Mt7620 ASOC driver issue

For Developers
1

Dear developers

I'm trying to fix a issue with mt7620 I2S audio, and will be very nice if you could help in such effort.

Basically when playing a 1KHz tone using aplay command, the audio starts crackling every time I wrote to the squash file system. It's easy to test, enough running echo "hello" > /some_file at the same time that aplay 1KHztone.wav. BTW I'm using different mt76x8 boards.

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I've started checking 0048-asoc-add-mt7620-support.patch, but it will be nice if you could help me to debug further such problem.

Thank you!

2

Just for testing, what happens if you bump CONFIG_HZ to 1000?

3

Thank you for your answer. What I've done..
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but I'm afraid that it doesn't help. Same results in audio

Just for reference, same test with an old AR9331 board works nicely in openwrt 14.07 (even with CONFIG_HZ=100)
My feeling is that something is wrong with I2S dma. I'm struggling how to prioritise I2S over the rest of dma tasks

4

Hi all
FYI I've enabled I2S interrupts and the problem is gone. No audio drops at all, board works nicelly reproducing audio with aplay, madplay or mpd

--- a/target/linux/ramips/patches-4.14/0048-asoc-add-mt7620-support.patch
+++ b/target/linux/ramips/patches-4.14/0048-asoc-add-mt7620-support.patch
@@ -196,7 +196,7 @@ Signed-off-by: John Crispin <blogic@openwrt.org>
 +#define RALINK_FLAGS_ENDIAN   BIT(3)
 +#define RALINK_FLAGS_24BIT    BIT(4)
 +
-+#define RALINK_I2S_INT_EN     0
++#define RALINK_I2S_INT_EN     1
 +
 +struct ralink_i2s_stats {
 +      u32 dmafault;

but now CPU is very busy serving I2S interrupt (CPU: usr increases from 14% to 80%). Somebody that can help with this or address me on the right way in order to fix it?