[alsa-devel] [PATCH] ASoC: codecs/wm8978: Only reconfigure GPIO1 when used for PLL output

[Eric Millbrandt]

Mark,

On 2012-11-13 Mark Brown wrote:

>> -            snd_soc_update_bits(codec, WM8978_GPIO_CONTROL, 0x30,
>> +            /*
>> +             * GPIO1 is used for OPCLK, reconfigure into default
>> +             * mode as input - before configuring OPCLKDIV and PLL
>> +             */
>> +            snd_soc_update_bits(codec, WM8978_GPIO_CONTROL, 0x37,
>>                                  (opclk_div - 1) << 4);
>
> Previously we weren't changing the pin mode at all, we were only
> updating the bitfield that contains OPCLK.  With your change we will
> also change the pin mode to input, but if the pin is doing any form of
> output (or anything other than input mode) I'd expect this to at least
> glitch things which seems actively harmful.  Why is it being set up as
> an input?  Though I have to say that all this handling of the pin in the
> existing driver looks at best odd.
>
> Your changelog describes what you're doing but not what is being
> fixed...

The issue was in the following snippet:

@@ -529,9 +533,6 @@ static int wm8978_configure_pll(struct snd_soc_codec *codec)
                        return idx;

                wm8978->mclk_idx = idx;
-
-               /* GPIO1 into default mode as input - before configuring PLL */
-               snd_soc_update_bits(codec, WM8978_GPIO_CONTROL, 7, 0);
        } else {
                return -EINVAL;
        }

This bit of code was always reconfiguring the pin to input when it was known
that OPCLK was not needed.  I am using GPIO1 to enable an amplifier, so I do
not want it reconfigured.  I moved the reconfiguring of GPIO1 to the block of
code under "if (f_opclk)", so we can safely assume that that pin is not being
used for something else.

However, I agree that the handling of the pin is odd.  Does OPCLK really need
to be reconfigured as input whenever the PLL values are updated?  I didn't
see anything in the user manual to suggest that that needed to be done.

Eric



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