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.

common/usb_kbd.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/common/usb_kbd.c b/common/usb_kbd.c index afad260d3d..0131b7dfab 100644 --- a/common/usb_kbd.c +++ b/common/usb_kbd.c @@ -118,7 +118,7 @@ struct usb_kbd_pdata { extern int __maybe_unused net_busy_flag;

/* The period of time between two calls of usb_kbd_testc(). */ -static unsigned long __maybe_unused kbd_testc_tms; +static unsigned long kbd_testc_tms;

/* Puts character in the queue and sets up the in and out pointer. */ static void usb_kbd_put_queue(struct usb_kbd_pdata *data, u8 c) @@ -394,21 +394,31 @@ static int usb_kbd_testc(struct stdio_dev *sdev) struct usb_device *usb_kbd_dev; struct usb_kbd_pdata *data;

• /*

• * Polling the keyboard for an event can take dozens of milliseconds. Add a
  

• * delay between polls to avoid blocking activity which polls rapidly, like
  

• * the UEFI console timer.
  

• */
  

• unsigned long poll_delay = CONFIG_SYS_HZ / 50;

#ifdef CONFIG_CMD_NET /* * If net_busy_flag is 1, NET transfer is running, * then we check key-pressed every second (first check may be * less than 1 second) to improve TFTP booting performance. */

• if (net_busy_flag && (get_timer(kbd_testc_tms) < CONFIG_SYS_HZ))

• return 0;
  

• kbd_testc_tms = get_timer(0);

• if (net_busy_flag)

• poll_delay = CONFIG_SYS_HZ;
  

#endif

• dev = stdio_get_by_name(sdev->name); usb_kbd_dev = (struct usb_device *)dev->priv; data = usb_kbd_dev->privptr;

• usb_kbd_poll_for_event(usb_kbd_dev);

• if (get_timer(kbd_testc_tms) >= poll_delay) {

• usb_kbd_poll_for_event(usb_kbd_dev);
  

• kbd_testc_tms = get_timer(0);
  

• }

  return !(data->usb_in_pointer == data->usb_out_pointer);

}

2.17.1