[PATCH v2] ASoC: fsl_sai: Add isr to deal with error flag

[Mark Brown]

On Thu, Mar 27, 2014 at 07:06:59PM +0800, Nicolin Chen wrote:
> It's quite cricial to clear error flags because SAI might hang if getting
> FIFO underrun during playback (I haven't confirmed the same issue on Rx
> overflow though).
> 
> So this patch enables those irq and adds isr() to clear the flags so as to
> keep playback entirely safe.

So, I've applied this since we're (hopefully!) very near the merge
window opening and it seems like it should be an improvement overall.
However a few things below:

> +	/* Only handle those what we enabled */
> +	mask = (FSL_SAI_FLAGS >> FSL_SAI_CSR_xIE_SHIFT) << FSL_SAI_CSR_xF_SHIFT;

The shifting here could use a comment.

> +	regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
> +			   FSL_SAI_CSR_xF_W_MASK | FSL_SAI_CSR_FR, xcsr);

Using update_bits() is going to do an extra read, better to do this as:

	if (xcsr)
		regmap_write(sai->regmap, FSL_SAI_RCSR, xcsr);

otherwise we might be ignoring any of the bits that are actually clear
on read (it seems like there are some?).

> +	return IRQ_HANDLED;

I'd expect to see IRQ_NONE if we didn't actually see an interrupt
source.
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