[PATCH] usb: host: ehci-generic: check for companion controller

[Marek Vasut]

On 8/30/23 10:00, Fabrice Gasnier wrote:
> EHCI is usually used with companion controller (like OHCI) as companion
> controller. This information on the companion is missing currently in
> companion drivers.
> So, if the usb-uclass isn't aware, it may scan busses in any order: OHCI
> first, then EHCI.
> This is seen on STM32MP1 where DT probing makes the probe order to occur
> by increasing address (OHCI address < EHCI address).
> 
> When a low speed or full-speed device is plugged in, it's not detected as
> EHCI should first detect it, and give ownership (handover) to OHCI.
> 
> Current situation on STM32MP1 (with a low speed device plugged-in)
> STM32MP> usb start
> starting USB...
> Bus usb at 5800c000: USB OHCI 1.0
> Bus usb at 5800d000: USB EHCI 1.00
> scanning bus usb at 5800c000 for devices... 1 USB Device(s) found
> scanning bus usb at 5800d000 for devices... 1 USB Device(s) found
>         scanning usb for storage devices... 0 Storage Device(s) found
> 
> The "companion" property in the device tree allow to retrieve companion
> controller information, from the EHCI node. This allow marking the
> companion driver as such.
> 
> With this patch (same low speed device plugged in):
> STM32MP> usb start
> starting USB...
> Bus usb at 5800c000: USB OHCI 1.0
> Bus usb at 5800d000: USB EHCI 1.00
> scanning bus usb at 5800d000 for devices... 1 USB Device(s) found
> scanning bus usb at 5800c000 for devices... 2 USB Device(s) found
>         scanning usb for storage devices... 0 Storage Device(s) found
> STM32MP> usb tree
> USB device tree:
>    1  Hub (12 Mb/s, 0mA)
>    |   U-Boot Root Hub
>    |
>    +-2  Human Interface (1.5 Mb/s, 100mA)
>         HP HP USB 1000dpi Laser Mouse
> 
>    1  Hub (480 Mb/s, 0mA)
>       u-boot EHCI Host Controller
> 
> This also optimize bus scan when a High speed device is plugged in, as
> the usb-uclass skips OHCI in this case:
> 
> STM32MP> usb reset
> resetting USB...
> Bus usb at 5800c000: USB OHCI 1.0
> Bus usb at 5800d000: USB EHCI 1.00
> scanning bus usb at 5800d000 for devices... 2 USB Device(s) found
>         scanning usb for storage devices... 1 Storage Device(s) found
> STM32MP> usb tree
> USB device tree:
>    1  Hub (480 Mb/s, 0mA)
>    |  u-boot EHCI Host Controller
>    |
>    +-2  Mass Storage (480 Mb/s, 200mA)
>         SanDisk Cruzer Blade 03003432021922011407
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier at foss.st.com>
> ---
> 
>   drivers/usb/host/ehci-generic.c | 24 ++++++++++++++++++++++++

More of a design question -- shouldn't the usb-uclass handle this 
property ad manipulate with private data of "remote" devices instead ?