[PATCH v9 14/16] serial: asc: Adopt readl_/writel_relaxed()

[Daniel Thompson]

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 at linaro.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla at gmail.com>
Cc: Maxime Coquelin <maxime.coquelin at st.com>
Cc: Patrice Chotard <patrice.chotard at st.com>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Jiri Slaby <jslaby at suse.cz>
Cc: kernel at stlinux.com
Cc: linux-serial at vger.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 26cec64..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