ALSA: hda: Clear RIRB status before reading WP

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.

Bug 2533543

Change-Id: Ib79ee9534cdb7a649af32c46f0c8d934c6c28861
Signed-off-by: Mohan Kumar <[email protected]>
Signed-off-by: Viswanath L <[email protected]>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-4.9/+/2291384
Tested-by: mobile promotions <[email protected]>
Reviewed-by: Sharad Gupta <[email protected]>
Reviewed-by: mobile promotions <[email protected]>
GVS: Gerrit_Virtual_Submit

Author: mkumard

sound/pci/hda/hda_controller.c

@@ -1205,16 +1205,23 @@ 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);