linux-kernel - [PATCH 1/2] Staging: dgnc: dgnc_cls.c: Use usleep_range over udelay to improve coalescing processor wakeups

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Date:   Mon,  5 Dec 2016 16:45:56 +0100
From:   Shiva Kerdel <shiva@...ev.nl>
To:     lidza.louina@...il.com
Cc:     markh@...pro.net, gregkh@...uxfoundation.org,
        driverdev-devel@...uxdriverproject.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, Shiva Kerdel <shiva@...ev.nl>
Subject: [PATCH 1/2] Staging: dgnc: dgnc_cls.c: Use usleep_range over udelay to improve coalescing processor wakeups

In most cases, usleep_range is better than udelay, as the precise wakeup
from udelay is unnecessary.

usleep_range gives a much better chance of coalescing processor wakeups.

Signed-off-by: Shiva Kerdel <shiva@...ev.nl>
---
 drivers/staging/dgnc/dgnc_cls.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/dgnc/dgnc_cls.c b/drivers/staging/dgnc/dgnc_cls.c
index c20ffdd..6607243a 100644
--- a/drivers/staging/dgnc/dgnc_cls.c
+++ b/drivers/staging/dgnc/dgnc_cls.c
@@ -409,7 +409,7 @@ static void cls_assert_modem_signals(struct channel_t *ch)
 	writeb(out, &ch->ch_cls_uart->mcr);
 
 	/* Give time for the UART to actually drop the signals */
-	udelay(10);
+	usleep_range(10, 20);
 }
 
 static void cls_copy_data_from_queue_to_uart(struct channel_t *ch)
@@ -631,7 +631,7 @@ static void cls_flush_uart_read(struct channel_t *ch)
 	 * Presumably, this is a bug in this UART.
 	 */
 
-	udelay(10);
+	usleep_range(10, 20);
 }
 
 /*
@@ -1096,7 +1096,7 @@ static void cls_uart_init(struct channel_t *ch)
 
 	writeb(UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
 	       &ch->ch_cls_uart->isr_fcr);
-	udelay(10);
+	usleep_range(10, 20);
 
 	ch->ch_flags |= (CH_FIFO_ENABLED | CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
 
-- 
2.10.2