tiwai@xxxxxxxx; Grant Grundler
><grundler@xxxxxxxxxxxx>; 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
>
>
>
>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.
>> 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?
Generally 10ms is enough time for amp software reset but I wanted to add more guard time for the retrial because it is already failed once.
I have not seen a failure issue with 10ms delay on my test setup but I wanted to make it more conservative.
Let me remove 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.
Okay. I will fix it. Thanks for the comment.
>
>> + }
>> +
>> + 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?
It is not very necessary. I just wanted to make it more conservative because this delay is applied only when reset is failed.
>
>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.
OK. Let me fix it.
>
>> + }
>> +}
>> +
>> 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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