From mboxrd@z Thu Jan 1 00:00:00 1970 From: peter.griffin@linaro.org (Peter Griffin) Date: Tue, 2 Sep 2014 14:42:58 +0100 Subject: [STLinux Kernel] [PATCH v11 17/19] serial: asc: Adopt readl_/writel_relaxed() In-Reply-To: <1409662853-29313-18-git-send-email-daniel.thompson@linaro.org> References: <1408466769-20004-1-git-send-email-daniel.thompson@linaro.org> <1409662853-29313-1-git-send-email-daniel.thompson@linaro.org> <1409662853-29313-18-git-send-email-daniel.thompson@linaro.org> Message-ID: <20140902134257.GA10125@griffinp-ThinkPad-X1-Carbon-2nd> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 02 Sep 2014, Daniel Thompson wrote: > 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 > Cc: Srinivas Kandagatla > Cc: Maxime Coquelin > Cc: Patrice Chotard > Cc: Greg Kroah-Hartman > Cc: Jiri Slaby > Cc: kernel at stlinux.com > Cc: linux-serial at vger.kernel.org Acked-by: Peter Griffin