RE: [PATCH V5 1/2] watchdog: imx_sc: Add i.MX system controller watchdog support

[Anson Huang]

Hi, Guenter

Best Regards!
Anson Huang

> -----Original Message-----
> From: Guenter Roeck [mailto:groeck7@xxxxxxxxx] On Behalf Of Guenter
> Roeck
> Sent: 2019年3月4日 10:46
> To: Anson Huang <anson.huang@xxxxxxx>
> Cc: catalin.marinas@xxxxxxx; will.deacon@xxxxxxx; wim@linux-
> watchdog.org; shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx;
> kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; Andy Gross
> <andy.gross@xxxxxxxxxx>; heiko@xxxxxxxxx; horms+renesas@xxxxxxxxxxxx;
> arnd@xxxxxxxx; olof@xxxxxxxxx; bjorn.andersson@xxxxxxxxxx;
> jagan@xxxxxxxxxxxxxxxxxxxx; enric.balletbo@xxxxxxxxxxxxx;
> marc.w.gonzalez@xxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; dl-linux-imx
> <linux-imx@xxxxxxx>
> Subject: Re: [PATCH V5 1/2] watchdog: imx_sc: Add i.MX system controller
> watchdog support
> 
> On 3/3/19 5:32 PM, Anson Huang wrote:
> > Hi, Guenter
> >
> > Best Regards!
> > Anson Huang
> >
> >> -----Original Message-----
> >> From: Guenter Roeck [mailto:groeck7@xxxxxxxxx] On Behalf Of Guenter
> >> Roeck
> >> Sent: 2019年3月2日 2:32
> >> To: Anson Huang <anson.huang@xxxxxxx>
> >> Cc: catalin.marinas@xxxxxxx; will.deacon@xxxxxxx; wim@linux-
> >> watchdog.org; shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx;
> >> kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; Andy Gross
> >> <andy.gross@xxxxxxxxxx>; heiko@xxxxxxxxx;
> horms+renesas@xxxxxxxxxxxx;
> >> arnd@xxxxxxxx; olof@xxxxxxxxx; bjorn.andersson@xxxxxxxxxx;
> >> jagan@xxxxxxxxxxxxxxxxxxxx; enric.balletbo@xxxxxxxxxxxxx;
> >> marc.w.gonzalez@xxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> >> kernel@xxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; dl-linux-imx
> >> <linux-imx@xxxxxxx>
> >> Subject: Re: [PATCH V5 1/2] watchdog: imx_sc: Add i.MX system
> >> controller watchdog support
> >>
> >> On Fri, Mar 01, 2019 at 06:35:31AM +0000, Anson Huang wrote:
> >>> i.MX8QXP is an ARMv8 SoC which has a Cortex-M4 system controller
> >>> inside, the system controller is in charge of controlling power,
> >>> clock and watchdog etc..
> >>>
> >>> This patch adds i.MX system controller watchdog driver support,
> >>> watchdog operation needs to be done in secure EL3 mode via
> >>> ARM-Trusted-Firmware, using SMC call, CPU will trap into
> >>> ARM-Trusted-Firmware and then it will request system controller to
> >>> do watchdog operation via IPC.
> >>>
> >>> Signed-off-by: Anson Huang <Anson.Huang@xxxxxxx>
> >>> ---
> >>> Changes since V4:
> >>> 	- change the module build dependency as depends on IMX_SCU and
> >> HAVE_ARM_SMCCC, as this
> >>> 	  driver is ONLY for i.MX SoC with SCU inside and it uses ARM SMC call.
> >>> ---
> >>>   drivers/watchdog/Kconfig      |  14 +++
> >>>   drivers/watchdog/Makefile     |   1 +
> >>>   drivers/watchdog/imx_sc_wdt.c | 201
> >>> ++++++++++++++++++++++++++++++++++++++++++
> >>>   3 files changed, 216 insertions(+)
> >>>   create mode 100644 drivers/watchdog/imx_sc_wdt.c
> >>>
> >>> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> >>> index
> >>> 65c3c42..a6bfa54 100644
> >>> --- a/drivers/watchdog/Kconfig
> >>> +++ b/drivers/watchdog/Kconfig
> >>> @@ -625,6 +625,20 @@ config IMX2_WDT
> >>>   	  To compile this driver as a module, choose M here: the
> >>>   	  module will be called imx2_wdt.
> >>>
> >>> +config IMX_SC_WDT
> >>> +	tristate "IMX SC Watchdog"
> >>> +	depends on IMX_SCU
> >>> +	depends on HAVE_ARM_SMCCC
> >>> +	select WATCHDOG_CORE
> >>> +	help
> >>> +	  This is the driver for the system controller watchdog
> >>> +	  on the NXP i.MX SoCs with system controller inside.
> >>> +	  If you have one of these processors and wish to have
> >>> +	  watchdog support enabled, say Y, otherwise say N.
> >>> +
> >>> +	  To compile this driver as a module, choose M here: the
> >>> +	  module will be called imx_sc_wdt.
> >>> +
> >>>   config UX500_WATCHDOG
> >>>   	tristate "ST-Ericsson Ux500 watchdog"
> >>>   	depends on MFD_DB8500_PRCMU
> >>> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> >>> index 4e78a8c..0c9da63 100644
> >>> --- a/drivers/watchdog/Makefile
> >>> +++ b/drivers/watchdog/Makefile
> >>> @@ -68,6 +68,7 @@ obj-$(CONFIG_NUC900_WATCHDOG) +=
> >> nuc900_wdt.o
> >>>   obj-$(CONFIG_TS4800_WATCHDOG) += ts4800_wdt.o
> >>>   obj-$(CONFIG_TS72XX_WATCHDOG) += ts72xx_wdt.o
> >>>   obj-$(CONFIG_IMX2_WDT) += imx2_wdt.o
> >>> +obj-$(CONFIG_IMX_SC_WDT) += imx_sc_wdt.o
> >>>   obj-$(CONFIG_UX500_WATCHDOG) += ux500_wdt.o
> >>>   obj-$(CONFIG_RETU_WATCHDOG) += retu_wdt.o
> >>>   obj-$(CONFIG_BCM2835_WDT) += bcm2835_wdt.o diff --git
> >>> a/drivers/watchdog/imx_sc_wdt.c b/drivers/watchdog/imx_sc_wdt.c
> new
> >>> file mode 100644 index 0000000..50b49b2
> >>> --- /dev/null
> >>> +++ b/drivers/watchdog/imx_sc_wdt.c
> >>> @@ -0,0 +1,201 @@
> >>> +// SPDX-License-Identifier: GPL-2.0
> >>> +/*
> >>> + * Copyright 2018-2019 NXP.
> >>> + */
> >>> +
> >>> +#include <linux/arm-smccc.h>
> >>> +#include <linux/io.h>
> >>> +#include <linux/init.h>
> >>> +#include <linux/kernel.h>
> >>> +#include <linux/module.h>
> >>> +#include <linux/moduleparam.h>
> >>> +#include <linux/of.h>
> >>
> >> Should no longer be needed.
> >
> > Correct, I will remove it.
> >
> >>
> >>> +#include <linux/platform_device.h>
> >>> +#include <linux/reboot.h>
> >>> +#include <linux/watchdog.h>
> >>> +
> >>> +#define DEFAULT_TIMEOUT 60
> >>> +/*
> >>> + * Software timer tick implemented in scfw side, support 10ms to
> >>> +0xffffffff ms
> >>> + * in theory, but for normal case, 1s~128s is enough, you can
> >>> +change this max
> >>> + * value in case it's not enough.
> >>> + */
> >>> +#define MAX_TIMEOUT 128
> >>> +
> >>> +#define IMX_SIP_TIMER			0xC2000002
> >>> +#define IMX_SIP_TIMER_START_WDOG		0x01
> >>> +#define IMX_SIP_TIMER_STOP_WDOG		0x02
> >>> +#define IMX_SIP_TIMER_SET_WDOG_ACT	0x03
> >>> +#define IMX_SIP_TIMER_PING_WDOG		0x04
> >>> +#define IMX_SIP_TIMER_SET_TIMEOUT_WDOG	0x05
> >>> +#define IMX_SIP_TIMER_GET_WDOG_STAT	0x06
> >>> +#define IMX_SIP_TIMER_SET_PRETIME_WDOG	0x07
> >>> +
> >>> +#define SC_TIMER_WDOG_ACTION_PARTITION	0
> >>> +
> >>> +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) ")");
> >>> +
> >>> +static unsigned int timeout = DEFAULT_TIMEOUT;
> >>> +module_param(timeout, uint, 0000); MODULE_PARM_DESC(timeout,
> >>> +"Watchdog timeout in
> >> seconds
> >>> +(default="
> >>> +		 __MODULE_STRING(DEFAULT_TIMEOUT) ")");
> >>> +
> >>> +static struct platform_device *imx_sc_wdt_pdev;
> >>> +
> >>> +static int imx_sc_wdt_ping(struct watchdog_device *wdog) {
> >>> +	struct arm_smccc_res res;
> >>> +
> >>> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_PING_WDOG,
> >>> +		      0, 0, 0, 0, 0, 0, &res);
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static int imx_sc_wdt_start(struct watchdog_device *wdog) {
> >>> +	struct arm_smccc_res res;
> >>> +
> >>> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_START_WDOG,
> >>> +		      0, 0, 0, 0, 0, 0, &res);
> >>> +	if (res.a0)
> >>> +		return -EACCES;
> >>> +
> >>> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_SET_WDOG_ACT,
> >>> +		      SC_TIMER_WDOG_ACTION_PARTITION,
> >>> +		      0, 0, 0, 0, 0, &res);
> >>> +	return res.a0 ? -EACCES : 0;
> >>> +}
> >>> +
> >>> +static int imx_sc_wdt_stop(struct watchdog_device *wdog) {
> >>> +	struct arm_smccc_res res;
> >>> +
> >>> +	arm_smccc_smc(IMX_SIP_TIMER, IMX_SIP_TIMER_STOP_WDOG,
> >>> +		      0, 0, 0, 0, 0, 0, &res);
> >>> +
> >>> +	return res.a0 ? -EACCES : 0;
> >>> +}
> >>> +
> >>> +static int imx_sc_wdt_set_timeout(struct watchdog_device *wdog,
> >>> +				unsigned int timeout)
> >>> +{
> >>> +	struct arm_smccc_res res;
> >>> +
> >>> +	wdog->timeout = timeout;
> >>> +	arm_smccc_smc(IMX_SIP_TIMER,
> >> IMX_SIP_TIMER_SET_TIMEOUT_WDOG,
> >>> +		      timeout * 1000, 0, 0, 0, 0, 0, &res);
> >>> +
> >>> +	return res.a0 ? -EACCES : 0;
> >>> +}
> >>> +
> >>> +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, };
> >>> +
> >>> +static const struct watchdog_info imx_sc_wdt_info = {
> >>> +	.identity	= "i.MX SC watchdog timer",
> >>> +	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
> >>> +			  WDIOF_MAGICCLOSE | WDIOF_PRETIMEOUT, };
> >>> +
> >>> +static int imx_sc_wdt_probe(struct platform_device *pdev) {
> >>> +	struct watchdog_device *imx_sc_wdd;
> >>> +	int ret;
> >>> +
> >>> +	imx_sc_wdd = devm_kzalloc(&pdev->dev, sizeof(*imx_sc_wdd),
> >> GFP_KERNEL);
> >>> +	if (!imx_sc_wdd)
> >>> +		return -ENOMEM;
> >>> +
> >>> +	platform_set_drvdata(pdev, imx_sc_wdd);
> >>> +
> >>> +	imx_sc_wdd->info = &imx_sc_wdt_info;
> >>> +	imx_sc_wdd->ops = &imx_sc_wdt_ops;
> >>> +	imx_sc_wdd->min_timeout = 1;
> >>> +	imx_sc_wdd->max_timeout = MAX_TIMEOUT;
> >>> +	imx_sc_wdd->parent = &pdev->dev;
> >>> +	imx_sc_wdd->timeout = DEFAULT_TIMEOUT;
> >>> +
> >>> +	ret = watchdog_init_timeout(imx_sc_wdd, timeout, &pdev->dev);
> >>> +	if (ret)
> >>> +		dev_warn(&pdev->dev, "Failed to set timeout value, using
> >>> +default\n");
> >>> +
> >>> +	watchdog_stop_on_reboot(imx_sc_wdd);
> >>> +	watchdog_stop_on_unregister(imx_sc_wdd);
> >>> +
> >>> +	ret = devm_watchdog_register_device(&pdev->dev, imx_sc_wdd);
> >>> +	if (ret) {
> >>> +		dev_err(&pdev->dev, "Failed to register watchdog device\n");
> >>> +		return ret;
> >>> +	}
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static int __maybe_unused imx_sc_wdt_suspend(struct device *dev) {
> >>> +	struct watchdog_device *imx_sc_wdd = dev_get_drvdata(dev);
> >>> +
> >>> +	if (watchdog_active(imx_sc_wdd))
> >>> +		imx_sc_wdt_stop(imx_sc_wdd);
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +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);
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static SIMPLE_DEV_PM_OPS(imx_sc_wdt_pm_ops,
> >>> +			 imx_sc_wdt_suspend, imx_sc_wdt_resume);
> >>> +
> >>> +static struct platform_driver imx_sc_wdt_driver = {
> >>> +	.probe		= imx_sc_wdt_probe,
> >>> +	.driver		= {
> >>> +		.name	= "imx-sc-wdt",
> >>> +		.pm	= &imx_sc_wdt_pm_ops,
> >>> +	},
> >>> +};
> >>> +
> >>> +static int __init imx_sc_wdt_init(void) {
> >>> +	int ret;
> >>> +
> >>> +	ret = platform_driver_register(&imx_sc_wdt_driver);
> >>> +	if (ret)
> >>> +		return ret;
> >>> +
> >>> +	imx_sc_wdt_pdev = platform_device_register_simple("imx-sc-wdt", -
> >> 1, NULL, 0);
> >>> +	if (IS_ERR(imx_sc_wdt_pdev)) {
> >>> +		platform_driver_unregister(&imx_sc_wdt_driver);
> >>> +		return PTR_ERR(imx_sc_wdt_pdev);
> >>> +	}
> >>
> >> I just realized what you are doing here. So the watchdog will always
> >> be instantiated if/when the module is loaded. I don't think that was
> >> the idea, and it seems to be risky. What happens if someone loads the
> >> module on a system where the watchdog is not supported ? There maye
> >> be lots of "Access Denied" errors, or something undefined may happen.
> >
> > I thought the "depends on IMX_SCU" was already added in Kconfig, that
> > means the module will be ONLY built with IMX_SCU enabled, and watchdog
> > will be always enabled if IMX_SCU is enabled. Is it safe enough?
> >
> No. The driver will be built with arm64:defconfig, meaning it will be built for
> all arm64 systems using defconfig. Any such system will have the driver
> installed as module, and nothing will prevent the user from running
> modprobe. But even if it wasn't enabled with defconfig, we must not
> instantiate the driver on an arbitrary system.
> 
> >>
> >> Is everyone on Cc: ok with this ? Is this how we handle
> >> instantiations nowadays ?  Or should the driver be instantiated from
> >> imx_scu_probe() in drivers/firmware/imx/imx-scu.c ?
> >>
> >> Sorry if the answer is obvious, but I am still struggling with "no
> >> more instantiations through devicetree".
> >>
> >> If the driver is auto-instantiated when the module is loaded, as
> >> currently written, there needs to be some check if it is actually
> >> supported, possibly in
> >> imx_sc_wdt_init() or, if that is not possible, in the probe function.
> >> I don't like that, but it would at least prevent the module from
> >> being loaded when the hardware is not supported.
> >
> > Other modules depend on the IMX_SCU IPC will have defer probe there to
> > make sure IMX_SCU driver is ready for IPC handle, since watchdog
> > driver ONLY uses ARM SMC but no IPC call, so I did NOT add the defer
> > probe handle here, so if adding it can answer your question/concern,
> > then I can add it, although I think the dependency in Kconfig should
> > be good here. Without SCU firmware ready, the SoC does NOT boot up A
> core with ATF/Linux at all.
> >
> That has nothing to do with deferred probing. My concern is that the driver
> will be instantiated just by loading it, no matter if the hardware supporting it
> is present or not.
> 
> Having a devicetree node would have prevented that since it instantiates the
> child drivers with devm_of_platform_populate() in imx_scu_probe(). The
> equivalent is to register the platform device from imx_scu_probe().
> That is the only means to prevent the driver from being instantiated where it
> shouldn't. As mentioned before, I would have preferred the devicetree
> method, but having it no longer available doesn't mean that we should add
> risky code.
> 
> Maybe you can check in the init function if the 'fsl,imx-scu' node exists, and
> instantiate the driver if it does. I don't like that either, but it would be
> acceptable to me - and maybe better than instantiating it manually from
> imx_scu_probe().

OK, I can add check of "fsl,imx-scu" in init function and ONLY instantiate the driver if
it exist, since there is no watchdog node in devicetree and "fsl,imx-scu" should be treated
as watchdog node, so adding such check also makes some sense, putting it inside SCU
driver is NOT that good I think, do you agree?

Anson.

> 
> Guenter
> 
> > Thanks,
> > Anson.
> >
> > RTC:
> >   68 static int imx_sc_rtc_probe(struct platform_device *pdev)
> >   69 {
> >   70         int ret;
> >   71
> >   72         ret = imx_scu_get_handle(&rtc_ipc_handle);
> >   73         if (ret)
> >   74                 return ret;
> >
> > SCU:
> >   92 int imx_scu_get_handle(struct imx_sc_ipc **ipc)
> >   93 {
> >   94         if (!imx_sc_ipc_handle)
> >   95                 return -EPROBE_DEFER;
> >   96
> >   97         *ipc = imx_sc_ipc_handle;
> >   98         return 0;
> >   99 }
> > 100 EXPORT_SYMBOL(imx_scu_get_handle);
> >
> >>
> >> Guenter
> >>
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +module_init(imx_sc_wdt_init);
> >>> +
> >>> +static void __exit imx_sc_wdt_exit(void) {
> >>> +	platform_driver_unregister(&imx_sc_wdt_driver);
> >>> +	platform_device_unregister(imx_sc_wdt_pdev);
> >>> +}
> >>> +module_exit(imx_sc_wdt_exit);
> >>> +
> >>> +MODULE_AUTHOR("Robin Gong <yibin.gong@xxxxxxx>");
> >>> +MODULE_DESCRIPTION("NXP i.MX system controller watchdog driver");
> >>> +MODULE_LICENSE("GPL v2");
> >>> --
> >>> 2.7.4
> >>>