[PATCH v2] common: usb-hub: Reset USB 3.0 hubs only

[Marek Vasut]

On 2/14/24 10:54, Shantur Rathore wrote:
> Additional testing of the changes introduced in commit 33e06dcbe57a "common:
> usb-hub: Reset hub port before scanning") revealed that some USB 2.0 and 3.0
> flash drives didn't work in U-Boot on some Allwinner SoCs that support USB
> 2.0 interfaces only.  More precisely, some of the tested USB 2.0 and 3.0
> flash drives failed to be detected and work on an OrangePi Zero 3, based on
> the Allwinner H616 SoC that supports USB 2.0 only, while the same USB flash
> drives worked just fine on a Pine64 H64, based on the Allwinner H6 SoC that
> supports both USB 2.0 and USB 3.0 interfaces.
> 
> The USB ID of the above-mentioned USB 3.0 flash drive that failed to work is
> 1f75:0917 (Innostor Technology Corporation IS917 Mass storage), it is 32 GB
> in size and sold under the PNY brand.  The mentioned USB 2.0 drive is some
> inexpensive no-name drive with an invalid USB ID.
> 
> Resetting USB 3.0 hubs only, which this patch introduces to the USB hub
> resets, has been tested to work as expected, resolving the identified issues
> on the Allwinner H616, while not introducing any new issues on other tested
> Allwinner SoCs.  Thus, let's fix it that way.
> 
> According to the USB 3.0 specification, resetting a USB 3.0 port is required
> when an attached USB device transitions between different states, such as
> when it resumes from suspend.  Though, the Linux kernel performs additional
> USB 3.0 port resets upon initial USB device attachment, as visible in commit
> 07194ab7be63 ("USB: Reset USB 3.0 devices on (re)discovery") in the kernel
> source, to ensure proper state of the USB 3.0 hub port and proper USB mode
> negotiation during the initial USB device attachment and enumeration.
> 
> These additional types of USB port resets don't exist for USB 2.0 hubs,
> according the USB 2.0 specification.  The resets seem to be added to the USB
> 3.0 specification as part of the port and device mode negotiation.
> 
> The Linux kernel resets USB 3.0 (i.e. SuperSpeed) hubs only, as visible in
> commit 10d674a82e55 ("USB: When hot reset for USB3 fails, try warm reset.")
> in the kernel source.  The check for SuperSpeed hubs is performed in a way
> that also applies to newer SuperSpeed Plus (USB 3.1 or 3.2) hubs as well,
> which hopefully makes it future proof.
> 
> Fixes: commit 33e06dcbe57a ("common: usb-hub: Reset hub port before scanning")
> 
> Link:
> https://lore.kernel.org/u-boot/20240207102327.35125-1-i@shantur.com/T/#u
> Link:
> https://lore.kernel.org/u-boot/20240201164604.13315fa6@donnerap.manchester.arm.com/T/#u
> 
> Signed-off-by: Shantur Rathore <i at shantur.com>
> Helped-by: Dragan Simic <dsimic at manjaro.org>
> Tested-by: Andre Przywara <andre.przywara at arm.com>
> Reviewed-by: Dragan Simic <dsimic at manjaro.org>

Reviewed-by: Marek Vasut <marex at denx.de>