From: Guenter Roeck <linux@roeck-us.net>
To: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: wim@linux-watchdog.org, linux-watchdog@vger.kernel.org,
linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH v3] watchdog: renesas_wdt: Add a few cycles delay
Date: Fri, 7 Jun 2019 10:44:11 -0700 [thread overview]
Message-ID: <20190607174411.GA15497@roeck-us.net> (raw)
In-Reply-To: <1559711040-29779-1-git-send-email-yoshihiro.shimoda.uh@renesas.com>
[Note: I updated the subject to "PATCH v3"]
On Wed, Jun 05, 2019 at 02:04:00PM +0900, Yoshihiro Shimoda wrote:
> According to the hardware manual of R-Car Gen2 and Gen3,
> software should wait a few RLCK cycles as following:
> - Delay 2 cycles before setting watchdog counter.
> - Delay 3 cycles before disabling module clock.
>
> So, this patch adds such delays.
>
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
> ---
> Changes from v2 (https://patchwork.kernel.org/patch/10972721/):
> - Rename the wait function name.
> - Rename the variable name in the wait function.
> - Change variable type.
> - Add Wolfram-san and Niklas-san's Reviewed-by.
>
> Changes from v1 (https://patchwork.kernel.org/patch/10972641/):
> - Change formula to improve accuracy.
> - Add Geert-san's Reviewed-by.
>
> drivers/watchdog/renesas_wdt.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> index 565dbc1..0cfc0e9 100644
> --- a/drivers/watchdog/renesas_wdt.c
> +++ b/drivers/watchdog/renesas_wdt.c
> @@ -7,6 +7,7 @@
> */
> #include <linux/bitops.h>
> #include <linux/clk.h>
> +#include <linux/delay.h>
> #include <linux/io.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> @@ -70,6 +71,15 @@ static int rwdt_init_timeout(struct watchdog_device *wdev)
> return 0;
> }
>
> +static void rwdt_wait_cycles(struct rwdt_priv *priv, unsigned int cycles)
> +{
> + unsigned int delay;
> +
> + delay = DIV_ROUND_UP(cycles * 1000000, priv->clk_rate);
> +
> + usleep_range(delay, 2 * delay);
> +}
> +
> static int rwdt_start(struct watchdog_device *wdev)
> {
> struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
> @@ -80,6 +90,8 @@ static int rwdt_start(struct watchdog_device *wdev)
> /* Stop the timer before we modify any register */
> val = readb_relaxed(priv->base + RWTCSRA) & ~RWTCSRA_TME;
> rwdt_write(priv, val, RWTCSRA);
> + /* Delay 2 cycles before setting watchdog counter */
> + rwdt_wait_cycles(priv, 2);
>
> rwdt_init_timeout(wdev);
> rwdt_write(priv, priv->cks, RWTCSRA);
> @@ -98,6 +110,8 @@ static int rwdt_stop(struct watchdog_device *wdev)
> struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
>
> rwdt_write(priv, priv->cks, RWTCSRA);
> + /* Delay 3 cycles before disabling module clock */
> + rwdt_wait_cycles(priv, 3);
> pm_runtime_put(wdev->parent);
>
> return 0;
next prev parent reply other threads:[~2019-06-07 17:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-05 5:04 [PATCH] watchdog: renesas_wdt: Add a few cycles delay Yoshihiro Shimoda
2019-06-05 5:21 ` Yoshihiro Shimoda
2019-06-07 17:44 ` Guenter Roeck [this message]
2019-06-13 9:28 ` [PATCH v3] " Simon Horman
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