ALSA: ctxfi: Support PCM sync_stop

The driver invokes snd_pcm_period_elapsed() simply from the interrupt
handler.  Set card->sync_irq for enabling the missing sync_stop PCM
operation, as well as removing the superfluous synchronize_irq()
call.

Link: https://lore.kernel.org/r/20191210063454.31603-15-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/ctxfi/cthw20k1.c

@@ -1937,6 +1937,7 @@ static int hw_card_start(struct hw *hw)
 			goto error2;
 		}
 		hw->irq = pci->irq;
+		hw->card->sync_irq = hw->irq;
 	}
 
 	pci_set_master(pci);
@@ -1962,9 +1963,6 @@ static int hw_card_stop(struct hw *hw)
 	data = hw_read_20kx(hw, PLLCTL);
 	hw_write_20kx(hw, PLLCTL, (data & (~(0x0F<<12))));
 
-	/* TODO: Disable interrupt and so on... */
-	if (hw->irq >= 0)
-		synchronize_irq(hw->irq);
 	return 0;
 }
 

sound/pci/ctxfi/cthw20k2.c

@@ -2061,6 +2061,7 @@ static int hw_card_start(struct hw *hw)
 			goto error2;
 		}
 		hw->irq = pci->irq;
+		hw->card->sync_irq = hw->irq;
 	}
 
 	pci_set_master(pci);