[PATCH v2 07/10] rtc: sandbox-rtc: fix set method

[Simon Glass]

On Tue, 19 May 2020 at 16:01, Rasmus Villemoes
<rasmus.villemoes at prevas.dk> wrote:
>
> The current set method is broken; a simple test case is to first set
> the date to something in April, then change the date to 31st May:
>
> => date 040412122020.34
> Date: 2020-04-04 (Saturday)    Time: 12:12:34
> => date 053112122020.34
> Date: 2020-05-01 (Friday)    Time: 12:12:34
>
> or via the amending of the existing rtc_set_get test case similarly:
>
> $ ./u-boot -T -v
> => ut dm rtc_set_get
> Test: dm_test_rtc_set_get: rtc.c
> expected: 31/08/2004 18:18:00
> actual: 01/08/2004 18:18:00
>
> The problem is that after each register write,
> sandbox_i2c_rtc_complete_write() gets called and sets the internal
> time from the current set of registers. However, when we get to
> writing 31 to mday, the registers are in an inconsistent state (mon is
> still 4), so the mktime machinery ends up translating April 31st to
> May 1st. Upon the next register write, the registers are populated by
> sandbox_i2c_rtc_prepare_read(), so the 31 we just wrote to mday gets
> overwritten by a 1.
>
> Fix it by writing all registers at once, and for consistency, update
> the get method to retrieve them all with one "i2c transfer".
>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
> ---
>  drivers/rtc/sandbox_rtc.c | 65 +++++++++++++++------------------------
>  test/dm/rtc.c             | 15 ++++++++-
>  2 files changed, 38 insertions(+), 42 deletions(-)

Nice fix!

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