Re: [alsa-devel] [PATCH] ASoC: max98373: Added max98373_reset for stable amp reset

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@maximintegrated.com wrote:

Signed-off-by: Ryan Lee ryans.lee@maximintegrated.com

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?

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, &reg);
  

•           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