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

[claudiu beznea]

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 at tuxon.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 at tuxon.dev> wrote:
>>>>>
>>>>> From: Claudiu Beznea <claudiu.beznea.uj at bp.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.

> 
> 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.

Thank you,
Claudiu Beznea


> Cheers,
> Biju
>