linux-kernel - Re: [PATCH v11 17/19] serial: asc: Adopt readl_/writel

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Message-ID: <5405CC47.2040907@st.com>
Date:	Tue, 2 Sep 2014 15:55:19 +0200
From:	Maxime Coquelin <maxime.coquelin@...com>
To:	Daniel Thompson <daniel.thompson@...aro.org>,
	Russell King <linux@....linux.org.uk>
Cc:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<kgdb-bugreport@...ts.sourceforge.net>, <patches@...aro.org>,
	<linaro-kernel@...ts.linaro.org>,
	John Stultz <john.stultz@...aro.org>,
	Anton Vorontsov <anton.vorontsov@...aro.org>,
	Colin Cross <ccross@...roid.com>, <kernel-team@...roid.com>,
	Rob Herring <robherring2@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Martin <Dave.Martin@....com>,
	Fabio Estevam <festevam@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Nicolas Pitre <nico@...aro.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Patrice Chotard <patrice.chotard@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, <kernel@...inux.com>,
	<linux-serial@...r.kernel.org>
Subject: Re: [PATCH v11 17/19] serial: asc: Adopt readl_/writel_relaxed()

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 <daniel.thompson@...aro.org>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@...il.com>
> Cc: Maxime Coquelin <maxime.coquelin@...com>
> Cc: Patrice Chotard <patrice.chotard@...com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jiri Slaby <jslaby@...e.cz>
> Cc: kernel@...inux.com
> Cc: linux-serial@...r.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 <maxime.coquelin@...com>

thanks!
Maxime

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