From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758113AbcBDXxU (ORCPT ); Thu, 4 Feb 2016 18:53:20 -0500 Received: from mail-yw0-f180.google.com ([209.85.161.180]:35430 "EHLO mail-yw0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757530AbcBDXxT (ORCPT ); Thu, 4 Feb 2016 18:53:19 -0500 X-Greylist: delayed 423 seconds by postgrey-1.27 at vger.kernel.org; Thu, 04 Feb 2016 18:53:19 EST MIME-Version: 1.0 In-Reply-To: <20160204230814.GA4847@rob-hp-laptop> References: <1454406981-4692-1-git-send-email-andy.yan@rock-chips.com> <1454407151-4751-1-git-send-email-andy.yan@rock-chips.com> <20160204230814.GA4847@rob-hp-laptop> Date: Thu, 4 Feb 2016 15:46:15 -0800 Message-ID: Subject: Re: [PATCH v3 1/4] dt-bindings: power: reset: add document for reboot-mode driver From: John Stultz To: Rob Herring Cc: Andy Yan , Arnd Bergmann , Moritz Fischer , Matthias Brugger , Kumar Gala , Ian Campbell , Catalin Marinas , =?UTF-8?Q?Heiko_St=C3=BCbner?= , Sebastian Reichel , Dmitry Eremin-Solenikov , Alexandre Belloni , Jun Nie , =?UTF-8?Q?Pawe=C5=82_Moll?= , Will Deacon , "open list:ARM/Rockchip SoC..." , Caesar Wang , devicetree@vger.kernel.org, Linux PM list , Russell King - ARM Linux , mbrugger@suse.com, "linux-arm-kernel@lists.infradead.org" , Lorenzo Pieralisi , lkml , Richard Weinberger , David Woodhouse , Mark Rutland 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 Thu, Feb 4, 2016 at 3:08 PM, Rob Herring wrote: > On Tue, Feb 02, 2016 at 05:59:11PM +0800, Andy Yan wrote: >> add device tree bindings document for reboot-mode driver >> >> Signed-off-by: Andy Yan >> >> --- >> >> Changes in v3: >> - descirbe all reboot mode as properity instead of subnode >> >> Changes in v2: None >> Changes in v1: None >> >> .../bindings/power/reset/reboot-mode.txt | 26 ++++++++++++++++ >> .../bindings/power/reset/syscon-reboot-mode.txt | 36 ++++++++++++++++++++++ >> 2 files changed, 62 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/power/reset/reboot-mode.txt >> create mode 100644 Documentation/devicetree/bindings/power/reset/syscon-reboot-mode.txt >> >> diff --git a/Documentation/devicetree/bindings/power/reset/reboot-mode.txt b/Documentation/devicetree/bindings/power/reset/reboot-mode.txt >> new file mode 100644 >> index 0000000..517080f >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/power/reset/reboot-mode.txt >> @@ -0,0 +1,26 @@ >> +Generic reboot mode core map driver >> + >> +This driver get reboot mode arguments and call the write >> +interface to stores the magic value in special register >> +or ram . Then the bootloader can read it and take different >> +action according the argument stored. >> + >> +All mode properties are vendor specific, it is a indication to tell > > The values should be vendor specific. The property names should not. We > can allow vendor specific ones, but we need to have a common set. > >> +the bootloder what to do when the system reboot, and should be named >> +as mode-xxx = (xxx is mode name). >> + >> +- mode-normal: Normal reboot mode, system reboot with command "reboot". >> +- mode-recovery: Android Recovery mode, it is a mode to format the device or update a new image. >> +- mode-fastboot: Android fastboot mode, it's a mode to re-flash partitions on the device. >> +- mode-loader: A bootloader mode, it's a mode used to download image on Rockchip platform, >> + usually used in development. >> +- mode-maskrom: It's a mode to download bootloader on Rockchip platform. >> + >> +Example: >> + reboot-mode { >> + mode-normal = ; >> + mode-recovery = ; >> + mode-fastboot = ; > > I tend to agree with John on calling this mode-bootloader. > > OTOH, fastboot is more specific about what the mode is. The name in DT > and the userspace name don't necessarily have to be the same. Wait. This is a bit confusing. The utility of adding a property name and using that name be the reboot command parsed for made sense (compared to earlier versions which had command strings) as it made the dts more terse. But it sounds here like you're suggesting we should have some logic in the driver that translates "reboot fastboot" to mode-bootloader or vice versa. >> + mode-loader = ; > > This one needs a better name. Maybe it should be 'rockchip,mode-loader' > as it is vendor specific. Either way, loader is vague. Perhaps > rockchip,mode-bl-download? Hrm. So how what reboot command do you expect to trigger that? Though I do like the vendor specific prefix here, as it clarifies how universal the command is (and its easy add standard commands if they become more established and remap things in the future). > >> + mode-maskrom = ; > > I think this should be "mode-rom-download". I think one of the difficult things here is that there's no real standards for all bios/bootloader modes. So they are somewhat firmware/bootloader/device specific, and thus we need something that is flexible enough to allow lots of different modes to be easily specified. That said, this does expose a userspace interface (though one could argue kernel ABI doesn't cross reboots :) so we should try to have some consistency so the same userspace can work on various devices. I do think the "bootloader" and "recovery" arguments are somewhat defacto standards, well established on most android devices. I think here the concern is rockchip probably has some userspace that is already using "reboot maskrom" or "reboot loader" for their own uses. And its a bit of a pain to ask that userspace to be reworked to use "reboot rom-download" or "reboot rockchip,rom-download" depending on how we try to deal with these. (Granted, non-upstream interfaces aren't official, so that is their risk somewhat, but we avoid being smug about that :) Another part of the issue is there isn't really a way to probe for reboot cmd capability here. As much as I'd rather not complicate things, one couldn't easily extend existing userspace to work with current kernels as well as future kernels, since the reboot with an invalid command won't fail. The machine still resets. So you can't try one and fallback to the other. Maybe there needs to be a sysfs entry with the list of the supported commands? thanks -john