linux-kernel - Re: [PATCH 2/2] watchdog: rzg2l_wdt: Handle TYPE-B reset for RZ/V2M

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Date:   Mon, 28 Nov 2022 20:54:31 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Biju Das <biju.das.jz@...renesas.com>,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        linux-renesas-soc@...r.kernel.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jacopo Mondi <jacopo@...ndi.org>
Subject: Re: [PATCH 2/2] watchdog: rzg2l_wdt: Handle TYPE-B reset for RZ/V2M

On 11/17/22 03:49, Fabrizio Castro wrote:
> As per section 48.4 of the HW User Manual, IPs in the RZ/V2M
> SoC need either a TYPE-A reset sequence or a TYPE-B reset
> sequence. More specifically, the watchdog IP needs a TYPE-B
> reset sequence.
> 
> If the proper reset sequence isn't implemented, then resetting
> IPs may lead to undesired behaviour. In the restart callback of
> the watchdog driver the reset has basically no effect on the
> desired funcionality, as the register writes following the reset
> happen before the IP manages to come out of reset.
> 
> Implement the TYPE-B reset sequence in the watchdog driver to
> address the issues with the restart callback on RZ/V2M.
> 
> Fixes: ec122fd94eeb ("watchdog: rzg2l_wdt: Add rzv2m support")
> Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   drivers/watchdog/rzg2l_wdt.c | 37 +++++++++++++++++++++++++++++++++++-
>   1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/rzg2l_wdt.c b/drivers/watchdog/rzg2l_wdt.c
> index ceca42db0837..d404953d0e0f 100644
> --- a/drivers/watchdog/rzg2l_wdt.c
> +++ b/drivers/watchdog/rzg2l_wdt.c
> @@ -8,6 +8,7 @@
>   #include <linux/clk.h>
>   #include <linux/delay.h>
>   #include <linux/io.h>
> +#include <linux/iopoll.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
>   #include <linux/of_device.h>
> @@ -35,6 +36,8 @@
>   
>   #define F2CYCLE_NSEC(f)			(1000000000 / (f))
>   
> +#define RZV2M_A_NSEC			730
> +
>   static bool nowayout = WATCHDOG_NOWAYOUT;
>   module_param(nowayout, bool, 0);
>   MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> @@ -51,11 +54,35 @@ struct rzg2l_wdt_priv {
>   	struct reset_control *rstc;
>   	unsigned long osc_clk_rate;
>   	unsigned long delay;
> +	unsigned long minimum_assertion_period;
>   	struct clk *pclk;
>   	struct clk *osc_clk;
>   	enum rz_wdt_type devtype;
>   };
>   
> +static int rzg2l_wdt_reset(struct rzg2l_wdt_priv *priv)
> +{
> +	int err, status;
> +
> +	if (priv->devtype == WDT_RZV2M) {
> +		/* WDT needs TYPE-B reset control */
> +		err = reset_control_assert(priv->rstc);
> +		if (err)
> +			return err;
> +		ndelay(priv->minimum_assertion_period);
> +		err = reset_control_deassert(priv->rstc);
> +		if (err)
> +			return err;
> +		err = read_poll_timeout(reset_control_status, status,
> +					status != 1, 0, 1000, false,
> +					priv->rstc);
> +	} else {
> +		err = reset_control_reset(priv->rstc);
> +	}
> +
> +	return err;
> +}
> +
>   static void rzg2l_wdt_wait_delay(struct rzg2l_wdt_priv *priv)
>   {
>   	/* delay timer when change the setting register */
> @@ -115,7 +142,7 @@ static int rzg2l_wdt_stop(struct watchdog_device *wdev)
>   {
>   	struct rzg2l_wdt_priv *priv = watchdog_get_drvdata(wdev);
>   
> -	reset_control_reset(priv->rstc);
> +	rzg2l_wdt_reset(priv);
>   	pm_runtime_put(wdev->parent);
>   
>   	return 0;
> @@ -154,6 +181,7 @@ static int rzg2l_wdt_restart(struct watchdog_device *wdev,
>   		rzg2l_wdt_write(priv, PEEN_FORCE, PEEN);
>   	} else {
>   		/* RZ/V2M doesn't have parity error registers */
> +		rzg2l_wdt_reset(priv);
>   
>   		wdev->timeout = 0;
>   
> @@ -251,6 +279,13 @@ static int rzg2l_wdt_probe(struct platform_device *pdev)
>   
>   	priv->devtype = (uintptr_t)of_device_get_match_data(dev);
>   
> +	if (priv->devtype == WDT_RZV2M) {
> +		priv->minimum_assertion_period = RZV2M_A_NSEC +
> +			3 * F2CYCLE_NSEC(pclk_rate) + 5 *
> +			max(F2CYCLE_NSEC(priv->osc_clk_rate),
> +			    F2CYCLE_NSEC(pclk_rate));
> +	}
> +
>   	pm_runtime_enable(&pdev->dev);
>   
>   	priv->wdev.info = &rzg2l_wdt_ident;