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

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Message-ID: <590a4fb2-24b2-432b-92db-534c5a52ed0b@tuxon.dev>
Date: Mon, 2 Sep 2024 12:14:20 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Biju Das <biju.das.jz@...renesas.com>,
 Ulf Hansson <ulf.hansson@...aro.org>
Cc: "vkoul@...nel.org" <vkoul@...nel.org>,
 "kishon@...nel.org" <kishon@...nel.org>, "robh@...nel.org"
 <robh@...nel.org>, "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
 "geert+renesas@...der.be" <geert+renesas@...der.be>,
 "magnus.damm@...il.com" <magnus.damm@...il.com>,
 "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
 "mturquette@...libre.com" <mturquette@...libre.com>,
 "sboyd@...nel.org" <sboyd@...nel.org>,
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
 "linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
 "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 00/16] Add initial USB support for the Renesas RZ/G3S SoC



On 02.09.2024 11:53, Biju Das wrote:
> Hi Claudiu,
> 
>> -----Original Message-----
>> From: claudiu beznea <claudiu.beznea@...on.dev>
>> Sent: Monday, September 2, 2024 9:47 AM
>> Subject: Re: [PATCH 00/16] Add initial USB support for the Renesas RZ/G3S SoC
>>
>> Hi, Biju,
>>
>> On 02.09.2024 10:54, Biju Das wrote:
>>> Hi Claudiu,
>>>
>>>> -----Original Message-----
>>>> From: Biju Das
>>>> Sent: Saturday, August 31, 2024 6:14 AM
>>>> Subject: RE: [PATCH 00/16] Add initial USB support for the Renesas
>>>> RZ/G3S SoC
>>>>
>>>> Hi Claudiu,
>>>>
>>>>> -----Original Message-----
>>>>> From: claudiu beznea <claudiu.beznea@...on.dev>
>>>>> Sent: Friday, August 30, 2024 9:23 AM
>>>>> Subject: Re: [PATCH 00/16] Add initial USB support for the Renesas
>>>>> RZ/G3S SoC
>>>>>
>>>>> Hi, Ulf,
>>>>>
>>>>> On 29.08.2024 18:26, Ulf Hansson wrote:
>>>>>> On Thu, 22 Aug 2024 at 17:28, Claudiu <claudiu.beznea@...on.dev> wrote:
>>>>>>>
>>>>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Series adds initial USB support for the Renesas RZ/G3S SoC.
>>>>>>>
>>>>>>> Series is split as follows:
>>>>>>>
>>>>>>> - patch 01/16           - add clock reset and power domain support for USB
>>>>>>> - patch 02-04/16        - add reset control support for a USB signal
>>>>>>>                           that need to be controlled before/after
>>>>>>>                           the power to USB area is turned on/off.
>>>>>>>
>>>>>>>                           Philipp, Ulf, Geert, all,
>>>>>>>
>>>>>>>                           I detailed my approach for this in patch
>>>>>>>                           04/16, please have a look and let me know
>>>>>>>                           your input.
>>>>>>
>>>>>> I have looked briefly. Your suggested approach may work, but I have
>>>>>> a few thoughts, see below.
>>>>>>
>>>>>> If I understand correctly, it is the consumer driver for the device
>>>>>> that is attached to the USB power domain that becomes responsible
>>>>>> for asserting/de-asserting this new signal. Right?
>>>>>
>>>>> Right!
>>>>>
>>>>>>
>>>>>> In this regard, please note that the consumer driver doesn't really
>>>>>> know when the power domain really gets powered-on/off. Calling
>>>>>> pm_runtime_get|put*() is dealing with the reference counting. For
>>>>>> example, a call to pm_runtime_get*() just makes sure that the PM
>>>>>> domain gets-or-remains powered-on. Could this be a problem from the
>>>>>> reset-signal point of view?
>>>>>
>>>>> It should be safe. From the HW manual I understand the hardware
>>>>> block is something like the
>>>> following:
>>>>>
>>>>>
>>>>>                   USB area
>>>>>          +-------------------------+
>>>>>          |                         |
>>>>>          | PHY --->USB controller  |
>>>>> SYSC --> |  ^                      |
>>>>>          |  |                      |
>>>>>          | PHY reset               |
>>>>>          +-------------------------+
>>>>
>>>> How USB PWRRDY signal is connected to USB?
>>>>
>>>> USB block consists of PHY control, PHY, USB HOST and USB OTG Controller IPs.
>>>>
>>>> Is it connected to top level block or connected to each IP's for turning off the USB region power?
>>>>
>>>> ? Or Just PHY (HW manual mentions for AWO, the USB PWRRDY signal->USB PHY PWRRDY signal control)?
>>>
>>> As per the update from HW team,
>>>
>>> "SYS_USB_PWRRDY and SYS_PCIE_RST_RSM_B are used when transition from ALL_ON to AWO (or from AWO to
>> ALL_ON).
>>>
>>> Refer to step 8,9 in Table 41.10 Example Transition Flow Outline from ALL_ON Mode to AWO Mode.
>>> Refer to step 9,10 in Table 41.11 Example Transition Flow Outline from AWO Mode to ALL_ON Mode.
>>
>> All this is not new information.
>>
>> From experiments, we need to control these signals also when booting as intermediary booting
>> application may control and leave it in improper state. W/o having SYSC signals configured properly
>> there is no chance for USB to work (it should be the same for PCIe but I haven't explored it yet).
>>
>>>
>>> When turning off USB PHY and PCIe PHY, if they are not controlled, PHY may break."
>>
>> From experiments, I know this, as this is the reason the SYSC USB PWRRDY has been implemented in Linux
>> and proposed in this series.
> 
> You mean you call reset assert for USB PWRRDY signal for system transition (AWO Mode to ALL_ON Mode)??

reset assert on suspend, reset de-assert on resume.

And pm_runtime_put()/pm_runtime_resume_and_get() on the version where USB
PHYRDY is provided by SYSC as a PM domain. As I mentioned in the thread
with Ulf, this is something I explored locally.

All these are internal, not published in this version. This version just
adds initial bring-up support.

> 
> 
>  
>>>
>>> Do you have any plan to control this power transitions(ALL_ON to AWO and vice versa) in linux?
>>
>> As you know, the RZ/G3S USB PM code is already prepared. This is also configuring these signals when
>> going to suspend/exiting from resume. W/o configuring properly these signals the USB is not working
>> after a suspend/resume cycle.
> 
> One option is to handle SYSC USB PWRRDY signal in TF-A, if you plan to handle system transitions there??

As I mentioned, the settings in these registers may be changed by
intermediary booting applications. Depending on that, Linux need to control
it also on probe for USB to work (it should be the same with PCIe, these
signals seems similar from HW manual description).

Thank you,
Claudiu Beznea

> 
> Cheers,
> Biju
> 
> 
>