From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Thompson Subject: [PATCH 3.17-rc3 v2] serial: asc: Adopt readl_/writel_relaxed() Date: Tue, 9 Sep 2014 11:03:57 +0100 Message-ID: <1410257037-20030-1-git-send-email-daniel.thompson@linaro.org> References: <1409745651-3247-1-git-send-email-daniel.thompson@linaro.org> Return-path: Received: from mail-wg0-f44.google.com ([74.125.82.44]:34881 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752904AbaIIKEM (ORCPT ); Tue, 9 Sep 2014 06:04:12 -0400 Received: by mail-wg0-f44.google.com with SMTP id y10so2405558wgg.15 for ; Tue, 09 Sep 2014 03:04:11 -0700 (PDT) In-Reply-To: <1409745651-3247-1-git-send-email-daniel.thompson@linaro.org> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Greg Kroah-Hartman Cc: Daniel Thompson , linux-kernel@vger.kernel.org, patches@linaro.org, linaro-kernel@lists.linaro.org, Srinivas Kandagatla , Maxime Coquelin , Patrice Chotard , Jiri Slaby , kernel@stlinux.com, linux-serial@vger.kernel.org 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 Cc: Srinivas Kandagatla Cc: Maxime Coquelin Cc: Patrice Chotard Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: kernel@stlinux.com Cc: linux-serial@vger.kernel.org --- Notes: Changes since v1: * Added fallback to writel() to permit COMPILE_TESTing (review of Greg Kroah-Hartmam). 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 8b2d735..a3fc167 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 } /* -- 1.9.3