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

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Date:   Wed, 12 Jul 2023 06:40:43 +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 5/18/23 14:48, Dmitry Osipenko wrote:
> 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>

Benjamin, could you please add acks and review tags to the commits and
send v7? I'd also suggest to drop the "data->mode" checks unless there
is a good practical reason to keep them. There are no other drivers in
kernel that do such checks.

-- 
Best regards,
Dmitry