Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751837AbdF1QHA (ORCPT ); Wed, 28 Jun 2017 12:07:00 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:59211 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751654AbdF1QGx (ORCPT ); Wed, 28 Jun 2017 12:06:53 -0400 Date: Wed, 28 Jun 2017 09:06:49 -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, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/2] drivers/watchdog: ASPEED reference dev tree properties for config Message-ID: <20170628160649.GB8915@roeck-us.net> References: <20170627211734.60477-1-cbostic@linux.vnet.ibm.com> <20170627211734.60477-3-cbostic@linux.vnet.ibm.com> <606a2e11-2d43-5204-0bb6-9c4415ee03df@roeck-us.net> <20170628145452.GA30968@roeck-us.net> <38e57720-9728-9377-2a16-adc8ce430ca0@linux.vnet.ibm.com> <20170628150846.GE30968@roeck-us.net> 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 Content-Length: 5822 Lines: 132 On Wed, Jun 28, 2017 at 10:55:08AM -0500, Christopher Bostic wrote: > > > On 6/28/17 10:08 AM, Guenter Roeck wrote: > >On Wed, Jun 28, 2017 at 09:59:22AM -0500, Christopher Bostic wrote: > >> > >>On 6/28/17 9:54 AM, Guenter Roeck wrote: > >>>On Wed, Jun 28, 2017 at 09:29:50AM -0500, Christopher Bostic wrote: > >>>>On 6/28/17 6:31 AM, Guenter Roeck wrote: > >>>>>On 06/27/2017 02:17 PM, Christopher Bostic wrote: > >>>>>>Reference the system device tree when configuring the watchdog > >>>>>>engines. Set external signal mode on timeout if specified. > >>>>>>Set system reset on timeout if specified. > >>>>>> > >>>>>>Signed-off-by: Christopher Bostic > >>>>>>--- > >>>>>>v2 - Change of_get_property() to of_property_read_bool() > >>>>>> - Remove redundant check for NULL struct device_node pointer > >>>>>> - Optional property names now start with prefix 'aspeed,' > >>>>>>--- > >>>>>> drivers/watchdog/aspeed_wdt.c | 13 +++++++++++-- > >>>>>> 1 file changed, 11 insertions(+), 2 deletions(-) > >>>>>> > >>>>>>diff --git a/drivers/watchdog/aspeed_wdt.c > >>>>>>b/drivers/watchdog/aspeed_wdt.c > >>>>>>index 1c65258..71ce5f5 100644 > >>>>>>--- a/drivers/watchdog/aspeed_wdt.c > >>>>>>+++ b/drivers/watchdog/aspeed_wdt.c > >>>>>>@@ -140,6 +140,7 @@ static int aspeed_wdt_probe(struct platform_device > >>>>>>*pdev) > >>>>>> { > >>>>>> struct aspeed_wdt *wdt; > >>>>>> struct resource *res; > >>>>>>+ struct device_node *np; > >>>>>> int ret; > >>>>>> wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL); > >>>>>>@@ -170,8 +171,16 @@ static int aspeed_wdt_probe(struct platform_device > >>>>>>*pdev) > >>>>>> * the SOC and not the full chip > >>>>>> */ > >>>>>> wdt->ctrl = WDT_CTRL_RESET_MODE_SOC | > >>>>>>- WDT_CTRL_1MHZ_CLK | > >>>>>>- WDT_CTRL_RESET_SYSTEM; > >>>>>>+ WDT_CTRL_1MHZ_CLK; > >>>>>>+ > >>>>>>+ np = pdev->dev.of_node; > >>>>>>+ if (of_property_read_bool(np, "aspeed,sys-reset")) > >>>>>>+ wdt->ctrl |= WDT_CTRL_RESET_SYSTEM; > >>>>>>+ > >>>>>For backward compatibility, this should default to WDT_CTRL_RESET_SYSTEM > >>>>>if no optional property is provided. > >>>>> > >>>>I had the logic inverted for this property in a previous patch. The > >>>>property was 'no-system-reset' so that when not present the default was to > >>>>set WDT_CTRL_RESET_SYSTEM. As it is in this patch, the only way to > >>>>indicate that no system reset is to be done is to not specify the property. > >>>>No system reset is desired under circumstances when another wdt engine is to > >>>>be responsible for this. Given the issue with backward compatibility > >>>>that's not a solution. Given this, would creating a property > >>>>'no-system-reset' be acceptable? > >>>> > >>>Sorry, I fail to see the problem. There are half a dozen properties. What is the > >>>problem with having a default if no property is specified ? Your default is "do > >>>nothing", which does not really make any sense to me. If the user wants the > >>>watchdog to do nothing, the simple means to accomplish that would be to not > >>>instantiate it. > >>> > >>>Sure, that means specifying "system-reset" is redundant, but I don't see a > >>>problem with that either. But I do see a problem with loading a watchdog driver > >>>that doesn't do anything. > >>> > >>>If there is really some use case where it makes sense to load a watchdog driver > >>>and have it do nothing, please explain and provide a respective devicetree > >>>property. "aspeed,do-nothing" (or whatever similar) doesn't sound good, but > >>>at least makes it obvious that the driver isn't doing anything besides > >>>creating a false sense of "the system is watchdog protected". > >>If system-reset is not wanted there are other properties that might still be > >>needed, for example > >>ARM reset only. We'd still want to instantiate it. > >> > >But then you would presumably specify that property, so there would be one. > >The question here is what to do if _no_ property is provided. > I agree that the default should be to perform a system reset when no > property is provided. I will make that change. Additionally for backwards > compatibility the SOC reset should be enabled by default when no property is > provided. The other parameters are not configured in the watchdog control > register if no property is provided. > > There is still a need to to configure for no system reset. For example, > optional parameter 'aspeed,no-sys-reset' that can be specified if system > reset is to be disabled. In addition the default 'SOC reset enabled' > behavior could be disabled with an optional parameter 'aspeed,no-soc-reset'. > > Why would there even be a need configure for no system reset? The external > mode 'wdt ext: External signal enable after timeout' can be sent off chip > even if system reset is disabled. The watchdog is doing something in this > case and would require wdt instantiation. > Wouldn't that be "aspeed,external-signal" ? Guenter > Hope this is more clear, sorry for the confusion. > > Thanks, > -Chris AST2500 Software Programming Guide > >Sorry, I don't get your point. > > > >Guenter > > > >>Thanks, > >>Chris > >>>Thanks, > >>>Guenter > >>> > >>> > >>>>Thanks, > >>>>Chris > >>>> > >>>>>>+ if (of_property_read_bool(np, "aspeed,external-signal")) > >>>>>>+ wdt->ctrl |= WDT_CTRL_WDT_EXT; > >>>>>>+ > >>>>>>+ writel(wdt->ctrl, wdt->base + WDT_CTRL); > >>>>>> if (readl(wdt->base + WDT_CTRL) & WDT_CTRL_ENABLE) { > >>>>>> aspeed_wdt_start(&wdt->wdd); > >>>>>> > >>-- > >>To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in > >>the body of a message to majordomo@vger.kernel.org > >>More majordomo info at http://vger.kernel.org/majordomo-info.html >