linux-kernel - Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to vexpress config interface

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] [day] [month] [year] [list]

Message-ID: <20130603131527.GC22821@e102568-lin.cambridge.arm.com>
Date:	Mon, 3 Jun 2013 14:15:27 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	"Jon Medhurst (Tixy)" <tixy@...aro.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Pawel Moll <Pawel.Moll@....com>,
	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	Achin Gupta <Achin.Gupta@....com>
Subject: Re: [RFC PATCH 2/3] drivers: mfd: vexpress: add timeout API to
 vexpress config interface

On Mon, Jun 03, 2013 at 01:03:50PM +0100, Jon Medhurst (Tixy) wrote:
> On Mon, 2013-06-03 at 12:52 +0100, Lorenzo Pieralisi wrote:
> > On Mon, Jun 03, 2013 at 11:15:32AM +0100, Jon Medhurst (Tixy) wrote:
> > > On Fri, 2013-05-24 at 13:53 +0100, Lorenzo Pieralisi wrote:
> > > > In case some transactions to the Serial Power Controller (SPC) are lost owing
> > > > to multiple operations handled at once by the M3 controller the OS needs to
> > > > rely on a configuration API that can time out so that failures do not result
> > > > in an unusable system.
> > > > 
> > > > This patch adds a timeout API to the vexpress config programming interface,
> > > > and refactors the existing read/write functions so that they can be reused
> > > > seamlessly on top of the newly defined API.
> > > 
> > > Isn't one of the main purposes of the config interface to serialise
> > > transactions to the config bus, so why would the SPC be handling
> > > multiple transactions at once? And if we can in fact loose transactions
> > > doesn't this mean we get random failures in the system? E.g. if this
> > > happened at boot in vexpress_spc_populate_opps then cpufreq will fail.
> > 
> > It has more to do with firmware carrying out background operations like
> > powering up a cluster when a DVFS is requested.
> 
> Would that make it drop transactions or just take a longer time to get
> around to servicing them?

It should just take longer to service them, that's what the behaviour
should be.

Lorenzo

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/