[PATCH v4 08/14] lib: time: hook uthread_schedule() into udelay()

[Ilias Apalodimas]

On Tue, 18 Mar 2025 at 12:47, Jerome Forissier
<jerome.forissier at linaro.org> wrote:
>
> Introduce a uthread scheduling loop into udelay() when CONFIG_UTHREAD
> is enabled. This means that any uthread calling into udelay() may yield
> to uthread and be scheduled again later. There is no delay in the
> scheduling loop because tests have shown that such a delay can have a
> detrimental effect on the console (input drops characters).
>
> Signed-off-by: Jerome Forissier <jerome.forissier at linaro.org>
> ---
>  lib/time.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/lib/time.c b/lib/time.c
> index d88edafb196..0e9b079f9cf 100644
> --- a/lib/time.c
> +++ b/lib/time.c
> @@ -17,6 +17,7 @@
>  #include <asm/global_data.h>
>  #include <asm/io.h>
>  #include <linux/delay.h>
> +#include <uthread.h>
>
>  #ifndef CFG_WD_PERIOD
>  # define CFG_WD_PERIOD (10 * 1000 * 1000)      /* 10 seconds default */
> @@ -197,7 +198,13 @@ void udelay(unsigned long usec)
>         do {
>                 schedule();
>                 kv = usec > CFG_WD_PERIOD ? CFG_WD_PERIOD : usec;
> -               __udelay(kv);
> +               if (CONFIG_IS_ENABLED(UTHREAD)) {
> +                       ulong t0 = timer_get_us();
> +                       while (timer_get_us() - t0 < kv)
> +                               uthread_schedule();
> +               } else {
> +                       __udelay(kv);
> +               }
>                 usec -= kv;
>         } while(usec);
>  }
> --
> 2.43.0
>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>