Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964885AbaFJIMR (ORCPT ); Tue, 10 Jun 2014 04:12:17 -0400 Received: from mail-ob0-f169.google.com ([209.85.214.169]:53361 "EHLO mail-ob0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933535AbaFJIMM (ORCPT ); Tue, 10 Jun 2014 04:12:12 -0400 MIME-Version: 1.0 In-Reply-To: <20140609223831.GB16889@e102568-lin.cambridge.arm.com> References: <1402090985-8061-1-git-send-email-dianders@chromium.org> <20140607181221.GB25068@e102568-lin.cambridge.arm.com> <20140609223831.GB16889@e102568-lin.cambridge.arm.com> Date: Tue, 10 Jun 2014 13:42:11 +0530 Message-ID: Subject: Re: [PATCH] ARM: EXYNOS: mcpm: Don't rely on firmware's secondary_cpu_start From: Chander Kashyap To: Lorenzo Pieralisi Cc: Doug Anderson , Kukjin Kim , Nicolas Pitre , Abhilash Kesavan , Andrew Bresticker , Inderpal Singh , Thomas Abraham , "olof@lixom.net" , Tushar Behera , Kevin Hilman , Javier Martinez Canillas , "linux-samsung-soc@vger.kernel.org" , "linux@arm.linux.org.uk" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10 June 2014 04:08, Lorenzo Pieralisi wrote: > On Mon, Jun 09, 2014 at 06:03:31PM +0100, Doug Anderson wrote: > > [...] > >> Cold boot and resume from suspend are detected via various special >> flags in various special locations. Resume from suspend looks at >> INFORM1 (0x10048004) for flags. This register is 0 during a cold boot >> and has special values set by the kernel at resume time. >> >> It also looks as if some code looks at 0x10040900 (PMU_SPARE0) to help >> tell initial cold boot and secondary CPU bringup. > > Ok, thanks a lot. It looks like firmware paths should be ready to > detect cold vs warm boot, and hopefully do not rely on a specific > MPIDR to come up first out of power states. > >> > I am asking to check if on this platform CPUidle (where the notion of >> > primary CPU disappears) has a chance to run properly. >> >> I believe it should be possible, but we don't have CPUidle implemented >> in our current system. Abhilash may be able to comment more. > Cpuidle is implemented for exynos5420, and is tested on chromebook. > I am interested in more insights, that's very helpful thanks. > >> > Probably CPUidle won't attain idle states where IRAM content is lost, but I >> > am still worried about the primary vs secondaries firmware boot behaviour. >> >> I don't think iRAM can be turned off for CPUidle. Yes thats true. > > It might be added a system state but I doubt that too and if you are > relying on registers for jump addresses that's not even a problem in > the first place. > >> > What happens on reboot from suspend to RAM (or to put it differently, >> > what does secure firmware do on reboot from suspend to RAM - in >> > particular how is the "jump" address to bootloader/kernel set ?) >> >> Should be described above now. > > Thank you very much. > > Lorenzo > > -- > To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- with warm regards, Chander Kashyap -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/