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Date:   Fri, 26 Apr 2019 13:17:19 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Anson Huang <anson.huang@nxp.com>
Cc:     "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "festevam@gmail.com" <festevam@gmail.com>,
        "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
        Aisheng Dong <aisheng.dong@nxp.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH 2/2] watchdog: imx_sc: Add pretimeout support
Message-ID: <20190426201719.GB21075@roeck-us.net>
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On Thu, Apr 25, 2019 at 05:44:45AM +0000, Anson Huang wrote:
> Hi, Guenter
> 
> > -----Original Message-----
> > From: Guenter Roeck [mailto:groeck7@gmail.com] On Behalf Of Guenter
> > Roeck
> > Sent: Thursday, April 25, 2019 12:04 PM
> > To: Anson Huang <anson.huang@nxp.com>; shawnguo@kernel.org;
> > s.hauer@pengutronix.de; kernel@pengutronix.de; festevam@gmail.com;
> > wim@linux-watchdog.org; Aisheng Dong <aisheng.dong@nxp.com>; linux-
> > arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> > watchdog@vger.kernel.org
> > Cc: dl-linux-imx <linux-imx@nxp.com>
> > Subject: Re: [PATCH 2/2] watchdog: imx_sc: Add pretimeout support
> > 
> > On 4/24/19 6:14 PM, Anson Huang wrote:
> > > i.MX system controller watchdog can support pretimeout IRQ via general
> > > SCU MU IRQ, it depends on IMX_SCU and driver MUST be probed after SCU
> > > IPC ready, then enable corresponding SCU IRQ group and register SCU
> > > IRQ notifier, when watchdog pretimeout IRQ fires, SCU MU IRQ will be
> > > handled and watchdog pretimeout notifier will be called to handle the
> > > event.
> > >
> > 
> > Ah, here is the missing patch.
> > 
> > As mentioned in my other reply, the watchdog driver does now depend on
> > the SCU IPC handle and should be instantiated accordingly.
> > Using -EPROBE_DEFER to work around bad dependencies is not a solution.
> 
> So, I have to move the i.MX system controller watchdog node into the i.MX SCU
> node in DT file now? As it depends on i.MX SCU firmware. If so, should I remove the

Yes, that is what I would suggest.

> previous i.MX system controller binding doc (fsl-imx-sc-wdt.txt) and add binding doc
> to (Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt) ?  
> 
I can't comment on that; I am neutral on how the documentation is
handled.

> > 
> > Additional comment below.
> > 
> > Guenter
> > 
> > > Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> > > ---
> > >   drivers/watchdog/Kconfig      |  1 +
> > >   drivers/watchdog/imx_sc_wdt.c | 65
> > +++++++++++++++++++++++++++++++++++++++----
> > >   2 files changed, 61 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig index
> > > 44a3158..f2c2c1a 100644
> > > --- a/drivers/watchdog/Kconfig
> > > +++ b/drivers/watchdog/Kconfig
> > > @@ -644,6 +644,7 @@ config IMX2_WDT
> > >   config IMX_SC_WDT
> > >   	tristate "IMX SC Watchdog"
> > >   	depends on HAVE_ARM_SMCCC
> > > +	depends on IMX_SCU
> > >   	select WATCHDOG_CORE
> > >   	help
> > >   	  This is the driver for the system controller watchdog diff --git
> > > a/drivers/watchdog/imx_sc_wdt.c b/drivers/watchdog/imx_sc_wdt.c index
> > > 49848b6..f45ed10 100644
> > > --- a/drivers/watchdog/imx_sc_wdt.c
> > > +++ b/drivers/watchdog/imx_sc_wdt.c
> > > @@ -4,6 +4,7 @@
> > >    */
> > >
> > >   #include <linux/arm-smccc.h>
> > > +#include <linux/firmware/imx/sci.h>
> > >   #include <linux/io.h>
> > >   #include <linux/init.h>
> > >   #include <linux/kernel.h>
> > > @@ -33,11 +34,16 @@
> > >
> > >   #define SC_TIMER_WDOG_ACTION_PARTITION	0
> > >
> > > +#define SC_IRQ_WDOG			1
> > > +#define SC_IRQ_GROUP_WDOG		1
> > > +
> > >   static bool nowayout = WATCHDOG_NOWAYOUT;
> > >   module_param(nowayout, bool, 0000);
> > >   MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once
> > started (default="
> > >   		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> > >
> > > +struct watchdog_device *imx_sc_wdd;
> > > +
> > >   static int imx_sc_wdt_ping(struct watchdog_device *wdog)
> > >   {
> > >   	struct arm_smccc_res res;
> > > @@ -85,12 +91,42 @@ static int imx_sc_wdt_set_timeout(struct
> > watchdog_device *wdog,
> > >   	return res.a0 ? -EACCES : 0;
> > >   }
> > >
> > > +static int imx_sc_wdt_set_pretimeout(struct watchdog_device *wdog,
> > > +				     unsigned int pretimeout)
> > > +{
> > > +	struct arm_smccc_res res;
> > > +
> > > +	wdog->pretimeout = pretimeout;
> > > +	arm_smccc_smc(IMX_SIP_TIMER,
> > IMX_SIP_TIMER_SET_PRETIME_WDOG,
> > > +		      pretimeout * 1000, 0, 0, 0, 0, 0, &res);
> > > +
> > > +	return res.a0 ? -EACCES : 0;
> > 
> > If this function returns an error, why does it set wdog->pretimeout
> > unconditionally ? That seems wrong.
> 
> You are right, I will fix it in V2, but looks like some other watchdog drivers also has such issue, such
> as below:
> 
> drivers/watchdog/pm8916_wdt.c
> drivers/watchdog/sprd_wdt.c
> 
You are correct, but that doesn't make this one better.

> > 
> > > +}
> > > +
> > > +static int imx_sc_wdt_notify(struct notifier_block *nb,
> > > +			     unsigned long event, void *group) {
> > > +	/* ignore other irqs */
> > > +	if (!(event & SC_IRQ_WDOG &&
> > > +		(*(u8 *)group == SC_IRQ_GROUP_WDOG)))
> > 
> > 	if (!(event & SC_IRQ_WDO) || *(u8 *)group !=
> > SC_IRQ_GROUP_WDOG)
> > 
> > would be easier to understand. Either case, the second part of the
> > expression has an unnecessary (), and multi-line alignment seems to be off.
> 
> Will improve it and fix the line alignment in V2.
> 
> > 
> > > +		return 0;
> > > +
> > > +	watchdog_notify_pretimeout(imx_sc_wdd);
> > 
> > The notifier block should be embedded in a local data structure, which would
> > include strict watchdog_device and struct notifier_block.
> > This would avoid the need for a static variable.
> 
> OK, I will add a local data structure to do it in V2.
> 
> > 
> > > +
> > > +	return 0;
> > 
> > If the function always returns 0, why not the following ?
> > Above code seems unnecessary complex for no good reason.
> > 
> > 	if (event & SC_IRQ_WDOG &&
> > 	    *(u8 *)group == SC_IRQ_GROUP_WDOG)
> > 		watchdog_notify_pretimeout(imx_sc_wdd);
> > 
> > 	return 0;
> 
> OK.
> 
> > 
> > > +}
> > > +
> > > +static struct notifier_block imx_sc_wdt_notifier = {
> > > +	.notifier_call = imx_sc_wdt_notify,
> > > +};
> > > +
> > >   static const struct watchdog_ops imx_sc_wdt_ops = {
> > >   	.owner = THIS_MODULE,
> > >   	.start = imx_sc_wdt_start,
> > >   	.stop  = imx_sc_wdt_stop,
> > >   	.ping  = imx_sc_wdt_ping,
> > >   	.set_timeout = imx_sc_wdt_set_timeout,
> > > +	.set_pretimeout = imx_sc_wdt_set_pretimeout,
> > >   };
> > >
> > >   static const struct watchdog_info imx_sc_wdt_info = { @@ -102,9
> > > +138,15 @@ static const struct watchdog_info imx_sc_wdt_info = {
> > >   static int imx_sc_wdt_probe(struct platform_device *pdev)
> > >   {
> > >   	struct device *dev = &pdev->dev;
> > > -	struct watchdog_device *imx_sc_wdd;
> > >   	int ret;
> > >
> > > +	/* wait until i.MX SCU IPC ready */
> > > +	ret = imx_scu_irq_group_enable(SC_IRQ_GROUP_WDOG,
> > > +				       SC_IRQ_WDOG,
> > > +				       true);
> > > +	if (ret == -EPROBE_DEFER)
> > > +		return ret;
> > > +
> > 
> > And if the error is anything else it is ignored ?
> > Also, what happens if the interrupt triggers before imx_sc_wdd is set ?
> 
> Other error ONLY means the IPC failed, the IRQ WDOG group will NOT be enabled,
> it does NOT impact other wdog functions, so I did NOT handle it, maybe I can add
> some warning message to tell user that pretimeout function is failed if other error
> occurs and also disable the pretimeout function in wdog info?
> 
Something like that, yes.

> If interrupt triggers before imx_sc_wdd is set, since the notifier is NOT registered yet,
> so the wdog interrupt will be ignored.  
> 
> > 
> > >   	imx_sc_wdd = devm_kzalloc(dev, sizeof(*imx_sc_wdd), GFP_KERNEL);
> > >   	if (!imx_sc_wdd)
> > >   		return -ENOMEM;
> > > @@ -117,6 +159,7 @@ static int imx_sc_wdt_probe(struct platform_device
> > *pdev)
> > >   	imx_sc_wdd->max_timeout = MAX_TIMEOUT;
> > >   	imx_sc_wdd->parent = dev;
> > >   	imx_sc_wdd->timeout = DEFAULT_TIMEOUT;
> > > +	imx_sc_wdd->pretimeout = 0;
> > 
> > Unnecessary.
> 
> OK.
> 
> > 
> > >
> > >   	watchdog_init_timeout(imx_sc_wdd, 0, dev);
> > >   	watchdog_stop_on_reboot(imx_sc_wdd);
> > > @@ -128,13 +171,26 @@ static int imx_sc_wdt_probe(struct
> > platform_device *pdev)
> > >   		return ret;
> > >   	}
> > >
> > > +	ret = imx_scu_irq_register_notifier(&imx_sc_wdt_notifier);
> > > +	if (ret)
> > > +		dev_warn(&pdev->dev,
> > > +			 "Failed to register watchdog irq notifier\n");
> > 
> > pretimeout support doesn't work in this case, and any claim to support it
> > seems inappropriate.
> 
> So how to disable pretimeout function in this case, just overwrite the watchdog_info
> to remove the WDIOF_PRETIMEOUT?
> 
Yes, though I don't recall seeing WDIOF_PRETIMEOUT to start with.

Guenter

> > 
> > > +
> > >   	return 0;
> > >   }
> > >
> > > -static int __maybe_unused imx_sc_wdt_suspend(struct device *dev)
> > > +static int imx_sc_wdt_remove(struct platform_device *pdev)
> > >   {
> > > -	struct watchdog_device *imx_sc_wdd = dev_get_drvdata(dev);
> > > +	imx_scu_irq_unregister_notifier(&imx_sc_wdt_notifier);
> > > +	imx_scu_irq_group_enable(SC_IRQ_GROUP_WDOG,
> > > +				 SC_IRQ_WDOG,
> > > +				 false);
> > >
> > I would prefer to see devm_add_action() calls.
> 
> Ah, agreed, will do it in V2.
> 
> Thanks,
> Anson.
> 
> > 
> > > +	return 0;
> > > +}
> > > +
> > > +static int __maybe_unused imx_sc_wdt_suspend(struct device *dev) {
> > >   	if (watchdog_active(imx_sc_wdd))
> > >   		imx_sc_wdt_stop(imx_sc_wdd);
> > >
> > > @@ -143,8 +199,6 @@ static int __maybe_unused
> > > imx_sc_wdt_suspend(struct device *dev)
> > >
> > >   static int __maybe_unused imx_sc_wdt_resume(struct device *dev)
> > >   {
> > > -	struct watchdog_device *imx_sc_wdd = dev_get_drvdata(dev);
> > > -
> > >   	if (watchdog_active(imx_sc_wdd))
> > >   		imx_sc_wdt_start(imx_sc_wdd);
> > >
> > > @@ -162,6 +216,7 @@ MODULE_DEVICE_TABLE(of, imx_sc_wdt_dt_ids);
> > >
> > >   static struct platform_driver imx_sc_wdt_driver = {
> > >   	.probe		= imx_sc_wdt_probe,
> > > +	.remove		= imx_sc_wdt_remove,
> > >   	.driver		= {
> > >   		.name	= "imx-sc-wdt",
> > >   		.of_match_table = imx_sc_wdt_dt_ids,
> > >
>