[alsa-devel] [PATCH] ASoC: nau8825: fix fake interruption when booting

[John Hsu]

There is no pull-up resistor at IRQ line where it connects from
the codec to SoC. When booting, the signal of IRQ pin will keep low
which makes the SoC invoke the ISR repeatedly because the IRQ is
registered trigger low. It will not stop until the codec sets up
the interruption and pulls the signal high. In the patch,
nau8825 will internally pull the signal to high at booting in case
the fake interrupts happen.

The patch help to fix the issue as follows:
Google issue 133904101: Cave: excessive number of interrupts before Nau8825 codec is initialized
Reported Issue
Chrome OS Version  :  ChromeOS R76-12217.0.0
Type of hardware   :

What steps will reproduce the problem?
Boot device
What is the expected output?
A lot of interrupts without any events
What do you see instead?
The fake interrupts are gone

How frequently does this problem reproduce?
Always

What is the impact to the user, and is there a workaround?
If so, what is it?

BUG=b:133904101
TEST=Boot device, and then check the interrupts are real.

Signed-off-by: John Hsu <KCHSU0 at nuvoton.com>
---
 sound/soc/codecs/nau8825.c | 4 ++++
 sound/soc/codecs/nau8825.h | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/sound/soc/codecs/nau8825.c b/sound/soc/codecs/nau8825.c
index 47e65cf99879..83ec841f7865 100644
--- a/sound/soc/codecs/nau8825.c
+++ b/sound/soc/codecs/nau8825.c
@@ -1881,6 +1881,10 @@ static void nau8825_init_regs(struct nau8825 *nau8825)
 		NAU8825_JACK_EJECT_DEBOUNCE_MASK,
 		nau8825->jack_eject_debounce << NAU8825_JACK_EJECT_DEBOUNCE_SFT);
 
+	/* Pull up IRQ pin */
+	regmap_update_bits(regmap, NAU8825_REG_INTERRUPT_MASK,
+		NAU8825_IRQ_PIN_PULLUP | NAU8825_IRQ_PIN_PULL_EN,
+		NAU8825_IRQ_PIN_PULLUP | NAU8825_IRQ_PIN_PULL_EN);
 	/* Mask unneeded IRQs: 1 - disable, 0 - enable */
 	regmap_update_bits(regmap, NAU8825_REG_INTERRUPT_MASK, 0x7ff, 0x7ff);
 
diff --git a/sound/soc/codecs/nau8825.h b/sound/soc/codecs/nau8825.h
index f6074c618569..3f41897ed3f6 100644
--- a/sound/soc/codecs/nau8825.h
+++ b/sound/soc/codecs/nau8825.h
@@ -171,6 +171,8 @@
 #define NAU8825_JACK_POLARITY	(1 << 1) /* 0 - active low, 1 - active high */
 
 /* INTERRUPT_MASK (0xf) */
+#define NAU8825_IRQ_PIN_PULLUP (1 << 14)
+#define NAU8825_IRQ_PIN_PULL_EN (1 << 13)
 #define NAU8825_IRQ_OUTPUT_EN (1 << 11)
 #define NAU8825_IRQ_HEADSET_COMPLETE_EN (1 << 10)
 #define NAU8825_IRQ_RMS_EN (1 << 8)
-- 
2.21.0