linux-kernel - Re: [BISECTED] Allwinner A33 tablet does not fully power off

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Message-ID: <a68b44f5-fd04-4dbe-0782-1d761c42ce3f@gmail.com>
Date:   Sat, 5 Nov 2022 10:23:36 +0200
From:   Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:     Samuel Holland <samuel@...lland.org>, wens@...e.org
Cc:     mripard@...nel.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Merlijn Wajer <merlijn@...zup.org>
Subject: Re: [BISECTED] Allwinner A33 tablet does not fully power off

Hi Samuel,

On 5.11.22 г. 4:21 ч., Samuel Holland wrote:
> Hi Ivo,
> 
> On 10/29/22 10:23, Ivaylo Dimitrov wrote:
>> After commit 843107498f91e57d1d4b22cd8787112726fdaeb4 (bus: sunxi-rsb:
>> Implement suspend/resume/shutdown callbacks) Q8 A33 tablet I have here
>> cannot be powered-on after power-off, it needs press-and-hold of the
>> power button for 10 seconds (I guess some HW assisted power down
>> happens) before it can be powered-on again.
>>
>> The following patch makes it behave correctly:
>>
>> diff --git a/drivers/bus/sunxi-rsb.c b/drivers/bus/sunxi-rsb.c
>> index 60b082fe2ed0..30016d62044c 100644
>> --- a/drivers/bus/sunxi-rsb.c
>> +++ b/drivers/bus/sunxi-rsb.c
>> @@ -818,10 +818,7 @@ static int sunxi_rsb_remove(struct platform_device
>> *pdev)
>>
>>   static void sunxi_rsb_shutdown(struct platform_device *pdev)
>>   {
>> -       struct sunxi_rsb *rsb = platform_get_drvdata(pdev);
>> -
>>          pm_runtime_disable(&pdev->dev);
>> -       sunxi_rsb_hw_exit(rsb);
>>   }
>>
>>   static const struct dev_pm_ops sunxi_rsb_dev_pm_ops = {
>>
>>
>> I guess the issue comes from the fact that by the time 'power off'
>> command to the power management IC has to be send, the bus it lives on
>> is already down, so the device is left in semi-powered down state. Ofc
>> this is a wild guess, however, preventing the bus being turned off on
>> shutdown fixes the issue.
> 
> Your guess is correct. The controller gets shut down in
> 
>    kernel_power_off()
>      kernel_shutdown_prepare()
>        device_shutdown()
> 
> but the PMIC communication needs to happen later in
> 
>    kernel_power_off()
>      machine_power_off()
>        pm_power_off()
> 
>> Please LMK if the above is the correct approach so I will send a proper
>> patch or something else shall be fixed.
> 
> Yes, this is exactly the right approach. The whole sunxi_rsb_shutdown()

Don't we need pm_runtime_disable() on shutdown? As IIUC, the controller 
might be suspended and we have to resume it to put it in state to accept 
commands later on(in pm_power_off()).

Regards,
Ivo

> function should be removed. When you send a patch, please add a Fixes:
> tag referencing the commit that you bisected to.
> 
> Regards,
> Samuel
>