[PATCH v2] time: Fix get_ticks being non-monotonic

[Simon Glass]

On Wed, 9 Sep 2020 at 14:25, Sean Anderson <seanga2 at gmail.com> wrote:
>
> get_ticks does not always succeed. Sometimes it can be called before the
> timer has been initialized. If it does, it returns a negative errno.
> This causes the timer to appear non-monotonic, because the value will
> become much smaller after the timer is initialized.
>
> No users of get_ticks which I checked handle errors of this kind. Further,
> functions like tick_to_time mangle the result of get_ticks, making it very
> unlikely that one could check for an error without suggesting a patch such
> as this one.
>
> This patch panics if we ever get an error. There are two cases in which
> this can occur. The first is if we couldn't find/probe the timer for some
> reason. One reason for this is if the timer is not available so early. This
> likely indicates misconfiguration. Another reason is that the timer has an
> invalid/missing device tree binding. In this case, panicing is also
> correct. The second case covers errors calling get_count. This can only
> occur if the timer is missing a get_count function (or on RISC-V, but that
> should be fixed soon).
>
> Fixes: c8a7ba9e6a5
> Signed-off-by: Sean Anderson <seanga2 at gmail.com>
> ---
>
> Changes in v2:
> - Panic on error
>
>  lib/time.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Simon Glass <sjg at chromium.org>