diff options
| author | Daniel Thompson <daniel.thompson@linaro.org> | 2014-09-09 14:03:57 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-09-10 17:59:41 +0400 |
| commit | 08177ece596ccc9b9c194542c095c863c101fd11 (patch) | |
| tree | b99406de5a0040610501496f2e26ddb7789fcb59 /drivers/tty | |
| parent | efb089517d2f34a58aceb600ab58b0ca3db1fa07 (diff) | |
| download | linux-08177ece596ccc9b9c194542c095c863c101fd11.tar.xz | |
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>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/st-asc.c | 6 |
1 files changed, 5 insertions, 1 deletions
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 } /* |