From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932665AbbJIV7V (ORCPT ); Fri, 9 Oct 2015 17:59:21 -0400 Received: from unicorn.mansr.com ([81.2.72.234]:38861 "EHLO unicorn.mansr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932457AbbJIV7T convert rfc822-to-8bit (ORCPT ); Fri, 9 Oct 2015 17:59:19 -0400 From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= To: Stephen Boyd Cc: Rob Herring , Mark Rutland , Pawel Moll , Ian Campbell , Kumar Gala , "devicetree\@vger.kernel.org" , "linux-kernel\@vger.kernel.org" Subject: Re: [PATCH v2 1/2] devicetree: add binding for generic mmio clocksource References: <1444232234-2133-1-git-send-email-mans@mansr.com> <20151007154727.GC28981@leverpostej> <20151009184632.GR26883@codeaurora.org> Date: Fri, 09 Oct 2015 22:59:18 +0100 In-Reply-To: <20151009184632.GR26883@codeaurora.org> (Stephen Boyd's message of "Fri, 9 Oct 2015 11:46:32 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Stephen Boyd writes: > On 10/09, Rob Herring wrote: >> +Stephen who has worked on this code. >> >> On Fri, Oct 9, 2015 at 11:19 AM, Måns Rullgård wrote: >> > Måns Rullgård writes: >> > >> >> Rob Herring writes: >> >> >> >>> On Wed, Oct 7, 2015 at 11:47 AM, Måns Rullgård wrote: >> >>>> What would be a proper way to select a sched_clock source? I realise >> >>>> it's a Linux-specific thing and DT is supposed to be generic, but 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. You >> >>> 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 set up >> >> before the register call, but at that time there's no way of knowing >> >> 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 this >> > before anyone will tell me why it's a bad idea? (That method almost >> > always works.) >> >> Adding a ptr to the callback seems fine to me. >> > > 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. I've sent a patch. Let the flames begin. -- Måns Rullgård mans@mansr.com