From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pascal Huerst <pascal.huerst@gmail.com>
Subject: ASoC: cs4271: init/timing problem
Date: Tue, 31 Mar 2015 10:50:17 +0200
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Cc: alsa-devel@alsa-project.org, Mark Brown <broonie@kernel.org>, Paul.Handrigan@cirrus.com
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Hey all,

We have a custom built hw, based on am335x and from time to time we need
to rmmod/modprobe the ASoC machine driver. Depending on the hw, the
first call to regmap_update_bits(..) in cs4271_codec_probe(..) fails
with -EREMOTEIO.

The error is originated in:

drivers/i2c/busses/i2c-omap.c

and happens if no i2c package acknowledge is received by the host.

I think this is a timing issue and on some devices, the codec is just
not ready yet, for communication.

What is the right way to fix that? My attempt would be something like this:

const int retries = 5;

while (retries) {
	ret = regmap_update_bits(cs4271->regmap, CS4271_MODE2,
                                 CS4271_MODE2_PDN | CS4271_MODE2_CPEN,
                                 CS4271_MODE2_PDN | CS4271_MODE2_CPEN);

        if (ret == -EREMOTEIO) {
                retries--;
                udelay(1);
                continue;

        } else if (ret)
                return ret;

        break;
}

But I might also just add a proper delay before the first call to
regmap_update_bits(..)

So what is the proper way to handle this?

Thanks
Pascal