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Date: Sun, 4 Dec 2016 21:59:54 +0800
From: Yang Ling <gnaygnil@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Yang Ling <gnaygnil@...il.com>, Wim Van Sebroeck <wim@...ana.be>,
Keguang Zhang <keguang.zhang@...il.com>,
linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org,
linux-mips@...ux-mips.org
Subject: Re: [v2.1,1/2] watchdog: loongson1: Add Loongson1 SoC watchdog driver
On Thu, Nov 24, 2016 at 08:05:58AM -0800, Guenter Roeck wrote:
> On Fri, Oct 21, 2016 at 01:45:39PM +0800, Yang Ling wrote:
> > Add watchdog timer specific driver for Loongson1 SoC.
> >
> > Signed-off-by: Yang Ling <gnaygnil@...il.com>
>
> First of all, sorry for the late reply. I'll try to do better next time.
>
> > ---
> > V2.1 from Kelvin Cheung:
> > Use max_hw_heartbeat_ms instead of max_timeout.
> > V2:
> > Increase the value of the default heartbeat.
> > Modify the setup process for register.
> > Order include files and Makefile alphabetically.
> > V1.1:
> > Add a little debugging information.
> > ---
> > drivers/watchdog/Kconfig | 7 ++
> > drivers/watchdog/Makefile | 1 +
> > drivers/watchdog/loongson1_wdt.c | 158 +++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 166 insertions(+)
> > create mode 100644 drivers/watchdog/loongson1_wdt.c
> >
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index 50dbaa8..6707d43 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -1513,6 +1513,13 @@ config LANTIQ_WDT
> > help
> > Hardware driver for the Lantiq SoC Watchdog Timer.
> >
> > +config LOONGSON1_WDT
> > + tristate "Loongson1 SoC hardware watchdog"
> > + depends on MACH_LOONGSON32
> > + select WATCHDOG_CORE
> > + help
> > + Hardware driver for the Loongson1 SoC Watchdog Timer.
> > +
> > config RALINK_WDT
> > tristate "Ralink SoC watchdog"
> > select WATCHDOG_CORE
> > diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> > index cba0043..b6a8d70 100644
> > --- a/drivers/watchdog/Makefile
> > +++ b/drivers/watchdog/Makefile
> > @@ -157,6 +157,7 @@ obj-$(CONFIG_TXX9_WDT) += txx9wdt.o
> > obj-$(CONFIG_OCTEON_WDT) += octeon-wdt.o
> > octeon-wdt-y := octeon-wdt-main.o octeon-wdt-nmi.o
> > obj-$(CONFIG_LANTIQ_WDT) += lantiq_wdt.o
> > +obj-$(CONFIG_LOONGSON1_WDT) += loongson1_wdt.o
> > obj-$(CONFIG_RALINK_WDT) += rt2880_wdt.o
> > obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
> > obj-$(CONFIG_MT7621_WDT) += mt7621_wdt.o
> > diff --git a/drivers/watchdog/loongson1_wdt.c b/drivers/watchdog/loongson1_wdt.c
> > new file mode 100644
> > index 0000000..f885294
> > --- /dev/null
> > +++ b/drivers/watchdog/loongson1_wdt.c
> > @@ -0,0 +1,158 @@
> > +/*
> > + * Copyright (c) 2016 Yang Ling <gnaygnil@...il.com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms of the GNU General Public License as published by the
> > + * Free Software Foundation; either version 2 of the License, or (at your
> > + * option) any later version.
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/watchdog.h>
> > +#include <loongson1.h>
> > +
> > +#define DEFAULT_HEARTBEAT 30
> > +
> > +static bool nowayout = WATCHDOG_NOWAYOUT;
> > +module_param(nowayout, bool, 0444);
> > +
> > +static unsigned int heartbeat = DEFAULT_HEARTBEAT;
> > +module_param(heartbeat, uint, 0444);
> > +
> > +struct ls1x_wdt_drvdata {
> > + void __iomem *base;
> > + struct clk *clk;
> > + unsigned int counts_per_second;
> > + struct watchdog_device wdt;
> > +};
> > +
> > +static int ls1x_wdt_ping(struct watchdog_device *wdt_dev)
> > +{
> > + struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> > +
> > + writel(0x1, drvdata->base + WDT_SET);
> > +
> > + return 0;
> > +}
> > +
> > +static int ls1x_wdt_set_timeout(struct watchdog_device *wdt_dev,
> > + unsigned int timeout)
> > +{
> > + struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> > + unsigned int counts;
> > +
> > + wdt_dev->timeout = min(timeout, wdt_dev->max_hw_heartbeat_ms / 1000);
>
> wdt_dev->timeout needs to be set to the 'soft' timeout. The hardware timeout,
> if needed, needs to be saved internally (in struct ls1x_wdt_drvdata).
> Not that it is needed here, though - the value is not used elsewhere in the
> driver. So you can do something like
>
> wdt->timeout = timeout;
> timeout = min(timeout, wdt_dev->max_hw_heartbeat_ms / 1000);
> counts = drvdata->counts_per_second * timeout;
>
> > + counts = drvdata->counts_per_second * wdt_dev->timeout;
> > +
> > + writel(counts, drvdata->base + WDT_TIMER);
> > +
> > + return 0;
> > +}
> > +
> > +static int ls1x_wdt_start(struct watchdog_device *wdt_dev)
> > +{
> > + struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> > +
> > + writel(0x1, drvdata->base + WDT_EN);
> > +
> > + return 0;
> > +}
> > +
> > +static int ls1x_wdt_stop(struct watchdog_device *wdt_dev)
> > +{
> > + struct ls1x_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> > +
> > + writel(0x0, drvdata->base + WDT_EN);
> > +
> > + return 0;
> > +}
> > +
> > +static const struct watchdog_info ls1x_wdt_info = {
> > + .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
> > + .identity = "Loongson1 Watchdog",
> > +};
> > +
> > +static const struct watchdog_ops ls1x_wdt_ops = {
> > + .owner = THIS_MODULE,
> > + .start = ls1x_wdt_start,
> > + .stop = ls1x_wdt_stop,
> > + .ping = ls1x_wdt_ping,
> > + .set_timeout = ls1x_wdt_set_timeout,
> > +};
> > +
> > +static int ls1x_wdt_probe(struct platform_device *pdev)
> > +{
> > + struct ls1x_wdt_drvdata *drvdata;
> > + struct watchdog_device *ls1x_wdt;
> > + struct resource *res;
> > + int ret;
> > +
> > + drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
> > + if (!drvdata)
> > + return -ENOMEM;
> > +
> > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > + drvdata->base = devm_ioremap_resource(&pdev->dev, res);
> > + if (IS_ERR(drvdata->base))
> > + return PTR_ERR(drvdata->base);
> > +
> > + drvdata->clk = devm_clk_get(&pdev->dev, pdev->name);
> > + if (IS_ERR(drvdata->clk)) {
> > + dev_err(&pdev->dev, "failed to get %s clock\n", pdev->name);
>
> devm_clk_get() can return -EPROBE_DEFER, in which case you would not want
> an error message.
>
> > + return PTR_ERR(drvdata->clk);
> > + }
> > + clk_prepare_enable(drvdata->clk);
> > +
> > + drvdata->counts_per_second = clk_get_rate(drvdata->clk);
>
> clk_get_rate() can at least in theory return 0.
>
> > +
> > + ls1x_wdt = &drvdata->wdt;
> > + ls1x_wdt->info = &ls1x_wdt_info;
> > + ls1x_wdt->ops = &ls1x_wdt_ops;
> > + ls1x_wdt->min_timeout = 1;
> > + ls1x_wdt->max_hw_heartbeat_ms = U32_MAX / drvdata->counts_per_second *
> > + 1000;
> > + ls1x_wdt->parent = &pdev->dev;
> > +
> > + watchdog_init_timeout(ls1x_wdt, heartbeat, &pdev->dev);
>
> This has little practical effect. Problem is two-fold. First, the default
> heartbeat is not pre-set in ls1x_wdt. This means if the user specifies
> heartbeat=0 as module parameter, the timeout will be set to 0. Second,
> since heartbeat is -re-initialized, watchdog_init_timeout() will never fall
> back to devicetree data to initialize the timeout (maybe that doesn't matter
> for this architecture).
>
> In general it is better to set the default module parameter value to 0
> and initialize the timeout together with min_timeout and max_hw_heartbeat_ms.
>
> static unsigned int heartbeat;
> ...
> ls1x_wdt->timeout = DEFAULT_HEARTBEAT;
> ...
> watchdog_init_timeout(ls1x_wdt, heartbeat, &pdev->dev);
>
> > + watchdog_set_nowayout(ls1x_wdt, nowayout);
> > + watchdog_set_drvdata(ls1x_wdt, drvdata);
> > +
> > + ret = watchdog_register_device(&drvdata->wdt);
> > + if (ret < 0) {
> > + dev_err(&pdev->dev, "failed to register watchdog device\n");
> > + return ret;
> > + }
> > +
> > + platform_set_drvdata(pdev, drvdata);
> > +
> > + dev_info(&pdev->dev, "Loongson1 Watchdog driver registered\n");
> > +
> > + return 0;
> > +}
> > +
> > +static int ls1x_wdt_remove(struct platform_device *pdev)
> > +{
> > + struct ls1x_wdt_drvdata *drvdata = platform_get_drvdata(pdev);
> > +
> > + ls1x_wdt_stop(&drvdata->wdt);
> > + watchdog_unregister_device(&drvdata->wdt);
> > + clk_disable_unprepare(drvdata->clk);
> > +
> > + return 0;
> > +}
> > +
> > +static struct platform_driver ls1x_wdt_driver = {
> > + .probe = ls1x_wdt_probe,
> > + .remove = ls1x_wdt_remove,
> > + .driver = {
> > + .name = "ls1x-wdt",
> > + },
> > +};
> > +
> > +module_platform_driver(ls1x_wdt_driver);
> > +
> > +MODULE_AUTHOR("Yang Ling <gnaygnil@...il.com>");
> > +MODULE_DESCRIPTION("Loongson1 Watchdog Driver");
> > +MODULE_LICENSE("GPL");
Hi Guenter,
These will be fix in next release.
Thanks for your friendly reminder.
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