linux-kernel - [PATCH v11 17/19] serial: asc: Adopt readl_/writel

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Date:	Tue,  2 Sep 2014 14:00:51 +0100
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Russell King <linux@....linux.org.uk>
Cc:	Daniel Thompson <daniel.thompson@...aro.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kgdb-bugreport@...ts.sourceforge.net, patches@...aro.org,
	linaro-kernel@...ts.linaro.org,
	John Stultz <john.stultz@...aro.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Colin Cross <ccross@...roid.com>, kernel-team@...roid.com,
	Rob Herring <robherring2@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Martin <Dave.Martin@....com>,
	Fabio Estevam <festevam@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Nicolas Pitre <nico@...aro.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Patrice Chotard <patrice.chotard@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, kernel@...inux.com,
	linux-serial@...r.kernel.org
Subject: [PATCH v11 17/19] 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: Maxime Coquelin <maxime.coquelin@...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
---
 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 2b5eb6e..df709ee 100644
--- a/drivers/tty/serial/st-asc.c
+++ b/drivers/tty/serial/st-asc.c
@@ -152,12 +152,12 @@ 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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