From a5e4aa4d770ae96da52c8fa035751d2046e2434f Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@zonque.org>
Date: Wed, 3 Sep 2014 17:21:24 +0200
Subject: 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 <neumann@teufel.de>
Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
---
 drivers/usb/musb/musb_cppi41.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'drivers/usb/musb/musb_cppi41.c')

diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index 47ae6455d073..ecdd6328aafb 100644
--- 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);
 		}
 	}
-- 
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