Re: [PATCH v8 4/7] reset: rzg2l-usbphy-ctrl: Add support for USB PWRRDY

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

On Do, 2025-10-23 at 16:58 +0300, Claudiu wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> 
> On the Renesas RZ/G3S SoC, the USB PHY block has an input signal called
> PWRRDY. This signal is managed by the system controller and must be
> de-asserted after powering on the area where USB PHY resides and asserted
> before powering it off.
> 
> On power-on/resume the USB PWRRDY signal need to be de-asserted before
> enabling clock and switching the module to normal state (through MSTOP
> support). The power-on/resume configuration sequence must be:
> 
> 1/ PWRRDY=0
> 2/ CLK_ON=1
> 3/ MSTOP=0
> 
> On power-off/suspend the configuration sequence should be:
> 
> 1/ MSTOP=1
> 2/ CLK_ON=0
> 3/ PWRRDY=1
> 
> The CLK_ON and MSTOP functionalities are controlled by clock drivers.
> The suspend/resume support will be handled by different patches.
> 
> After long discussions with the internal HW team, it has been confirmed
> that the HW connection b/w USB PHY block, the USB channels, the system
> controller, clock, MSTOP, PWRRDY signal is as follows:
> 
>                                ┌──────────────────────────────┐
>                                │                              │◄── CPG_CLKON_USB.CLK0_ON
>                                │     USB CH0                  │
> ┌──────────────────────────┐   │┌───────────────────────────┐ │◄── CPG_CLKON_USB.CLK2_ON
> │                 ┌────────┐   ││host controller registers  │ │
> │                 │        │   ││function controller registers│
> │                 │ PHY0   │◄──┤└───────────────────────────┘ │
> │     USB PHY     │        │   └────────────▲─────────────────┘
> │                 └────────┘                │
> │                          │    CPG_BUS_PERI_COM_MSTOP.MSTOP{6, 5}_ON
> │┌──────────────┐ ┌────────┐
> ││USHPHY control│ │        │
> ││  registers   │ │ PHY1   │   ┌──────────────────────────────┐
> │└──────────────┘ │        │◄──┤     USB CH1                  │
> │                 └────────┘   │┌───────────────────────────┐ │◄── CPG_CLKON_USB.CLK1_ON
> └─▲───────▲─────────▲──────┘   ││ host controller registers │ │
>   │       │         │          │└───────────────────────────┘ │
>   │       │         │          └────────────▲─────────────────┘
>   │       │         │                       │
>   │       │         │           CPG_BUS_PERI_COM_MSTOP.MSTOP7_ON
>   │PWRRDY │         │
>   │       │   CPG_CLK_ON_USB.CLK3_ON
>   │       │
>   │  CPG_BUS_PERI_COM_MSTOP.MSTOP4_ON
>   │
> ┌────┐
> │SYSC│
> └────┘
> 
> where:
> - CPG_CLKON_USB.CLK.CLKX_ON is the register bit controlling the clock X
>   of different USB blocks, X in {0, 1, 2, 3}
> - CPG_BUS_PERI_COM_MSTOP.MSTOPX_ON is the register bit controlling the
>   MSTOP of different USB blocks, X in {4, 5, 6, 7}
> - USB PHY is the USB PHY block exposing 2 ports, port0 and port1, used
>   by the USB CH0, USB CH1
> - SYSC is the system controller block controlling the PWRRDY signal
> - USB CHx are individual USB block with host and function capabilities
>   (USB CH0 have both host and function capabilities, USB CH1 has only
>   host capabilities)
> 
> The USBPHY control registers are controlled though the
> reset-rzg2l-usbphy-ctrl driver. The USB PHY ports are controlled by
> phy_rcar_gen3_usb2 (drivers/phy/renesas/phy-rcar-gen3-usb2.c file). The
> USB PHY ports request resets from the reset-rzg2l-usbphy-ctrl driver.
> 
> The connection b/w the system controller and the USB PHY CTRL driver is
> implemented through the renesas,sysc-pwrrdy device tree property
> proposed in this patch. This property specifies the register offset and the
> bitmask required to control the PWRRDY signal.
> 
> Since the USB PHY CTRL driver needs to be probed before any other
> USB-specific driver on RZ/G3S, control of PWRRDY is passed exclusively
> to it. This guarantees the correct configuration sequence between clocks,
> MSTOP bits, and the PWRRDY bit on probe/resume and remove/suspend. At the
> same time, changes are kept minimal by avoiding modifications to the USB
> PHY driver to also handle the PWRRDY itself.
> 
> Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>

regards
Philipp