Hi Finn,
On Thu, Oct 3, 2024 at 5:27 AM Finn Thain <fthain@xxxxxxxxxxxxxx> wrote:
> The m48t59 driver is needed by both SPARC and MVME systems. Linux on
> MVME uses 1970 as "year zero" rather than 1968 that's used on SPARC.
> Add support for the MVME convention. Otherwise, the RTC on non-SPARC
> systems can only read and write dates between 1900 and 1999.
>
> Tested-by: Daniel Palmer <daniel@xxxxxxxx>
> Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxx>
Thanks for your patch!
> --- a/drivers/rtc/rtc-m48t59.c
> +++ b/drivers/rtc/rtc-m48t59.c
> @@ -57,6 +57,17 @@ m48t59_mem_readb(struct device *dev, u32 ofs)
> return readb(m48t59->ioaddr+ofs);
> }
>
> +/*
> + * Sun SPARC machines count years since 1968. MVME machines running Linux
> + * count years since 1970.
> + */
> +
> +#ifdef CONFIG_SPARC
> +#define YEAR0 68
> +#else
+#define YEAR0 70
> +#endif
This causes a change in behavior on other non-SPARC platforms,
if any out-of-tree platform exists that uses this driver.
So I'd rather use:
#elif defined(CONFIG_VME)
#define YEAR0 70
#else
#define YEAR0 0
#endif
> +
> /*
> * NOTE: M48T59 only uses BCD mode
> */
> @@ -82,10 +93,7 @@ static int m48t59_rtc_read_time(struct device *dev, struct rtc_time *tm)
> dev_dbg(dev, "Century bit is enabled\n");
> tm->tm_year += 100; /* one century */
> }
> -#ifdef CONFIG_SPARC
> - /* Sun SPARC machines count years since 1968 */
> - tm->tm_year += 68;
> -#endif
> + tm->tm_year += YEAR0;
Upon closer look, the driver uses platform data, so a better solution
would be to add the year0 offset to struct m48t59_plat_data.
Another suggestion for improvement, not related to this patch,
would be to differentiate among M48T59, M48T02, and M48T08 by using
platform_driver.id_table and platform_device_id.driver_data, instead
of m48t59_plat_data.type.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
