Commit 08177ece authored Sep 09, 2014 by Daniel Thompson Committed by Greg Kroah-Hartman Sep 10, 2014

serial: asc: Adopt readl_/writel_relaxed()



The architectures supported by this driver, 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 absence of spin locks during console I/O) if it uses the
relaxed variants.

The driver supports COMPILE_TEST and therefore falls back to writel()
when writel_relaxed() does not exist.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@gmail.com>
Cc: Maxime Coquelin <maxime.coquelin@st.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: kernel@stlinux.com
Cc: linux-serial@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent efb08951

drivers/tty/serial/st-asc.c

+5 −1

Original line number	Original line	Diff line number	Diff line
	@@ -151,12 +151,16 @@ static inline struct asc_port to_asc_port(struct uart_port port)

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

	/*		/*