Paul Cercueil paul@crapouillou.net writes:
Hi Aidan,
Le mer., juil. 20 2022 at 15:43:06 +0100, Aidan MacDonald aidanmacdonald.0x0@gmail.com a écrit :
Paul Cercueil paul@crapouillou.net writes:
According to the JZ4740 programming manual JZ_AIC_CTRL_FLUSH flushes both FIFOs, so it's not equivalent JZ4760_AIC_CTRL_TFLUSH. I don't think it's a good idea to confuse the two, or we'd need comments to explain why JZ4740 uses TFLUSH but not RFLUSH.
"shared_fifo_flush" is pretty much self-explanatory though. It then becomes obvious looking at the code that when this flag is set, TFLUSH flushes both FIFOs.
If you prefer... you can #define JZ_AIC_CTRL_FLUSH JZ_AIC_CTRL_TFLUSH. I don't like the JZ4760 prefix, this is in no way specific to the JZ4760.
Makes sense, I'll stick with TFLUSH / RFLUSH only.
#define JZ_AIC_CTRL_OUTPUT_SAMPLE_SIZE_OFFSET 19 #define JZ_AIC_CTRL_INPUT_SAMPLE_SIZE_OFFSET 16 @@ -90,6 +93,8 @@ enum jz47xx_i2s_version { struct i2s_soc_info { enum jz47xx_i2s_version version; struct snd_soc_dai_driver *dai;
- bool shared_fifo_flush;
}; struct jz4740_i2s { @@ -124,12 +129,33 @@ static int jz4740_i2s_startup(struct snd_pcm_substream *substream, uint32_t conf, ctrl; int ret;
- /*
* When we can flush FIFOs independently, only flush the* FIFO that is starting up.*/- if (!i2s->soc_info->shared_fifo_flush) {
ctrl = jz4740_i2s_read(i2s, JZ_REG_AIC_CTRL);if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)ctrl |= JZ4760_AIC_CTRL_TFLUSH;elsectrl |= JZ4760_AIC_CTRL_RFLUSH;jz4740_i2s_write(i2s, JZ_REG_AIC_CTRL, ctrl);- }
Wouldn't it be simpler to do one single if/else? And hy is one checked before the (snd_soc_dai_active(dai)) check, and the other is checked after?
snd_soc_dai_active() is essentially checking if there's an active substream. Eg. if no streams are open and you start playback, then the DAI will be inactive. If you then start capture while playback is running, the DAI is already active. With a shared flush bit we can only flush if there are no other active substreams (because we don't want to disturb the active stream by flushing the FIFO) so it goes after the snd_soc_dai_active() check. When the FIFOs can be separately flushed, flushing can be done before the check because it won't disturb any active substream.
Ok. It makes sense then. Please add some info about this in the commit message, because it really wasn't obvious to me.
It wasn't that obvious to me either :)
I've added code comments too since it seems likely to trip people up if you're only taking a casual glance.
You should maybe factorize the read-modify-write into its own function. I know this gets eventually modified by [03/11], but this [01/11] is a bugfix so it will be applied to older kernels, and I'd rather not have duplicated code there.
Cheers, -Paul
And I've factored out the r-m-w helper as requested.
Regards, Aidan