linux-kernel - Re: [PATCH 2/4] usb: host: ehci-platform: Call reset assert/deassert on suspend/resume

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Message-ID: <64c74f86-7438-49da-b164-a8a113e47c32@tuxon.dev>
Date: Thu, 6 Nov 2025 16:59:02 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: stern@...land.harvard.edu, gregkh@...uxfoundation.org,
 p.zabel@...gutronix.de, yoshihiro.shimoda.uh@...esas.com,
 prabhakar.mahadev-lad.rj@...renesas.com, kuninori.morimoto.gx@...esas.com,
 geert+renesas@...der.be, linux-usb@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 2/4] usb: host: ehci-platform: Call reset assert/deassert
 on suspend/resume

Hi, Geert,

On 11/6/25 16:52, Geert Uytterhoeven wrote:
> Hi Claudiu,
> 
> On Thu, 6 Nov 2025 at 15:36, Claudiu <claudiu.beznea@...on.dev> wrote:
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> The Renesas RZ/G3S SoC supports a power-saving mode in which power to most
>> of the SoC components is turned off, including the USB blocks. On the
>> resume path, the reset signal must be de-asserted before applying any
>> settings to the USB registers. To handle this properly, call
>> reset_control_assert() and reset_control_deassert() during suspend and
>> resume, respectively.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> 
> Thanks for your patch!
> 
>> --- a/drivers/usb/host/ehci-platform.c
>> +++ b/drivers/usb/host/ehci-platform.c
>> @@ -454,6 +454,17 @@ static int __maybe_unused ehci_platform_suspend(struct device *dev)
>>         if (pdata->power_suspend)
>>                 pdata->power_suspend(pdev);
>>
>> +       ret = reset_control_assert(priv->rsts);
>> +       if (ret) {
>> +               if (pdata->power_on)
>> +                       pdata->power_on(pdev);
>> +
>> +               ehci_resume(hcd, false);
>> +
>> +               if (priv->quirk_poll)
>> +                       quirk_poll_init(priv);
> 
> I have my doubts about the effectiveness of this "reverse error
> handling".  If the reset_control_assert() failed, what are the chances
> that the device will actually work after trying to bring it up again?
> 
> Same comment for next patch.

I wasn't sure if I should do this revert or not. In my mind, if the reset
assert fails, the reset signal is still de-asserted.

Thank you,
Claudiu

> 
>> +       }
>> +
>>         return ret;
>>  }
>>
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>