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Message-ID: <20200730165240.GA178323@roeck-us.net>
Date: Thu, 30 Jul 2020 09:52:40 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Anson Huang <Anson.Huang@....com>
Cc: wim@...ux-watchdog.org, shawnguo@...nel.org,
s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
linux-watchdog@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Linux-imx@....com
Subject: Re: [PATCH V3 1/2] watchdog: imx7ulp: Strictly follow the sequence
for wdog operations
On Thu, Jul 30, 2020 at 10:03:10AM +0800, Anson Huang wrote:
> According to reference manual, the i.MX7ULP WDOG's operations except
> refresh should follow below sequence:
>
> 1. disable global interrupts;
> 2. unlock the wdog and wait unlock bit set;
> 3. reconfigure the wdog and wait for reconfiguration bit set;
> 4. enabel global interrupts.
>
> Strictly follow the recommended sequence can make it more robust.
>
> Signed-off-by: Anson Huang <Anson.Huang@....com>
> ---
> changes since V2:
> - change the wait timeout to 20us according to experiment;
> - drop WARN_ON when timeout, and check its return value in each caller for
> unlock wait, no need to handle the return value for reconfiguration.
> ---
> drivers/watchdog/imx7ulp_wdt.c | 74 ++++++++++++++++++++++++++++++++++--------
> 1 file changed, 61 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/watchdog/imx7ulp_wdt.c b/drivers/watchdog/imx7ulp_wdt.c
> index 7993c8c..010ddd1 100644
> --- a/drivers/watchdog/imx7ulp_wdt.c
> +++ b/drivers/watchdog/imx7ulp_wdt.c
> @@ -5,6 +5,7 @@
>
> #include <linux/clk.h>
> #include <linux/io.h>
> +#include <linux/iopoll.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/of.h>
> @@ -36,6 +37,7 @@
> #define DEFAULT_TIMEOUT 60
> #define MAX_TIMEOUT 128
> #define WDOG_CLOCK_RATE 1000
> +#define WDOG_WAIT_TIMEOUT 20
>
> static bool nowayout = WATCHDOG_NOWAYOUT;
> module_param(nowayout, bool, 0000);
> @@ -48,17 +50,40 @@ struct imx7ulp_wdt_device {
> struct clk *clk;
> };
>
> -static void imx7ulp_wdt_enable(struct watchdog_device *wdog, bool enable)
> +static int imx7ulp_wdt_wait(void __iomem *base, u32 mask)
> +{
> + u32 val = readl(base + WDOG_CS);
> +
> + if (!(val & mask) && readl_poll_timeout_atomic(base + WDOG_CS, val,
> + val & mask, 0,
> + WDOG_WAIT_TIMEOUT))
> + return -ETIMEDOUT;
> +
> + return 0;
> +}
> +
> +static int imx7ulp_wdt_enable(struct watchdog_device *wdog, bool enable)
> {
> struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
>
> u32 val = readl(wdt->base + WDOG_CS);
> + int ret;
>
> + local_irq_disable();
> writel(UNLOCK, wdt->base + WDOG_CNT);
> + ret = imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK);
> + if (ret)
> + goto enable_out;
> if (enable)
> writel(val | WDOG_CS_EN, wdt->base + WDOG_CS);
> else
> writel(val & ~WDOG_CS_EN, wdt->base + WDOG_CS);
> + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS);
> +
> +enable_out:
> + local_irq_enable();
> +
> + return ret;
> }
>
> static bool imx7ulp_wdt_is_enabled(void __iomem *base)
> @@ -79,17 +104,12 @@ static int imx7ulp_wdt_ping(struct watchdog_device *wdog)
>
> static int imx7ulp_wdt_start(struct watchdog_device *wdog)
> {
> -
> - imx7ulp_wdt_enable(wdog, true);
> -
> - return 0;
> + return imx7ulp_wdt_enable(wdog, true);
> }
>
> static int imx7ulp_wdt_stop(struct watchdog_device *wdog)
> {
> - imx7ulp_wdt_enable(wdog, false);
> -
> - return 0;
> + return imx7ulp_wdt_enable(wdog, false);
> }
>
> static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog,
> @@ -97,22 +117,37 @@ static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog,
> {
> struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
> u32 val = WDOG_CLOCK_RATE * timeout;
> + int ret;
>
> + local_irq_disable();
> writel(UNLOCK, wdt->base + WDOG_CNT);
> + ret = imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK);
> + if (ret)
> + goto timeout_out;
> writel(val, wdt->base + WDOG_TOVAL);
> + imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS);
> +
> +timeout_out:
> + local_irq_enable();
>
> wdog->timeout = timeout;
This needs to be moved up - the timeout did not get changed on error.
Guenter
>
> - return 0;
> + return ret;
> }
>
> static int imx7ulp_wdt_restart(struct watchdog_device *wdog,
> unsigned long action, void *data)
> {
> struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
> + int ret;
> +
> + ret = imx7ulp_wdt_enable(wdog, true);
> + if (ret)
> + return ret;
>
> - imx7ulp_wdt_enable(wdog, true);
> - imx7ulp_wdt_set_timeout(&wdt->wdd, 1);
> + ret = imx7ulp_wdt_set_timeout(&wdt->wdd, 1);
> + if (ret)
> + return ret;
>
> /* wait for wdog to fire */
> while (true)
> @@ -136,19 +171,30 @@ static const struct watchdog_info imx7ulp_wdt_info = {
> WDIOF_MAGICCLOSE,
> };
>
> -static void imx7ulp_wdt_init(void __iomem *base, unsigned int timeout)
> +static int imx7ulp_wdt_init(void __iomem *base, unsigned int timeout)
> {
> u32 val;
> + int ret;
>
> + local_irq_disable();
> /* unlock the wdog for reconfiguration */
> writel_relaxed(UNLOCK_SEQ0, base + WDOG_CNT);
> writel_relaxed(UNLOCK_SEQ1, base + WDOG_CNT);
> + ret = imx7ulp_wdt_wait(base, WDOG_CS_ULK);
> + if (ret)
> + goto init_out;
>
> /* set an initial timeout value in TOVAL */
> writel(timeout, base + WDOG_TOVAL);
> /* enable 32bit command sequence and reconfigure */
> val = WDOG_CS_CMD32EN | WDOG_CS_CLK | WDOG_CS_UPDATE;
> writel(val, base + WDOG_CS);
> + imx7ulp_wdt_wait(base, WDOG_CS_RCS);
> +
> +init_out:
> + local_irq_enable();
> +
> + return ret;
> }
>
> static void imx7ulp_wdt_action(void *data)
> @@ -199,7 +245,9 @@ static int imx7ulp_wdt_probe(struct platform_device *pdev)
> watchdog_stop_on_reboot(wdog);
> watchdog_stop_on_unregister(wdog);
> watchdog_set_drvdata(wdog, imx7ulp_wdt);
> - imx7ulp_wdt_init(imx7ulp_wdt->base, wdog->timeout * WDOG_CLOCK_RATE);
> + ret = imx7ulp_wdt_init(imx7ulp_wdt->base, wdog->timeout * WDOG_CLOCK_RATE);
> + if (ret)
> + return ret;
>
> return devm_watchdog_register_device(dev, wdog);
> }
> --
> 2.7.4
>
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