From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Thu, 7 Mar 2013 11:49:50 +0000 Subject: [PATCH] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue In-Reply-To: References: <20130305105251.GL17833@n2100.arm.linux.org.uk> <20130307005119.GY17833@n2100.arm.linux.org.uk> Message-ID: <20130307114950.GF17833@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Mar 07, 2013 at 10:03:28AM +0800, Viresh Kumar wrote: > On 7 March 2013 08:51, Russell King - ARM Linux wrote: > > On Thu, Mar 07, 2013 at 08:32:37AM +0800, Viresh Kumar wrote: > >> On 5 March 2013 18:52, Russell King - ARM Linux wrote: > >> > On Tue, Mar 05, 2013 at 12:52:41PM +0800, Viresh Kumar wrote: > >> >> + clk[cluster] = clk_get(NULL, name); > >> >> + if (!IS_ERR_OR_NULL(clk[cluster])) { > >> > > >> > NAK. Two reasons. > >> > > >> > 1. IS_ERR_OR_NULL. You know about this, it's been on the list several > >> > times. > >> > >> Hey, i had a second thought about this one and i have some other opinion > >> here. This is a cpufreq driver and we need clock support for sure here, we > >> can't work without it. And so here is the latest fixup: > > > > NAK. You just don't understand. > > Poor me!! > > I still remember the huge discussions we had during "clk: Add non > CONFIG_HAVE_CLK routines" patchset. > > For others: https://lkml.org/lkml/2012/4/24/389 > > Back to the discussion, I understand that clk_get() just returns a cookie and > NULL is not an error and so it shouldn't be treated specially. And that's what > we do with most of our drivers as all other clk routines (clk_get[set]_rate()) > have safe guards against the NULL clk, and they wouldn't complain. > > The special case we have in a cpufreq driver is, we can't work with > zero returned > from clk_get_rate()... That will make cpufreq driver work badly. So how is this different from any other clock which may also return zero from its clk_get_rate() ? If that's the condition you want to check for, call clk_get_rate() after a successful clk_get*() and check for the condition. Don't go treating the cookie somehow specially. You're *assuming* a behaviour that is inappropriate for the side of the interface you're working with.