From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [PATCH 3.17-rc3] serial: asc: Adopt readl_/writel_relaxed() Date: Mon, 8 Sep 2014 16:27:27 -0700 Message-ID: <20140908232727.GA8970@kroah.com> References: <1409745651-3247-1-git-send-email-daniel.thompson@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36430 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755213AbaIHX12 (ORCPT ); Mon, 8 Sep 2014 19:27:28 -0400 Content-Disposition: inline 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: Daniel Thompson Cc: linux-kernel@vger.kernel.org, patches@linaro.org, linaro-kernel@lists.linaro.org, Srinivas Kandagatla , Patrice Chotard , Jiri Slaby , kernel@stlinux.com, linux-serial@vger.kernel.org On Wed, Sep 03, 2014 at 01:00:51PM +0100, 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: Patrice Chotard > Cc: Greg Kroah-Hartman > Cc: Jiri Slaby > Cc: kernel@stlinux.com > Cc: linux-serial@vger.kernel.org > Acked-by: Maxime Coquelin > Acked-by: Peter Griffin > --- > drivers/tty/serial/Kconfig | 2 +- > drivers/tty/serial/st-asc.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig > index 26cec64d..e9b1735 100644 > --- a/drivers/tty/serial/Kconfig > +++ b/drivers/tty/serial/Kconfig > @@ -1527,7 +1527,7 @@ config SERIAL_FSL_LPUART_CONSOLE > config SERIAL_ST_ASC > tristate "ST ASC serial port support" > select SERIAL_CORE > - depends on ARM || COMPILE_TEST > + depends on ARM I really don't like stuff that does this, sorry. I want to test build as many drivers as I can. COMPILE_TEST does not mean that the driver is "portable", only that it builds properly on all platforms. > help > This driver is for the on-chip Asychronous Serial Controller on > STMicroelectronics STi SoCs. > diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c > index 8b2d735..adadbc1 100644 > --- a/drivers/tty/serial/st-asc.c > +++ b/drivers/tty/serial/st-asc.c > @@ -151,12 +151,12 @@ 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); What plaforms do not provide readl_relaxed()? thanks, greg k-h