[alsa-devel] [PATCH 3/5] ASoC: dwc: Iterate over all channels

[Andrew Jackson]

On 12/04/14 06:55, rajeev kumar wrote:
> On Wed, Dec 3, 2014 at 10:59 PM, Mark Brown <broonie at kernel.org> wrote:
>> On Wed, Dec 03, 2014 at 04:39:01PM +0000, Andrew Jackson wrote:
>>
>>> +     /* Iterate over set of channels - independently controlled.
>>> +      */
>>> +     do {
>>> +             if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
>>> +                     i2s_write_reg(dev->i2s_base, TCR(ch_reg),
>>> +                                   xfer_resolution);
>>> +                     i2s_write_reg(dev->i2s_base, TFCR(ch_reg), 0x02);
>>> +                     irq = i2s_read_reg(dev->i2s_base, IMR(ch_reg));
>>> +                     i2s_write_reg(dev->i2s_base, IMR(ch_reg), irq & ~0x30);
>>> +                     i2s_write_reg(dev->i2s_base, TER(ch_reg), 1);
>>> +             } else {
>>> +                     i2s_write_reg(dev->i2s_base, RCR(ch_reg),
>>> +                                   xfer_resolution);
>>> +                     i2s_write_reg(dev->i2s_base, RFCR(ch_reg), 0x07);
>>> +                     irq = i2s_read_reg(dev->i2s_base, IMR(ch_reg));
>>> +                     i2s_write_reg(dev->i2s_base, IMR(ch_reg), irq & ~0x03);
>>> +                     i2s_write_reg(dev->i2s_base, RER(ch_reg), 1);
>>> +             }
>>> +     } while (ch_reg-- > 0);
>>
>> The normal way to write an iteration would be with a for loop - why are
>> we not doing that?
>>
>> Also I see that you've not sent these as a single thread - please use
>> --thread.
> 
> designware i2s has individual register for channel support. It is like
> TCR(0), TCR(1) and so on.. So a macro is defined to capture these
> please check below #define
> 
> #define TCR(x)      (0x40 * x + 0x034)
> 
> and the same is true for capture also. So there is no need for
> iteration. Only writing to the particular register will do the work.

However params_channels returns the number of channels that the device needs to configure.  So, for example, when there are four channels two sets of channel registers need to be programmed.


	Andrew
> 
> ~Rajeev
>