From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752615AbdGFUtA (ORCPT ); Thu, 6 Jul 2017 16:49:00 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:54925 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751980AbdGFUs5 (ORCPT ); Thu, 6 Jul 2017 16:48:57 -0400 Date: Thu, 6 Jul 2017 13:48:50 -0700 From: Guenter Roeck To: Christopher Bostic Cc: Rob Herring , mark.rutland@arm.com, devicetree@vger.kernel.org, linux-watchdog@vger.kernel.org, openbmc@lists.ozlabs.org, linux-kernel@vger.kernel.org, wim@iguana.be Subject: Re: [PATCH v3 1/2] drivers/watchdog: Add optional ASPEED device tree properties Message-ID: <20170706204850.GA20079@roeck-us.net> References: <20170629002811.87199-1-cbostic@linux.vnet.ibm.com> <20170629002811.87199-2-cbostic@linux.vnet.ibm.com> <21f28ed9-b73a-5c21-5557-bec1fef0d874@linux.vnet.ibm.com> <20170629150417.GA10226@roeck-us.net> <20170706143512.bmjv2gnoqp5ew4py@rob-hp-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: guenter@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: guenter@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 06, 2017 at 02:27:18PM -0500, Christopher Bostic wrote: > > > On 7/6/17 9:35 AM, Rob Herring wrote: > >On Thu, Jun 29, 2017 at 08:04:17AM -0700, Guenter Roeck wrote: > >>On Thu, Jun 29, 2017 at 08:39:59AM -0500, Christopher Bostic wrote: > >>> > >>>On 6/28/17 10:33 PM, Guenter Roeck wrote: > >>>>On 06/28/2017 05:28 PM, Christopher Bostic wrote: > >>>>>Describe device tree optional properties: > >>>>> > >>>>> * aspeed,arm-reet - ARM CPU reset on signal > >>>>> * aspeed,no-soc-reset - SOC reset on signal > >>>>> * aspeed,no-sys-reset - System reset on signal > >>>>> * aspeed,interrupt - Interrupt CPU on signal > >>>>> * aspeed,external-signal - Generate external signal (WDT1 and WDT2 > >>>>>only) > >>>>> * aspeed,alt-boot - Boot from alternate block on signal > >>>>> > >>>>>Signed-off-by: Christopher Bostic > >>>>>--- > >>>>>v3 - Invert soc and sys reset to 'no' to preserve backwards > >>>>> compatibility. SOC and SYS reset will be set by default > >>>>> without any optional parameters set > >>>>>v2 - Add 'aspeed,' prefix to all optional properties > >>>>> - Add arm-reset, soc-reset, interrupt, alt-boot properties > >>>>>--- > >>>>> .../devicetree/bindings/watchdog/aspeed-wdt.txt | 24 > >>>>>++++++++++++++++++++++ > >>>>> 1 file changed, 24 insertions(+) > >>>>> > >>>>>diff --git a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt > >>>>>b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt > >>>>>index c5e74d7..6f18005 100644 > >>>>>--- a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt > >>>>>+++ b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt > >>>>>@@ -8,9 +8,33 @@ Required properties: > >>>>> - reg: physical base address of the controller and length of memory > >>>>>mapped > >>>>> region > >>>>> +Optional properties: > >>>>>+ Signal behavior - Whenever a timeout occurs the watchdog can be > >>>>>programmed > >>>>>+ to generate/not generate 6 types of signals: > >>>>>+ > >>>>>+ - aspeed,arm-reset: If property is present then reset ARM CPU only. > >>>>>+ If not specified no ARM CPU reset is done. > >>>>>+ > >>>>>+ - aspeed,no-soc-reset: If property is present then do not reset SOC. > >>>>>+ If not specified then SOC reset is done. > >>>>>+ > >>>>>+ - aspeed,no-sys-reset: If property is present then do not reset > >>>>>system. > >>>>>+ Typcally used in tandem with 'aspeed-external-signal' > >>>>Is this correct ? As I understand the datasheet, it could also used in > >>>>tandem with > >>>>aspeed,interrupt. > >>>True, that should be documented. Will add that. > >>>>>+ If not specified then system reset is done. > >>>>>+ > >>>>I'll leave it up to Rob to decide, but for my part I don't understand > >>>>no-soc-reset. > >>>As the aspeed watchdog driver exists prior to this change an SOC reset is > >>>done by > >>>default. In order to preserve backwards compatibility a missing optional > >>>property > >>>should result in default behavior. I however need to be able to specify > >>>that SOC > >>>reset be disabled in some way. This goes back to our discussion about why > >>>we'd > >>>ever want to disable SYSTEM reset in the first place. Same reasoning > >>>applies for > >>>SOC reset. > >>> > >>>>I would instead use four properties. > >>>> > >>>> aspeed,arm-reset > >>>> aspeed,soc-reset > >>>Per my response above I think it should remain as aspeed,no-soc-reset due to > >>>backwards compatibility requirements. > >>The same can be accomplished with "aspeed,no-reset", which would avoid the, in > >>my opinion, awkward "no-{sys,soc}-reset" poperties. > >> > >>>> aspeed,sys-reset (which is the default) > >>>Again as per our discussion yesterday I need some way to specify how system > >>>reset is to be done. For backwards compatibility, a lack of parameter here > >>>would > >>>result in a system reset being configured. Only way to indicate to the > >>>driver > >>>that no system reset is to be done is to indicate 'no' system reset in the > >>>optional > >>>parameter. > >>Or "aspeed,no-reset". > >> > >>>> aspeed,no-reset > >>>This parameter seems ambiguous as we could be doing a 'no system reset' > >>>or a 'no SOC reset' in theory. > >>{arm,soc,sys}-reset are mutually exclusive per datasheet, and there is a > >>separate configuration bit which enables the reset in the first place. > >>I don't see how that is ambiguous. > >> > >>Anyway, I don't think we are making any progress here. Let's wait for > >>guidance from Rob. > >I tend to agree with Guenter. > > > >Maybe using the form 'aspeed,reset-type = "cpu|soc|system"' would be > >more aligned to the type of reset being mutually exclusive. > > OK I'll update to this method. > Maybe add 'aspeed,reset-type = "none"' ? The default (no property) would then be "system". Thanks, Guenter