On 12/22/21 19:20, Mark Kettenis wrote:
From: Thomas Watson twatson52@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 twatson52@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.