From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Boyd Subject: Re: [PATCH v2 1/2] devicetree: add binding for generic mmio clocksource Date: Fri, 9 Oct 2015 11:46:32 -0700 Message-ID: <20151009184632.GR26883@codeaurora.org> References: <1444232234-2133-1-git-send-email-mans@mansr.com> <20151007154727.GC28981@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Rob Herring Cc: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= , Mark Rutland , Pawel Moll , Ian Campbell , Kumar Gala , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org On 10/09, Rob Herring wrote: > +Stephen who has worked on this code. >=20 > On Fri, Oct 9, 2015 at 11:19 AM, M=E5ns Rullg=E5rd w= rote: > > M=E5ns Rullg=E5rd writes: > > > >> Rob Herring writes: > >> > >>> On Wed, Oct 7, 2015 at 11:47 AM, M=E5ns Rullg=E5rd wrote: > >>>> What would be a proper way to select a sched_clock source? I re= alise > >>>> it's a Linux-specific thing and DT is supposed to be generic, bu= t the > >>>> information must be provided somehow. > >>> > >>> The kernel already has some logic to do this. Most number of bits > >>> followed by highest frequency will be the winning sched_clock. Yo= u > >>> might also want to look at things like always on or not. > >> > >> The problem is that sched_clock_register() doesn't take a pointer = to be > >> passed back to the read_sched_clock callback like most interfaces = of > >> this type do. This means the callback must use global variables s= et up > >> before the register call, but at that time there's no way of knowi= ng > >> which one will be used. If there were a way of getting a pointer = to the > >> callback, it would be a simple matter of registering all instances= and > >> letting the kernel choose which to use. > > > > Anyone got a comment on this? Do I have to send a patch adding thi= s > > before anyone will tell me why it's a bad idea? (That method almos= t > > always works.) >=20 > Adding a ptr to the callback seems fine to me. >=20 Does that mean a flag day? Urgh. Pain. I'm not opposed to adding a pointer, in fact it might be better for performance so that we don't take a cache miss in read() functions that need to load some pointer. We were talking about that problem a few months ago, but nothing came of it. --=20 Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html