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From: Shiva Kerdel <shiva@exdev.nl>
To: lidza.louina@gmail.com
Cc: markh@compro.net, gregkh@linuxfoundation.org,
	driverdev-devel@linuxdriverproject.org,
	devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org,
	Shiva Kerdel <shiva@exdev.nl>
Subject: [PATCH v2] Staging: dgnc: dgnc_*.c: Use usleep_range over udelay to improve coalescing processor wakeups
Date: Tue,  6 Dec 2016 09:59:58 +0100	[thread overview]
Message-ID: <20161206085958.5286-1-shiva@exdev.nl> (raw)

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@exdev.nl>
---
Changes for v2:
    - Squashed the two commits to one patch.

 drivers/staging/dgnc/dgnc_cls.c |  6 +++---
 drivers/staging/dgnc/dgnc_neo.c | 10 +++++-----
 2 files changed, 8 insertions(+), 8 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);
 
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

             reply	other threads:[~2016-12-06  9:27 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-06  8:59 Shiva Kerdel [this message]
2016-12-06  9:12 ` [PATCH v2] Staging: dgnc: dgnc_*.c: Use usleep_range over udelay to improve coalescing processor wakeups Greg KH
2016-12-06 10:01   ` Shiva Kerdel

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