[PATCH v4 0/2] arm: dts: rockchip: rk3399: usb: ehci: Fix EHCI probe in rk3399 to access peripherals by USB 2.

[Marek Vasut]

On 12/9/22 16:39, Xavier Drudis Ferran wrote:
> 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.
> 
> This series is a second attempt to implement option 5 as Marek Vasut
> requested in December 5th.  Options 1 and 3 didn't get through[2,3].
> 
> The first patch in the series (identical to v3) just registers usb2phy
> as a clock driver (device_bind_driver() didn't work but
> device_bind_driver_to_node() did), without any specific operations, so
> that ehci-generic.c finds it and is happy. It worked in my tests on a
> Rock Pi 4 B+ (rk3399).
> 
> Since Marek Vasut objected to an operationless driver[4], the second
> patch adds enable and disable operations adapted from linux prepare
> and unprepare operations (and round_rate(), which doesn't seem very
> useful anyway since it's a fixed clock). Since there're no users of
> this clock in u-boot, I can't see any difference in my tests with only
> the first patch or both, so I can't be sure it really works if it's
> ever needed, but it's hopefully more complete.
> 
> Links: [1] https://lkml.kernel.org/lkml/1731551.Q6cHK6n5ZM@phil/T/
>         [2] https://patchwork.ozlabs.org/project/uboot/patch/20220701185959.GC1700@begut/#2954536
>         [3] https://patchwork.ozlabs.org/project/uboot/patch/Y44+ayJfUlI08ptM@localhost/#3016099
>         [4] https://patchwork.ozlabs.org/project/uboot/patch/Y5IWpjYLB4aXMy9o@localhost/#3018135

+CC Philipp, Quentin