Dear Greg,


Am 05.05.21 um 10:33 schrieb Greg Kroah-Hartman:
> On Wed, May 05, 2021 at 10:27:52AM +0200, Paul Menzel wrote:

>> Am 05.05.21 um 10:11 schrieb Greg Kroah-Hartman:
>>> On Wed, May 05, 2021 at 09:57:44AM +0200, Paul Menzel wrote:
>>
>>>> On an Asus F2A85-M PRO, BIOS 6601 11/25/2014, with an ASM1042 SuperSpeed USB
>>>> Host Controller [1b21:1042], and the xHCI drivers built as modules
>>>>
>>>>       CONFIG_USB_XHCI_PCI=m
>>>>       CONFIG_USB_XHCI_HCD=m
>>>>
>>>> `quirk_usb_handoff_xhci` takes 60 ms, which is 15 % of the time to reaching
>>>> `run_init_process()`. I addded some prints, showing the f
>>>>
>>>>       [    0.308841] pci 0000:03:00.0: PCI->APIC IRQ transform: INT A -> IRQ 17
>>>>       [    0.369858] pci 0000:03:00.0: handshake done with timeout = 0
>>>>       [    0.369862] pci 0000:03:00.0: hc_init reached
>>>>       [    0.369865] pci 0000:03:00.0: second handshake done
>>>>       [    0.369869] pci 0000:03:00.0: third handshake done
>>>>       [    0.369909] pci 0000:03:00.0: quirk_usb_early_handoff+0x0/0x670 took 59661 usecs
>>>>       […]
>>>>       [    0.415223] Run /lib/systemd/systemd as init process
>>>>
>>>> Is there a way to optimize this, or move it out “the hot path”?
>>>
>>> That's the hardware taking so long, all that function does is make some
>>> PCI calls to the device.
>>
>> In your experience, do most devices take that long?
> 
> No idea, it all depends on the device.  And is 60ms really that long to
> initialize the USB controller?

For the goal of “instant” startup, I’d say yes.

I also guess, this is all the ASMedia ASM1042 firmware taking so long, 
right?

> That's a complex beast.

I miss the PS/2 controller, which seemed to be simpler for *input* 
devices like keyboard and mouse. (No idea regarding power usage even.)

>>> If the driver is built as a module, there should not be any "hot
>>> path" here as the module is loaded async when the device is
>>> discovered, right?
>>      obj-$(CONFIG_USB_PCI)   += pci-quirks.o
>>
>> So all quirks are run independently of the USB “variant” (UHCI, OHCI, EHCI,
>> xHCI).
>>
>> Indeed, this driver is built into the Linux kernel.
>>
>>      $ grep USB_PCI .config
>>      CONFIG_USB_PCI=y
>>
>> So, should `pci-quirks.c` be split up to have more fine grained control?
> 
> What control do you need here?

Good question, as I do not know the USB spec. I’d say, disabling certain 
quirks, or just run them, when the actual driver is loaded.

> And yeah, I see, but this code has to be run at early-startup to match
> the USB spec requirements for handing off the USB control from the
> BIOS/firmware/whatever, to the kernel.

That makes the second option above a moot point.

> Try changing your BIOS settings to not have "legacy" USB support in it,
> that could cause this transition to go faster, at the expense of not
> being able to use a USB device before Linux boots.

The firmware of the Asus F2A85-M PRO allows to disable *legacy* USB 
support for only the ASMedia ASM1042. And, thank you for the suggestion, 
it helped. `quirk_usb_early_handoff()` does not show up in the logs now, 
meaning it’s below 50 ms. And it is well below: less than one millisecond.

     [    0.308343] pci 0000:00:15.1: PCI->APIC IRQ transform: INT A -> 
IRQ 16
     [    0.308359] pci 0000:03:00.0: PCI->APIC IRQ transform: INT A -> 
IRQ 17
     [    0.308376] pci 0000:03:00.0: hc_init reached
     [    0.308380] pci 0000:03:00.0: second handshake done
     [    0.308384] pci 0000:03:00.0: third handshake done
     [    0.308395] PCI: CLS 64 bytes, default 64
     […]
     [    0.401722] Run /lib/systemd/systemd as init process

> And is this really the slowest thing at startup for you that it is the
> last thing that needs to be optimized?

At least with decreasing SMP boot init time of the table, it was the 
biggest issue. 400 ms to init on an (old) x86 desktop board seems quite 
good. If you see something else in the attached log messages, I am all ears.

(By the way, as the harddisk is not encrypted, I am booting without initrd.)


Kind regards,

Paul