2020-02-06 10:13:39

by Viswanath L

Subject: [PATCH] ALSA: hda: Clear RIRB status before reading WP

From: Mohan Kumar <[email protected]>

RIRB interrupt status getting cleared after the write pointer is read
causes a race condition, where last response(s) into RIRB may remain
unserviced by IRQ, eventually causing azx_rirb_get_response to fall
back to polling mode. Clearing the RIRB interrupt status ahead of
write pointer access ensures that this condition is avoided.

Signed-off-by: Mohan Kumar <[email protected]>
Signed-off-by: Viswanath L <[email protected]>
---
sound/pci/hda/hda_controller.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/sound/pci/hda/hda_controller.c b/sound/pci/hda/hda_controller.c
index 9757667..2609e39 100644
--- a/sound/pci/hda/hda_controller.c
+++ b/sound/pci/hda/hda_controller.c
@@ -1110,16 +1110,23 @@ irqreturn_t azx_interrupt(int irq, void *dev_id)
if (snd_hdac_bus_handle_stream_irq(bus, status, stream_update))
active = true;

- /* clear rirb int */
status = azx_readb(chip, RIRBSTS);
if (status & RIRB_INT_MASK) {
+ /*
+ * Clearing the interrupt status here ensures that no
+ * interrupt gets masked after the RIRB wp is read in
+ * snd_hdac_bus_update_rirb. This avoids a possible
+ * race condition where codec response in RIRB may
+ * remain unserviced by IRQ, eventually falling back
+ * to polling mode in azx_rirb_get_response.
+ */
+ azx_writeb(chip, RIRBSTS, RIRB_INT_MASK);
active = true;
if (status & RIRB_INT_RESPONSE) {
if (chip->driver_caps & AZX_DCAPS_CTX_WORKAROUND)
udelay(80);
snd_hdac_bus_update_rirb(bus);
}
- azx_writeb(chip, RIRBSTS, RIRB_INT_MASK);
}
} while (active && ++repeat < 10);

--
2.7.4

2020-02-06 12:25:13

by Takashi Iwai

Subject: Re: [PATCH] ALSA: hda: Clear RIRB status before reading WP

On Thu, 06 Feb 2020 11:10:53 +0100,
Viswanath L wrote:
>
> From: Mohan Kumar <[email protected]>
>
> RIRB interrupt status getting cleared after the write pointer is read
> causes a race condition, where last response(s) into RIRB may remain
> unserviced by IRQ, eventually causing azx_rirb_get_response to fall
> back to polling mode. Clearing the RIRB interrupt status ahead of
> write pointer access ensures that this condition is avoided.
>
> Signed-off-by: Mohan Kumar <[email protected]>
> Signed-off-by: Viswanath L <[email protected]>

Applied, thanks.


Takashi