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

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Message-ID:
 <TY3PR01MB113464D53083F4C8A5DBBA36586922@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 2 Sep 2024 08:53:37 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Claudiu.Beznea <claudiu.beznea@...on.dev>, Ulf Hansson
	<ulf.hansson@...aro.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 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)??


 
> >
> > 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??

Cheers,
Biju