[U-Boot] [PATCH v3 1/2] console: usbkbd: Improve TFTP booting performance
Stephen Warren
swarren at wwwdotorg.org
Thu Jun 27 20:20:04 CEST 2013
On 06/27/2013 03:45 AM, Jim Lin wrote:
> TFTP booting is observed a little bit slow, especially when a USB
> keyboard is installed.
> The fix is to move polling to every second if we sense that other task
> like TFTP boot is running.
>
> diff --git a/common/usb_kbd.c b/common/usb_kbd.c
> +#ifdef CONFIG_USBKB_TESTC_PERIOD
> + /*
> + * T is the time between two calls of usb_kbd_testc().
> + * If CONFIG_USBKB_TESTC_PERIOD ms < T < 1000 ms,
> + * it implies other task like TFTP boot is running,
> + * then we reduce polling to every second
> + * to improve TFTP booting performance.
> + */
> + if ((get_timer(kbd_testc_tms) >=
> + (CONFIG_USBKB_TESTC_PERIOD * CONFIG_SYS_HZ / 1000)) &&
> + (get_timer(kbd_testc_tms) < CONFIG_SYS_HZ))
> + return 0;
> + else
> + kbd_testc_tms = get_timer(0);
> +#endif
I have a hard time understanding why the fact that "some other task is
running" implies anything at all re: how often usb_kbd_testc() would be
called.
It's quite possible that "some other task" is extremely fine-grained,
and calls usb_kbd_testc() every 0.1ms, and would be severely negatively
affected by usb_kbd_testc() taking a long time to execute.
Conversly, it's quite possible that "some other task" is quite granular,
and calls usb_kbd_testc() a wide intervals, say every 200ms.
So, I think this change keys of entirely the wrong thing.
Shouldn't the TFTP process (or use of USB networking?) or other
long-running tasks that do check for keyboard IO simply set some flag to
indicate to usb_kbd_testc() that it should run at a reduced rate, or
even just have those long-running processses call usb_kbd_testc() at a
reduced rate themselves?
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