linux-kernel - Re: [PATCH v6 5/5] mfd: tps6586x: register restart handler

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Message-ID: <7eddaf8c-ab04-7670-fc45-15f0fce5eff2@collabora.com>
Date:   Thu, 18 May 2023 14:48:57 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Benjamin Bara <bbara93@...il.com>, Wolfram Sang <wsa@...nel.org>,
        Lee Jones <lee@...nel.org>, rafael.j.wysocki@...el.com
Cc:     peterz@...radead.org, jonathanh@...dia.com,
        richard.leitner@...ux.dev, treding@...dia.com,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        Benjamin Bara <benjamin.bara@...data.com>
Subject: Re: [PATCH v6 5/5] mfd: tps6586x: register restart handler

On 5/9/23 22:03, Benjamin Bara wrote:
> From: Benjamin Bara <benjamin.bara@...data.com>
> 
> There are a couple of boards which use a tps6586x as
> "ti,system-power-controller", e.g. the tegra20-tamonten.dtsi.
> For these, the only registered restart handler is the warm reboot via
> tegra's PMC. As the bootloader of the tegra20 requires the VDE, it must
> be ensured that VDE is enabled (which is the case after a cold reboot).
> For the "normal reboot", this is basically the case since 8f0c714ad9be.
> However, this workaround is not executed in case of an emergency restart.
> In case of an emergency restart, the system now simply hangs in the
> bootloader, as VDE is not enabled (because it is not used).
> 
> The TPS658629-Q1 provides a SOFT RST bit in the SUPPLYENE reg to request
> a (cold) reboot, which takes at least 20ms (as the data sheet states).
> This avoids the hang-up.
> 
> Tested on a TPS658640.
> 
> Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
> ---
>  drivers/mfd/tps6586x.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/mfd/tps6586x.c b/drivers/mfd/tps6586x.c
> index b12c9e18970a..3b8faa058e59 100644
> --- a/drivers/mfd/tps6586x.c
> +++ b/drivers/mfd/tps6586x.c
> @@ -30,6 +30,7 @@
>  #include <linux/mfd/tps6586x.h>
>  
>  #define TPS6586X_SUPPLYENE	0x14
> +#define SOFT_RST_BIT		BIT(0)
>  #define EXITSLREQ_BIT		BIT(1)
>  #define SLEEP_MODE_BIT		BIT(3)
>  
> @@ -475,6 +476,24 @@ static int tps6586x_power_off_handler(struct sys_off_data *data)
>  	return notifier_from_errno(-ETIME);
>  }
>  
> +static int tps6586x_restart_handler(struct sys_off_data *data)
> +{
> +	int ret;
> +
> +	/* TPS6586X only provides a hard/cold reboot, skip others. */
> +	if (data->mode != REBOOT_UNDEFINED && data->mode != REBOOT_COLD &&
> +	    data->mode != REBOOT_HARD)
> +		return NOTIFY_DONE;

Not sure whether it's worthwhile to care about the reboot mode. If we
would really care, then the supported modes should be a part of sys-off
handler definition. Maybe Rafael could comment on it.

Otherwise looks good.

Reviewed-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>

-- 
Best regards,
Dmitry