Re: [PATCH v2 7/7] watchdog: imx93: add watchdog timer on imx93

[Guenter Roeck]

On Thu, Aug 25, 2022 at 04:32:56PM +0800, Alice Guo (OSS) wrote:
> From: Alice Guo <alice.guo@xxxxxxx>
> 
> The WDOG clocks are sourced from lpo_clk, and lpo_clk is the fixed
> 32KHz. TOVAL contains the 16-bit value used to set the timeout period of
> the watchdog. When the timeout period exceeds 2 seconds, the value
> written to the TOVAL register is larger than 16-bit can represent.
> Enabling watchdog prescaler can solve this problem.
> 
> Two points need to be aware of:
> 1. watchdog prescaler enables a fixed 256 pre-scaling of watchdog
> counter reference clock
> 2. reconfiguration takes about 55ms on imx93
> 
> Reviewed-by: Jacky Bai <ping.bai@xxxxxxx>
> Signed-off-by: Alice Guo <alice.guo@xxxxxxx>

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

> ---
> 
> Changes for v2:
>  - none
> 
>  drivers/watchdog/imx7ulp_wdt.c | 33 ++++++++++++++++++++++++++++-----
>  1 file changed, 28 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/imx7ulp_wdt.c b/drivers/watchdog/imx7ulp_wdt.c
> index dee02c2a52c9..2897902090b3 100644
> --- a/drivers/watchdog/imx7ulp_wdt.c
> +++ b/drivers/watchdog/imx7ulp_wdt.c
> @@ -9,6 +9,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/platform_device.h>
>  #include <linux/reboot.h>
>  #include <linux/watchdog.h>
> @@ -52,11 +53,17 @@ module_param(nowayout, bool, 0000);
>  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
>  		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>  
> +struct imx_wdt_hw_feature {
> +	bool prescaler_enable;
> +	u32 wdog_clock_rate;
> +};
> +
>  struct imx7ulp_wdt_device {
>  	struct watchdog_device wdd;
>  	void __iomem *base;
>  	struct clk *clk;
>  	bool post_rcs_wait;
> +	const struct imx_wdt_hw_feature *hw;
>  };
>  
>  static int imx7ulp_wdt_wait_ulk(void __iomem *base)
> @@ -179,7 +186,7 @@ static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog,
>  				   unsigned int timeout)
>  {
>  	struct imx7ulp_wdt_device *wdt = watchdog_get_drvdata(wdog);
> -	u32 toval = WDOG_CLOCK_RATE * timeout;
> +	u32 toval = wdt->hw->wdog_clock_rate * timeout;
>  	u32 val;
>  	int ret;
>  	u32 loop = RETRY_MAX;
> @@ -276,6 +283,9 @@ static int imx7ulp_wdt_init(struct imx7ulp_wdt_device *wdt, unsigned int timeout
>  	int ret;
>  	u32 loop = RETRY_MAX;
>  
> +	if (wdt->hw->prescaler_enable)
> +		val |= WDOG_CS_PRES;
> +
>  	do {
>  		ret = _imx7ulp_wdt_init(wdt, timeout, val);
>  		toval = readl(wdt->base + WDOG_TOVAL);
> @@ -346,7 +356,9 @@ 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);
> -	ret = imx7ulp_wdt_init(imx7ulp_wdt, wdog->timeout * WDOG_CLOCK_RATE);
> +
> +	imx7ulp_wdt->hw = of_device_get_match_data(dev);
> +	ret = imx7ulp_wdt_init(imx7ulp_wdt, wdog->timeout * imx7ulp_wdt->hw->wdog_clock_rate);
>  	if (ret)
>  		return ret;
>  
> @@ -368,7 +380,7 @@ static int __maybe_unused imx7ulp_wdt_suspend_noirq(struct device *dev)
>  static int __maybe_unused imx7ulp_wdt_resume_noirq(struct device *dev)
>  {
>  	struct imx7ulp_wdt_device *imx7ulp_wdt = dev_get_drvdata(dev);
> -	u32 timeout = imx7ulp_wdt->wdd.timeout * WDOG_CLOCK_RATE;
> +	u32 timeout = imx7ulp_wdt->wdd.timeout * imx7ulp_wdt->hw->wdog_clock_rate;
>  	int ret;
>  
>  	ret = clk_prepare_enable(imx7ulp_wdt->clk);
> @@ -389,9 +401,20 @@ static const struct dev_pm_ops imx7ulp_wdt_pm_ops = {
>  				      imx7ulp_wdt_resume_noirq)
>  };
>  
> +static const struct imx_wdt_hw_feature imx7ulp_wdt_hw = {
> +	.prescaler_enable = false,
> +	.wdog_clock_rate = 1000,
> +};
> +
> +static const struct imx_wdt_hw_feature imx93_wdt_hw = {
> +	.prescaler_enable = true,
> +	.wdog_clock_rate = 125,
> +};
> +
>  static const struct of_device_id imx7ulp_wdt_dt_ids[] = {
> -	{ .compatible = "fsl,imx8ulp-wdt", },
> -	{ .compatible = "fsl,imx7ulp-wdt", },
> +	{ .compatible = "fsl,imx8ulp-wdt", .data = &imx7ulp_wdt_hw, },
> +	{ .compatible = "fsl,imx7ulp-wdt", .data = &imx7ulp_wdt_hw, },
> +	{ .compatible = "fsl,imx93-wdt", .data = &imx93_wdt_hw, },
>  	{ /* sentinel */ }
>  };
>  MODULE_DEVICE_TABLE(of, imx7ulp_wdt_dt_ids);
> -- 
> 2.17.1
>