[PATCH v2 12/14] dm: usb: initialize and scan multiple buses simultaneously with uthread

[Jerome Forissier]

On 2/27/25 17:25, Simon Glass wrote:
> Hi Jerome,
> 
> On Tue, 25 Feb 2025 at 09:35, Jerome Forissier
> <jerome.forissier at linaro.org> wrote:
>>
>> Use the uthread framework to initialize and scan USB buses in parallel
>> for better performance. The console output is slightly modified with a
>> final per-bus report of the number of devices found, common to UTHREAD
>> and !UTHREAD. The USB tests are updated accordingly.
>>
>> Tested on two platforms:
>>
>> 1. arm64 QEMU on a somewhat contrived example (4 USB buses, each with
>> one audio device, one keyboard, one mouse and one tablet)
>>
>>  $ make qemu_arm64_defconfig
>>  $ make -j$(nproc) CROSS_COMPILE="ccache aarch64-linux-gnu-"
>>  $ qemu-system-aarch64 -M virt -nographic -cpu max -bios u-boot.bin \
>>      $(for i in {1..4}; do echo -device qemu-xhci,id=xhci$i \
>>          -device\ usb-{audio,kbd,mouse,tablet},bus=xhci$i.0; \
>>      done)
>>
>> 2. i.MX93 EVK (imx93_11x11_evk_defconfig) with two USB hubs, each with
>> one webcam and one ethernet adapter, resulting in the following device
>> tree:
>>
>>  USB device tree:
>>    1  Hub (480 Mb/s, 0mA)
>>    |  u-boot EHCI Host Controller
>>    |
>>    +-2  Hub (480 Mb/s, 100mA)
>>      |  GenesysLogic USB2.1 Hub
>>      |
>>      +-3  Vendor specific (480 Mb/s, 350mA)
>>      |    Realtek USB 10/100/1000 LAN 001000001
>>      |
>>      +-4   (480 Mb/s, 500mA)
>>            HD Pro Webcam C920 8F7CD51F
>>
>>    1  Hub (480 Mb/s, 0mA)
>>    |  u-boot EHCI Host Controller
>>    |
>>    +-2  Hub (480 Mb/s, 100mA)
>>      |   USB 2.0 Hub
>>      |
>>      +-3  Vendor specific (480 Mb/s, 200mA)
>>      |    Realtek USB 10/100/1000 LAN 000001
>>      |
>>      +-4   (480 Mb/s, 500mA)
>>           Generic OnLan-CS30 201801010008
>>
>> Note that i.MX was tested on top of the downstream repository [1] since
>> USB doesn't work in the upstream master branch.
>>
>> [1] https://github.com/nxp-imx/uboot-imx/tree/lf-6.6.52-2.2.0
>>     commit 6c4545203d12 ("LF-13928 update key for capsule")
>>
>> The time spent in usb_init() ("usb start" command) is reported on
>> the console. Here are the results:
>>
>>         | CONFIG_UTHREAD=n | CONFIG_UTHREAD=y
>> --------+------------------+-----------------
>> QEMU    |          5628 ms |          2212 ms
>> i.MX93  |          4591 ms |          2441 ms
>>
>> Signed-off-by: Jerome Forissier <jerome.forissier at linaro.org>
>> ---
>>  drivers/usb/host/usb-uclass.c | 92 ++++++++++++++++++++++++++++-------
>>  test/boot/bootdev.c           | 14 +++---
>>  test/boot/bootflow.c          |  2 +-
>>  3 files changed, 83 insertions(+), 25 deletions(-)
> 
> What happens to output produced by a thread? Does it get stored
> somewhere and written when the thread completes, or do the threads
> intermingle their output?

The latter. That is why I slightly reworked the USB initialization
output to print a status once the threads are done, and I also updated
the related tests as you can see in the patch. For instance the tests
were expecting:
"Bus usb at 1: scanning bus usb at 1 for devices... 5 USB Device(s) found"
The "scanning bus usb at 1 for devices..." part is printed by the threads,
therefore in any order. I decided to move the text
"Bus usb at 1: 5 USB Device(s) found" to after the threads are complete,
iterating over the devices in a deterministic order.

> 
> I'm not sure if you saw my email about using a state machine for USB.
> If so, could you please point me to your reply?

I did, but I did not reply because I did not try. I have a feeling that
the change would be more intrusive than what I did, but above all I am
not doing the uthread thing to address only USB but as a general
technique to make things parallel without too much trouble (at least
that's my hope). So kind of a different goal.

Regards,
-- 
Jerome