linux-kernel - Re: [PATCH v5 6/6] mfd: tps6586x: register restart handler

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Message-ID: <20230420140406.GH996918@google.com>
Date:   Thu, 20 Apr 2023 15:04:06 +0100
From:   Lee Jones <lee@...nel.org>
To:     Benjamin Bara <bbara93@...il.com>
Cc:     Wolfram Sang <wsa@...nel.org>, rafael.j.wysocki@...el.com,
        dmitry.osipenko@...labora.com, 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 v5 6/6] mfd: tps6586x: register restart handler

On Tue, 18 Apr 2023, 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 (unfortunately the only TPS6586x with public data sheet)
> provides a SOFT RST bit in the SUPPLYENE reg to request a (cold) reboot,
> which takes at least 10ms (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 226e856e34e0..f7665b368071 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. */

TPS6586x

> +	if (data->mode != REBOOT_UNDEFINED && data->mode != REBOOT_COLD &&
> +	    data->mode != REBOOT_HARD)
> +		return NOTIFY_DONE;
> +
> +	/* bring pmic into HARD REBOOT state. this takes at least 10ms. */

Same as the other patch.

> +	ret = tps6586x_set_bits(data->dev, TPS6586X_SUPPLYENE, SOFT_RST_BIT);
> +	if (ret)
> +		return notifier_from_errno(ret);
> +
> +	mdelay(20);

Why 20 here and 50 in the other patch?

> +	return notifier_from_errno(-ETIME);
> +}
> +
>  static void tps6586x_print_version(struct i2c_client *client, int version)
>  {
>  	const char *name;
> @@ -575,6 +594,13 @@ static int tps6586x_i2c_probe(struct i2c_client *client)
>  			dev_err(&client->dev, "register power off handler failed: %d\n", ret);
>  			goto err_add_devs;
>  		}
> +
> +		ret = devm_register_restart_handler(&client->dev, &tps6586x_restart_handler,
> +						    NULL);
> +		if (ret) {
> +			dev_err(&client->dev, "register restart handler failed: %d\n", ret);
> +			goto err_add_devs;
> +		}
>  	}
>  
>  	return 0;
> 
> -- 
> 2.34.1
> 

-- 
Lee Jones [李琼斯]