On 12/22/21 19:20, Mark Kettenis wrote:
From: Thomas Watson <twatso...@icloud.com>
Date: Tue, 21 Dec 2021 19:36:16 -0600
Using the XHCI driver, the function `usb_kbd_poll_for_event` takes
30-40ms to run. The exact time is dependent on the polling interval the
keyboard requests in its descriptor, and likely cannot be significantly
reduced without major rework to the XHCI driver.
The U-Boot EFI console service sets a timer to poll the keyboard every 5
microseconds, and this timer is checked every time a block is read off
disk. The net effect is that, on my system, loading a ~40MiB kernel and
initrd takes about 62 seconds with a slower keyboard and 53 seconds
with a faster one, with the vast majority of the time spent polling the
keyboard.
To solve this problem, this patch adds a 20ms delay between consecutive
calls to `usb_kbd_poll_for_event`. This is sufficient to reduce the
total loading time to under half a second for both keyboards, and does
not impact the perceived keystroke latency.
Signed-off-by: Thomas Watson <twatso...@icloud.com>
---
I can confirm that plugging in a usb keyboard makes loading a kernel
annoyingly slow when booting through EFI. And this looks like a
reasonable approach to fix this to me. Minor nit: I think you should
reflow the comment you're adding such that it fits within the standard
80 character line limit.
That, and please make sure the patch applies on u-boot/master (currently
it does not). Use git send-email if your mailer reformats the patches.
