linux-kernel - Re: [PATCH 3/3] reset: socfpga: use readl/writel

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Date:	Tue, 05 Jul 2016 13:20:29 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Philipp Zabel <p.zabel@...gutronix.de>,
	linux-kernel@...r.kernel.org, Chen-Yu Tsai <wens@...e.org>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	Steffen Trumtrar <s.trumtrar@...gutronix.de>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 3/3] reset: socfpga: use readl/writel_relaxed

On Tuesday, July 5, 2016 12:17:52 PM CEST Philipp Zabel wrote:
> This just removes the rmb()/wmb() pair between register read and
> write. Since no relevant reads follow the rmb and no relevant writes
> precede the wmb, they should be safe to remove.
> 
> Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>

We should only do this if you are fixing a bug (which you don't mention
in the changelog), or if you can show a relevant performance
improvement. Is this code ever used in a fast path? If it is,
wouldn't that indicate a problem in some driver?

	Arnd