From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH v11 17/19] serial: asc: Adopt readl_/writel_relaxed() Date: Tue, 2 Sep 2014 15:55:19 +0200 Message-ID: <5405CC47.2040907@st.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx07-00178001.pphosted.com ([62.209.51.94]:47055 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751500AbaIBN4U (ORCPT ); Tue, 2 Sep 2014 09:56:20 -0400 In-Reply-To: <1409662853-29313-18-git-send-email-daniel.thompson@linaro.org> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Daniel Thompson , Russell King Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kgdb-bugreport@lists.sourceforge.net, patches@linaro.org, linaro-kernel@lists.linaro.org, John Stultz , Anton Vorontsov , Colin Cross , kernel-team@android.com, Rob Herring , Linus Walleij , Ben Dooks , Catalin Marinas , Dave Martin , Fabio Estevam , Frederic Weisbecker , Nicolas Pitre , Srinivas Kandagatla , Patrice Chotard , Greg Kroah-Hartman , Jiri Slaby , kernel@stlinux.com, linux-serial@vger.kernel.org Hi Daniel, On 09/02/2014 03:00 PM, 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@stlinux.com > Cc: linux-serial@vger.kernel.org > --- > drivers/tty/serial/Kconfig | 2 +- > drivers/tty/serial/st-asc.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) You can add my: Acked-by: Maxime Coquelin thanks! Maxime From mboxrd@z Thu Jan 1 00:00:00 1970 From: maxime.coquelin@st.com (Maxime Coquelin) Date: Tue, 2 Sep 2014 15:55:19 +0200 Subject: [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: <5405CC47.2040907@st.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Daniel, On 09/02/2014 03:00 PM, 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 > --- > drivers/tty/serial/Kconfig | 2 +- > drivers/tty/serial/st-asc.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) You can add my: Acked-by: Maxime Coquelin thanks! Maxime From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754180AbaIBN4X (ORCPT ); Tue, 2 Sep 2014 09:56:23 -0400 Received: from mx07-00178001.pphosted.com ([62.209.51.94]:47055 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751500AbaIBN4U (ORCPT ); Tue, 2 Sep 2014 09:56:20 -0400 Message-ID: <5405CC47.2040907@st.com> Date: Tue, 2 Sep 2014 15:55:19 +0200 From: Maxime Coquelin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Daniel Thompson , Russell King Cc: , , , , , John Stultz , Anton Vorontsov , Colin Cross , , Rob Herring , Linus Walleij , Ben Dooks , Catalin Marinas , Dave Martin , Fabio Estevam , Frederic Weisbecker , Nicolas Pitre , Srinivas Kandagatla , Patrice Chotard , Greg Kroah-Hartman , Jiri Slaby , , Subject: Re: [PATCH v11 17/19] serial: asc: Adopt readl_/writel_relaxed() 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> In-Reply-To: <1409662853-29313-18-git-send-email-daniel.thompson@linaro.org> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.201.23.80] X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.12.52,1.0.27,0.0.0000 definitions=2014-09-02_04:2014-09-02,2014-09-02,1970-01-01 signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Daniel, On 09/02/2014 03:00 PM, 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@stlinux.com > Cc: linux-serial@vger.kernel.org > --- > drivers/tty/serial/Kconfig | 2 +- > drivers/tty/serial/st-asc.c | 4 ++-- > 2 files changed, 3 insertions(+), 3 deletions(-) You can add my: Acked-by: Maxime Coquelin thanks! Maxime