[PATCH] arm: dts: rockchip: rk3399: usb: ehci: Fix EHCI probe in rk3399 to access peripherals by USB 2.

[Xavier Drudis Ferran]

I just checked this still works in next. No v2 needed (until feedback,
because I've heard about nodes providing two devices and maybe you
prefer that, so far I'd still see it too complex).

El Fri, Jul 01, 2022 at 08:59:59PM +0200, Xavier Drudis Ferran deia:
> 
> arch/arm/dts/rk3399.dtsi has a node
> 
>   usb_host0_ehci: usb at fe380000 {
>        compatible = "generic-ehci";
> 
> with clocks:
> 
>        clocks = <&cru HCLK_HOST0>, <&cru HCLK_HOST0_ARB>,
>                 <&u2phy0>;
> 
> The first 2 refer to nodes with class UCLASS_CLK, but &u2phy0
> has class UCLASS_PHY.
> 
>   u2phy0: usb2phy at e450 {
>        compatible = "rockchip,rk3399-usb2phy";
> 
> Since clk_get_bulk() only looks for devices with UCLASS_CLK,
> it fails with -ENODEV and then ehci_usb_probe() aborts.
> 
> The consequence is peripherals connected to a USB 2 port (e.g. in a
> Rock Pi 4 the white port, nearer the edge) not being detected.
> They're detected if CONFIG_USB_OHCI_GENERIC is selected in Kconfig,
> because ohci_usb_probe() does not abort when one clk_get_by_index()
> fails, but then they work in USB 1 mode,.
> 
> rk3399.dtsi comes from linux and the  u2phy0 was added[1] to the clock
> list in:
> 
>     commit b5d1c57299734f5b54035ef2e61706b83041f20c
>     Author: William wu <wulf at rock-chips.com>
>     Date:   Wed Dec 21 18:41:05 2016 +0800
> 
>     arm64: dts: rockchip: add u2phy clock for ehci and ohci of rk3399
> 
>     We found that the suspend process was blocked when it run into
>     ehci/ohci module due to clk-480m of usb2-phy was disabled.
>     [...]
> 
> Suspend concerns don't apply to U-Boot, and the problem with U-Boot
> failing to probe EHCI doesn't apply to linux, because in linux
> rockchip_usb2phy_clk480m_register makes u2phy0 a proper clock provider
> when called by rockchip_usb2phy_probe().
> 
> So I can think of a few alternative solutions:
> 
> 1- Change ehci_usb_probe() to make it more similar to
>    ohci_usb_probe(), and survive failure to get one clock. Looks a
>    little harder, and I don't know whether it could break something if
>    it ignored a clock that was important for something else than
>    suspend.
> 
> 2- Change rk3399.dtsi effecttively reverting the linux commit
>    b5d1c57299734f5b54035ef2e61706b83041f20c. This dealigns the .dtsi
>    from linux and seems fragile at the next synchronisation.
> 
> 3- Change the clock list in rk3399-u-boot.dtsi or somewhere else.
>    This survives .dts* sync but may survive "too much" and miss some
>    change from linux that we might want.
> 
> 4- Enable CONFIG_USB_OHCI_GENERIC and use the ports in USB 1 mode.
>    This would need to be made for all boards using rk3399.  In a
>    simple test reading one file from USB storage it gave 769.5 KiB/s
>    instead of 20.5 MiB/s with solution 2.
> 
> 5- Trying to replicate linux and have usb2phy somehow provide a clk,
>    or have a separate clock device for usb2phy in addition to the phy
>    device. I just can't seem to imagine how to achieve this with the
>    U-Boot driver model, maybe because of my limited familiarity with
>    it.
> 
> This patch is option 3. Looked like the simplest and most performant.
> But it might not be what's wanted, so comments wellcome.
> 
> Link: [1] https://lkml.kernel.org/lkml/1731551.Q6cHK6n5ZM@phil/T/
> 
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Philipp Tomsich <philipp.tomsich at vrull.eu>
> Cc: Kever Yang <kever.yang at rock-chips.com>
> Cc: Lukasz Majewski <lukma at denx.de>
> Cc: Sean Anderson <seanga2 at gmail.com>
> Cc: Marek Vasut <marex at denx.de>
> 
> Signed-off-by: Xavier Drudis Ferran <xdrudis at tinet.cat>
> ---
>  arch/arm/dts/rk3399-u-boot.dtsi | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm/dts/rk3399-u-boot.dtsi b/arch/arm/dts/rk3399-u-boot.dtsi
> index 716b9a433a..63c7b10405 100644
> --- a/arch/arm/dts/rk3399-u-boot.dtsi
> +++ b/arch/arm/dts/rk3399-u-boot.dtsi
> @@ -147,3 +147,11 @@
>  &vopl {
>  	u-boot,dm-pre-reloc;
>  };
> +
> +&usb_host0_ehci {
> +	clocks = <&cru HCLK_HOST0>, <&cru HCLK_HOST0_ARB>;
> +};
> +
> +&usb_host1_ehci {
> +	clocks = <&cru HCLK_HOST1>, <&cru HCLK_HOST1_ARB>;
> +};
> -- 
> 2.20.1
>