usb: musb: cppi41: tweak hrtimer values

Intensive tests with USB audio devices connected to a musb host port have shown reproducible pops and clicks in both the playback and the capture stream. These are related to how the early_tx hrtimer is set up, and it turns out they can be fixed by reducing the timer's slack value from 40 to 25 us. Also, when the callback is ran without taking action, it should be rescheduled 20 us later instead of 50 us. Reported-and-tested-by: Sven Neumann <[email protected]> Signed-off-by: Daniel Mack <[email protected]> Signed-off-by: Felipe Balbi <[email protected]>
CamonZ · Sep 5, 2014 · a5e4aa4 · a5e4aa4
1 parent eb11ada
commit a5e4aa4
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
@@ -200,7 +200,7 @@ static enum hrtimer_restart cppi41_recheck_tx_req(struct hrtimer *timer)
 	if (!list_empty(&controller->early_tx_list)) {
 		ret = HRTIMER_RESTART;
 		hrtimer_forward_now(&controller->early_tx,
-				ktime_set(0, 50 * NSEC_PER_USEC));
+				ktime_set(0, 20 * NSEC_PER_USEC));
 	}
 
 	spin_unlock_irqrestore(&musb->lock, flags);
@@ -278,7 +278,7 @@ static void cppi41_dma_callback(void *private_data)
 
 			hrtimer_start_range_ns(&controller->early_tx,
 				ktime_set(0, usecs * NSEC_PER_USEC),
-				40 * NSEC_PER_USEC,
+				20 * NSEC_PER_USEC,
 				HRTIMER_MODE_REL);
 		}
 	}