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

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Message-ID:
 <TY3PR01MB11346505565B81AD2894E035586922@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 2 Sep 2024 09:18:34 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Claudiu.Beznea <claudiu.beznea@...on.dev>, Ulf Hansson
	<ulf.hansson@...aro.org>
CC: "vkoul@...nel.org" <vkoul@...nel.org>, "kishon@...nel.org"
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 Shimoda <yoshihiro.shimoda.uh@...esas.com>, "linux-phy@...ts.infradead.org"
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	<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

Hi Claudiu,

> -----Original Message-----
> From: claudiu beznea <claudiu.beznea@...on.dev>
> Sent: Monday, September 2, 2024 10:14 AM
> 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).

You mean system transition settings will be override by U-boot, so Linux needs to restore it back??

Cheers,
Biju