linux-kernel - Re: [PATCH 1/6] clk: sunxi: Add support for sun9i a80 usb clocks and resets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20141105094146.GB27686@lukather>
Date:	Wed, 5 Nov 2014 10:41:46 +0100
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Chen-Yu Tsai <wens@...e.org>,
	Kishon Vijay Abraham I <kishon@...com>,
	Mike Turquette <mturquette@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	linux-sunxi@...glegroups.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/6] clk: sunxi: Add support for sun9i a80 usb clocks and
 resets

Hi Russell,

On Tue, Nov 04, 2014 at 06:12:19PM +0000, Russell King - ARM Linux wrote:
> On Tue, Nov 04, 2014 at 12:07:14PM +0800, Chen-Yu Tsai wrote:
> > +	spin_lock_irqsave(data->lock, flags);
> > +
> > +	reg = readl(data->reg);
> > +	writel(reg & ~BIT(id), data->reg);
> > +
> > +	spin_unlock_irqrestore(data->lock, flags);
> 
> Don't we have generic support for atomic modification of register
> values?  Hmm, we have it for ARM only - atomic_io_modify() and
> atomic_io_modify_relaxed().
> 
> I guess we should push for those to become cross-arch if we end up
> with generic drivers shared between other architectures.

IIRC, the atomic MMIO accessors are doing exactly that, but with a
global lock for all MMIO accesses, while here we protect a single
register.

I'm not really sure that sharing this spinlock across the whole system
is worth it and scales that well.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

Download attachment "signature.asc" of type "application/pgp-signature" (820 bytes)