serial: asc: Adopt readl_/writel_relaxed()
commit08177ece596ccc9b9c194542c095c863c101fd11
authorDaniel Thompson <daniel.thompson@linaro.org>
Tue, 9 Sep 2014 10:03:57 +0000 (9 11:03 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 10 Sep 2014 13:59:41 +0000 (10 06:59 -0700)
treeb99406de5a0040610501496f2e26ddb7789fcb59
parentefb089517d2f34a58aceb600ab58b0ca3db1fa07
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>
drivers/tty/serial/st-asc.c