From 08177ece596ccc9b9c194542c095c863c101fd11 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Tue, 9 Sep 2014 11:03:57 +0100 Subject: [PATCH] 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 Acked-by: Srinivas Kandagatla Cc: Maxime Coquelin Cc: Patrice Chotard Cc: Jiri Slaby Cc: kernel@stlinux.com Cc: linux-serial@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/st-asc.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c index 8b2d7356611d..a3fc1678d2b9 100644 --- a/drivers/tty/serial/st-asc.c +++ b/drivers/tty/serial/st-asc.c @@ -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) { - return readl(port->membase + offset); + return readl_relaxed(port->membase + offset); } 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); +#endif } /*