linux-kernel - [PATCH 3.17-rc3] serial: asc: Adopt readl_/writel

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Message-Id: <1409745651-3247-1-git-send-email-daniel.thompson@linaro.org>
Date:	Wed,  3 Sep 2014 13:00:51 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Daniel Thompson <daniel.thompson@...aro.org>,
	linux-kernel@...r.kernel.org, patches@...aro.org,
	linaro-kernel@...ts.linaro.org,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Patrice Chotard <patrice.chotard@...com>,
	Jiri Slaby <jslaby@...e.cz>, kernel@...inux.com,
	linux-serial@...r.kernel.org
Subject: [PATCH 3.17-rc3] serial: asc: Adopt readl_/writel_relaxed()

The architectures where this peripheral exists (ARM and SH) have expensive
implementations of writel(), reliant on spin locks and explicit L2 cache
management. These architectures provide a cheaper writel_relaxed() which
is much better suited to peripherals that do not perform DMA. The
situation with readl()/readl_relaxed()is similar although less acute.

This driver does not use DMA and will be more power efficient and more
robust (due to absense of spin locks during console I/O) if it uses the
relaxed variants.

This change means the driver is no longer portable and therefore no
longer suitable for compile testing.

Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@...il.com>
Cc: Patrice Chotard <patrice.chotard@...com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jslaby@...e.cz>
Cc: kernel@...inux.com
Cc: linux-serial@...r.kernel.org
Acked-by: Maxime Coquelin <maxime.coquelin@...com>
Acked-by: Peter Griffin <peter.griffin@...aro.org>
---
 drivers/tty/serial/Kconfig  | 2 +-
 drivers/tty/serial/st-asc.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 26cec64d..e9b1735 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1527,7 +1527,7 @@ config SERIAL_FSL_LPUART_CONSOLE
 config SERIAL_ST_ASC
 	tristate "ST ASC serial port support"
 	select SERIAL_CORE
-	depends on ARM || COMPILE_TEST
+	depends on ARM
 	help
 	  This driver is for the on-chip Asychronous Serial Controller on
 	  STMicroelectronics STi SoCs.
diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c
index 8b2d735..adadbc1 100644
--- a/drivers/tty/serial/st-asc.c
+++ b/drivers/tty/serial/st-asc.c
@@ -151,12 +151,12 @@ static inline struct asc_port *to_asc_port(struct uart_port *port)

 static inline u32 asc_in(struct uart_port *port, u32 offset)
 {
-	return readl(port->membase + offset);
+	return readl_relaxed(port->membase + offset);
 }

 static inline void asc_out(struct uart_port *port, u32 offset, u32 value)
 {
-	writel(value, port->membase + offset);
+	writel_relaxed(value, port->membase + offset);
 }

 /*
--
1.9.3

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