Re: [PATCH 00/16] Add initial USB support for the Renesas RZ/G3S SoC

[claudiu beznea <claudiu.beznea@tuxon.dev>]

On 03.09.2024 15:00, Biju Das wrote:
> 
> 
>> -----Original Message-----
>> From: Biju Das <biju.das.jz@bp.renesas.com>
>> Sent: Tuesday, September 3, 2024 12:07 PM
>> To: Claudiu.Beznea <claudiu.beznea@tuxon.dev>; Ulf Hansson <ulf.hansson@linaro.org>
>> Cc: vkoul@kernel.org; kishon@kernel.org; robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org;
>> p.zabel@pengutronix.de; geert+renesas@glider.be; magnus.damm@gmail.com; gregkh@linuxfoundation.org;
>> mturquette@baylibre.com; sboyd@kernel.org; Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>;
>> linux-phy@lists.infradead.org; devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
>> renesas-soc@vger.kernel.org; linux-usb@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
>> clk@vger.kernel.org; linux-pm@vger.kernel.org; Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>> Subject: RE: [PATCH 00/16] Add initial USB support for the Renesas RZ/G3S SoC
>>
>> Hi Claudiu,
>>
>>> -----Original Message-----
>>> From: claudiu beznea <claudiu.beznea@tuxon.dev>
>>> Sent: Tuesday, September 3, 2024 12:00 PM
>>> Subject: Re: [PATCH 00/16] Add initial USB support for the Renesas
>>> RZ/G3S SoC
>>>
>>>
>>>
>>> On 03.09.2024 13:31, Biju Das wrote:
>>>>>> During boot clr USB PWR READY signal in TF-A.
>>>>>> STR case, suspend set USB PWR READY signal in TF-A.
>>>>>> STR case, resume clr USB PWR READY signal in TF-A.
>>>>> As I said previously, it can be done in different ways. My point
>>>>> was to let Linux set what it needs for all it's devices to work. I
>>>>> think the way to go forward is a
>>> maintainer decision.
>>>>
>>>> I agree, there can be n number of solution for a problem.
>>>>
>>>> Since you modelled system state signal (USB PWRRDY) as reset control
>>>> signal, it is reset/DT maintainer's decision to say the final word
>>>> whether this signal fits in reset
>>> system framework or not?
>>>
>>> I was thinking:
>>> 1/ Geert would be the best to say if he considers it OK to handle this
>>>    in Linux
>>
>> I agree Geert is the right person for taking SYSTEM decisions, since the signal is used only during
>> state transitions (Table 41.6.4 AWO to ALL_ON and 41.6.3 ALL_ON to AWO)
> 
> One more info, as per [1], this USB PWRRDY signal setting to be before Linux kernel boots.

The "controlled by" column mentions CA-55 on PWRRDY signal control line and
it is b/w steps "DDR exits from retention mode" and  "clock start settings
for system bus and peripheral modules". AFAICT, after DDR exists retention
mode Linux is ready to run.

E.g. on resume Linux doesn't sets the clocks of all peripheral in sequence
and then runs the rest of settings for each peripheral, in turn it sets the
clock of one peripheral along with all the other necessary peripheral
settings and then continues with the rest of peripherals (including their
clocks).

> 
> All clocks/reset happens after setting USB PWRRDY signal
> 
> https://pasteboard.co/qbz021q7KPyi.png
> 
> Cheers,
> Biju