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

[Dragan Simic]

On 2024-02-19 19:24, Marek Vasut wrote:
> 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")

Oh, I just noticed that "commit" somehow ended up here by mistake.
Please remove it before applying.

>> 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>