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

[Philipp Zabel <p.zabel@pengutronix.de>]

Hi Claudiu,

On Do, 2024-11-07 at 12:00 +0200, Claudiu Beznea wrote:
> Hi, all,
> 
> On 03.09.2024 17:48, claudiu beznea wrote:
> > 
> > 
> > On 03.09.2024 16:45, Biju Das wrote:
> > > Hi Claudiu,
> > > 
> > > > -----Original Message-----
> > > > From: claudiu beznea <claudiu.beznea@tuxon.dev>
> > > > Sent: Tuesday, September 3, 2024 1:57 PM
> > > > Subject: Re: [PATCH 00/16] Add initial USB support for the Renesas RZ/G3S SoC
> > > > 
> > > > 
> > > > 
> > > > On 03.09.2024 15:37, Biju Das wrote:
> > > > > 
> > > > > 
> > > > > > -----Original Message-----
> > > > > > From: claudiu beznea <claudiu.beznea@tuxon.dev>
> > > > > > Sent: Tuesday, September 3, 2024 1:26 PM
> > > > > > To: Biju Das <biju.das.jz@bp.renesas.com>; 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
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > 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.
> > > > > 
> > > > > DDR retention exit happens in TF-A and it jumps into reset code where it executes BL2 in TF_A. Bl2
> > > > checks for warm or cold reset.
> > > > > If it is warm reset, it sets required minimal clocks/resets and pass
> > > > > the control to linux by calling the SMC callback handler. Which in turn calls resume(step 11-->14)
> > > > path.
> > > > 
> > > > Is this from HW manual or some specific documentation? I'm referring at "resume" == "steps 11-->14"
> > > > 
> > > > > 
> > > > > Step 8, Cortex-A55 Exit from DDR retention mode (when using) Setting
> > > > > for exiting form DDR retention mode Step 9, Cortex-A55 USB PHY PWRRDY
> > > > > signal control (if use USB) SYS_USB_PWRRDY Step 10, Cortex-A55 PCIe
> > > > > RST_RSM_B signal control (if use PCIe) SYS_PCIE_RST_RSM_B
> > > > 
> > > > Note *if use*: how does the TF-A know if USB/PCIe is used by Linux? The documentation mention to set
> > > > it *if use*. Same note is on ALL_ON to VBATT transition documentation (namely "if using USB", "if
> > > > using PCIe"). If TF-A will do this it should set this signals unconditionally. It will not be
> > > > something wrong though. We don't know at the moment what this involves in terms of power consumption,
> > > > if it means something...
> > > 
> > > IIUC,
> > > The only information we have is,
> > > 
> > > "SYS_USB_PWRRDY and SYS_PCIE_RST_RSM_B are used when transition from ALL_ON to AWO (or from AWO to ALL_ON).
> > > "When turning off USB PHY and PCIe PHY, if they are not controlled, PHY may break"
> > > 
> > > ALL_ON to AWO_MODE state transition: 
> > > USB/PCIe are part of PD_ISOVCC power domain and before turning PD_ISOVCC to off,
> > > we need to set USBPWRRDY signal.
> > > 
> > > AWO_MODE to ALL_ON state transition:
> > > 
> > > Turn on PD_ISOVCC first, then clr USBPWRRDY signal for USB usage in linux.
> > > 
> > > Maybe we need to ask hw team, exact usage of USBPWRRDY signal other than state transition.
> > 
> > As you may already know, this is open for quite some time and is ongoing.
> 
> I got more clarification about the USB PWRRDY signal from the HW team.
> 
> The conclusion is that the USB PWRRDY is a signal controlled by SYSC
> controller that goes to the USB PHY and it tells the USB PHY if the power
> supply is ready or not.
> 
> In the diagram at [1] the PWRRDY signal need to be asserted/de-asserted
> before/after G6, G7, G8, G9, G10 signals.
> 
> Philipp,
> 
> Can you please confirm that you don't want this signal to be implemented as
> a reset signal to know clearly your input on it? I would like to start
> looking for another approach in that case.

If this is not a reset signal I don't want it to be implemented as one.

regards
Philipp