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

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Date:   Mon,  5 Dec 2016 16:45:57 +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 2/2] Staging: dgnc: dgnc_neo.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_neo.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/dgnc/dgnc_neo.c b/drivers/staging/dgnc/dgnc_neo.c
index 3eefefe..20bc271 100644
--- a/drivers/staging/dgnc/dgnc_neo.c
+++ b/drivers/staging/dgnc/dgnc_neo.c
@@ -1352,7 +1352,7 @@ static void neo_flush_uart_write(struct channel_t *ch)
 		 */
 		tmp = readb(&ch->ch_neo_uart->isr_fcr);
 		if (tmp & 4)
-			udelay(10);
+			usleep_range(10, 20);
 		else
 			break;
 	}
@@ -1384,7 +1384,7 @@ static void neo_flush_uart_read(struct channel_t *ch)
 		 */
 		tmp = readb(&ch->ch_neo_uart->isr_fcr);
 		if (tmp & 2)
-			udelay(10);
+			usleep_range(10, 20);
 		else
 			break;
 	}
@@ -1616,7 +1616,7 @@ static void neo_assert_modem_signals(struct channel_t *ch)
 	neo_pci_posting_flush(ch->ch_bd);
 
 	/* Give time for the UART to actually raise/drop the signals */
-	udelay(10);
+	usleep_range(10, 20);
 }
 
 static void neo_send_start_character(struct channel_t *ch)
@@ -1628,7 +1628,7 @@ static void neo_send_start_character(struct channel_t *ch)
 		ch->ch_xon_sends++;
 		writeb(ch->ch_startc, &ch->ch_neo_uart->txrx);
 		neo_pci_posting_flush(ch->ch_bd);
-		udelay(10);
+		usleep_range(10, 20);
 	}
 }
 
@@ -1641,7 +1641,7 @@ static void neo_send_stop_character(struct channel_t *ch)
 		ch->ch_xoff_sends++;
 		writeb(ch->ch_stopc, &ch->ch_neo_uart->txrx);
 		neo_pci_posting_flush(ch->ch_bd);
-		udelay(10);
+		usleep_range(10, 20);
 	}
 }
 
-- 
2.10.2