Oh come on, you sent that patch only a week ago and v2 had a so obvious mistake that my trust in your code quality is now very low. On 15/10/2019 16:08:27+0800, Jinke Fan wrote: > When using following operations: > date -s "21190910 19:20:00" > hwclock -w > to change date from 2019 to 2119 for test, it will fail on Hygon > Dhyana and AMD Zen CPUs, while the same operations run ok on Intel i7 > platform. > > MC146818 driver use function mc146818_set_time() to set register > RTC_FREQ_SELECT(RTC_REG_A)'s bit4-bit6 field which means divider stage > reset value on Intel platform to 0x7. > > While AMD/Hygon RTC_REG_A(0Ah)'s bit4 is defined as DV0 [Reference]: > DV0 = 0 selects Bank 0, DV0 = 1 selects Bank 1. Bit5-bit6 is defined > as reserved. > > DV0 is set to 1, it will select Bank 1, which will disable AltCentury > register(0x32) access. As UEFI pass acpi_gbl_FADT.century 0x32 > (AltCentury), the CMOS write will be failed on code: > CMOS_WRITE(century, acpi_gbl_FADT.century). > > Correct RTC_REG_A bank select bit(DV0) to 0 on AMD/Hygon CPUs, it will > enable AltCentury(0x32) register writing and finally setup century as > expected. > > Test results on AMD/Hygon machine show that it works as expected. > > Reference: > https://www.amd.com/system/files/TechDocs/51192_Bolton_FCH_RRG.pdf > section: 3.13 Real Time Clock (RTC) > > Reported-by: kbuild test robot <lkp@xxxxxxxxx> > Signed-off-by: Jinke Fan <fanjinke@xxxxxxxx> > --- > > v2->v3: > - Make the changes only relevant to AMD/Hygon. > > v1->v2: > - Fix the compile errors on sparc64/alpha platform. > > drivers/rtc/rtc-mc146818-lib.c | 11 ++++++++++- > include/linux/mc146818rtc.h | 6 ++++++ > 2 files changed, 16 insertions(+), 1 deletion(-) > > diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c > index 2ecd8752b088..70502881785d 100644 > --- a/drivers/rtc/rtc-mc146818-lib.c > +++ b/drivers/rtc/rtc-mc146818-lib.c > @@ -172,7 +172,16 @@ int mc146818_set_time(struct rtc_time *time) > save_control = CMOS_READ(RTC_CONTROL); > CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); > save_freq_select = CMOS_READ(RTC_FREQ_SELECT); > - CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); > + > +#ifdef CONFIG_X86 > + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || > + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) > + CMOS_WRITE((save_freq_select & (~RTC_DV0)), RTC_FREQ_SELECT); > + else > + CMOS_WRITE((save_freq_select | RTC_DIV_RESET2), RTC_FREQ_SELECT); > +#else > + CMOS_WRITE((save_freq_select | RTC_DIV_RESET2), RTC_FREQ_SELECT); > +#endif > > #ifdef CONFIG_MACH_DECSTATION > CMOS_WRITE(real_yrs, RTC_DEC_YEAR); > diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h > index 0661af17a758..7066a7bced61 100644 > --- a/include/linux/mc146818rtc.h > +++ b/include/linux/mc146818rtc.h > @@ -86,6 +86,12 @@ struct cmos_rtc_board_info { > /* 2 values for divider stage reset, others for "testing purposes only" */ > # define RTC_DIV_RESET1 0x60 > # define RTC_DIV_RESET2 0x70 > + > +#ifdef CONFIG_X86 > + /* DV0 = 0 selects Bank 0, DV0 = 1 selects Bank 1 on AMD/Hygon platform */ > +# define RTC_DV0 0x10 > +#endif > + > /* Periodic intr. / Square wave rate select. 0=none, 1=32.8kHz,... 15=2Hz */ > # define RTC_RATE_SELECT 0x0F > > -- > 2.17.1 > -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
