linux-kernel - Re: [PATCH v7 4/7] reset: rzg2l-usbphy-ctrl: Add support for USB PWRRDY

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Message-ID: <d0fa09bb-3e2c-478b-a9b1-af57254a4fb1@tuxon.dev>
Date: Wed, 8 Oct 2025 15:47:55 +0300
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Philipp Zabel <p.zabel@...gutronix.de>, vkoul@...nel.org,
 kishon@...nel.org, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 geert+renesas@...der.be, magnus.damm@...il.com,
 yoshihiro.shimoda.uh@...esas.com, biju.das.jz@...renesas.com
Cc: linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>
Subject: Re: [PATCH v7 4/7] reset: rzg2l-usbphy-ctrl: Add support for USB
 PWRRDY



On 10/8/25 15:16, Claudiu Beznea wrote:
> Hi, Philipp,
> 
> On 10/8/25 13:23, Philipp Zabel wrote:
>> Hi Claudiu,
>>
>> On Mi, 2025-10-08 at 12:29 +0300, Claudiu Beznea wrote:
>>> Hi, Philipp,
>>>
>>> On 10/8/25 11:34, Philipp Zabel wrote:
>>>> Hi Claudiu,
>>>>
>>>> On Do, 2025-09-25 at 13:02 +0300, Claudiu wrote:
>>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>>
>>>>> On the Renesas RZ/G3S SoC, the USB PHY block has an input signal called
>>>>> PWRRDY. This signal is managed by the system controller and must be
>>>>> de-asserted after powering on the area where USB PHY resides and asserted
>>>>> before powering it off.
>>>>>
>>>>> On power-on the USB PWRRDY signal need to be de-asserted before enabling
>>>>> clock and switching the module to normal state (through MSTOP support). The
>>>>> power-on configuration sequence
>>>>
>>>> The wording makes me wonder, have you considered implementing this as a
>>>> power sequencing driver?
>>>
>>> No, haven't tried as power sequencing. At the moment this was started I
>>> think the power sequencing support wasn't merged.
>>>
>>> The approaches considered were:
>>> a/ power domain
>>
>> Letting a power domain control a corresponding power ready signal would
>> have been my first instinct as well.
>>
>>> b/ regulator
>>> c/ as a reference counted bit done through regmap read/writes APIs
>>>
>>> a and b failed as a result of discussions in the previous posted versions.
>>
>> Could you point me to the discussion related to a?
> 
> It's this one
> https://lore.kernel.org/all/CAPDyKFrS4Dhd7DZa2zz=oPro1TiTJFix0awzzzp8Qatm-8Z2Ug@mail.gmail.com/
> 
> 
>>
>> I see v2 and v3 tried to control the bit from the PHY drivers, and in
>> v4 we were are already back to the reset driver.
> 
> v2 passed the system controller (SYSC) phandle to the USB PHYs only (though
> renesas,sysc-signals DT property) where the PWRRDY bit was set. The PWRRDY
> bit was referenced counted in the SYSC driver though regmap APIs.

Sorry, I forgot to mention: in v2, the SYSC phandle was passed to the PHYs
only as I wasn't aware of the block diagram presented in this patch
description. I got aware of the block diagram starting with v3.

Thank you,
Claudiu