linux-kernel - Re: [PATCH v3 4/4] mfd: tps6586x: register restart handler

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Date:   Mon, 3 Apr 2023 01:30:09 +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:     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 v3 4/4] mfd: tps6586x: register restart handler

On 3/27/23 16:57, 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
> 8f0c714ad9be1ef774c98e8819a7a571451cb019.
> 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 (as not in use).
> 
> The TPS658629-Q1 (unfortunately the only TPS6586x with public data sheet)
> provides a SOFT RST bit in the SUPPLYENE reg to request a (cold) reboot.
> This avoids the hang-up.
> 
> Tested on a TPS658640.
> 
> Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
> ---
>  drivers/mfd/tps6586x.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/mfd/tps6586x.c b/drivers/mfd/tps6586x.c
> index 93f1bf440191..c8adf6a08277 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)
>  
> @@ -470,6 +471,17 @@ static int tps6586x_power_off_handler(struct sys_off_data *data)
>  	return tps6586x_set_bits(tps6586x_dev, TPS6586X_SUPPLYENE, SLEEP_MODE_BIT);
>  }
>  
> +static int tps6586x_restart_handler(struct sys_off_data *data)
> +{
> +	struct device *tps6586x_dev = data->cb_data;
> +
> +	/* bring pmic into HARD REBOOT state */
> +	tps6586x_set_bits(tps6586x_dev, TPS6586X_SUPPLYENE, SOFT_RST_BIT);
> +
> +	mdelay(500);
Is this delay needed? There is no delay in a case of power off.

-- 
Best regards,
Dmitry