Hello,
On 16/08/2021 21:47:18+0800, Tony W Wang-oc wrote:
> When the RTC divider is changed from reset to an operating time base,
> the first update cycle should be 500ms later. But on some Zhaoxin SOCs,
> this first update cycle is one second later.
>
> So set RTC time on these Zhaoxin SOCs will causing 500ms delay.
>
Can you explain what is the relationship between writing the divider and
the 500ms delay?
Isn't the issue that you are using systohc and set_offset_nsec is set to
NSEC_PER_SEC / 2 ?
> Skip setup RTC divider on these SOCs in mc146818_set_time to fix it.
>
> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx>
> ---
> drivers/rtc/rtc-mc146818-lib.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
> index dcfaf09..322f94b 100644
> --- a/drivers/rtc/rtc-mc146818-lib.c
> +++ b/drivers/rtc/rtc-mc146818-lib.c
> @@ -190,8 +190,18 @@ int mc146818_set_time(struct rtc_time *time)
> spin_lock_irqsave(&rtc_lock, flags);
> save_control = CMOS_READ(RTC_CONTROL);
> CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
> +
> +#ifdef CONFIG_X86
> + if (!((boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR ||
> + boot_cpu_data.x86_vendor == X86_VENDOR_ZHAOXIN) &&
> + (boot_cpu_data.x86 <= 7 && boot_cpu_data.x86_model <= 59))) {
> + save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
> + CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
> + }
> +#else
> save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
> CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
> +#endif
>
> #ifdef CONFIG_MACH_DECSTATION
> CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
> @@ -209,7 +219,15 @@ int mc146818_set_time(struct rtc_time *time)
> #endif
>
> CMOS_WRITE(save_control, RTC_CONTROL);
> +
> +#ifdef CONFIG_X86
> + if (!((boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR ||
> + boot_cpu_data.x86_vendor == X86_VENDOR_ZHAOXIN) &&
> + (boot_cpu_data.x86 <= 7 && boot_cpu_data.x86_model <= 59)))
> + CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
> +#else
> CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
> +#endif
>
> spin_unlock_irqrestore(&rtc_lock, flags);
>
> --
> 2.7.4
>
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
