Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753483AbdF2PEV (ORCPT ); Thu, 29 Jun 2017 11:04:21 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:43237 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751974AbdF2PEU (ORCPT ); Thu, 29 Jun 2017 11:04:20 -0400 Date: Thu, 29 Jun 2017 08:04:17 -0700 From: Guenter Roeck To: Christopher Bostic Cc: wim@iguana.be, robh+dt@kernel.org, mark.rutland@arm.com, joel@jms.id.au, linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org, openbmc@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/2] drivers/watchdog: Add optional ASPEED device tree properties Message-ID: <20170629150417.GA10226@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <21f28ed9-b73a-5c21-5557-bec1fef0d874@linux.vnet.ibm.com> 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 Content-Length: 5030 Lines: 143 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. Guenter > > > >There should also be a note explaining that the above are mutually > >exclusive. > > > OK, will add that. > > >>+ - aspeed,interrupt: If property is present then interrupt CPU. > >>+ If not specified then don't interrupt CPU. > >>+ > >>+ - aspeed,external-signal: If property is present then signal is sent > >>to > >>+ external reset counter (only WDT1 and WDT2). If not > >>+ specified no external signal is sent. > > > >For consistency, either add an empty line here or remove the empty lines > >above > > Will fix. > > Thanks, > Chris > > > >>+ - aspeed,alt-boot: If property is present then boot from alternate > >>block. > >>+ > >> Example: > >> wdt1: watchdog@1e785000 { > >> compatible = "aspeed,ast2400-wdt"; > >> reg = <0x1e785000 0x1c>; > >>+ aspeed,no-sys-reset; > >>+ aspeed,external-signal; > >> }; > >> > > >