Re: [PATCH] rtc: s3c-rtc: Avoid using broken ALMYEAR register

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

On 13/11/2018 12:32:50+0100, Marek Szyprowski wrote:
> (RTC,ALM)YEAR registers of Exynos built-in RTC device contains 3 BCD
> characters. s3c-rtc driver uses only 2 lower of them and supports years
> from 2000..2099 range. The third BCD value is typically set to 0, but it
> looks that handling of it is broken in the hardware. It sometimes
> defaults to a random (even non-BCD) value. This is not an issue
> for handling RTCYEAR register, because bcd2bin() properly handles only
> 8bit values (2 BCD characters, the third one is skipped). The problem
> is however with ALMYEAR register and proper RTC alarm operation. When
> YEAREN bit is set for the configured alarm, RTC hardware triggers alarm
> only when ALMYEAR and RTCYEAR matches. This usually doesn't happen
> because of the random noise on the third BCD character.
> 
> Fix this by simply skipping setting ALMYEAR register in alarm
> configuration. This workaround fixes broken alarm operation on Exynos
> built-in rtc device. My tests revealed that the issue happens on the
> following Exynos series: 3250, 4210, 4412, 5250 and 5410.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/rtc/rtc-s3c.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
Applied, thanks.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com