Message ID | 20220418184933.13172-1-paul@crapouillou.net |
---|---|
Headers | show |
Series | rtc: ingenic: various updates | expand |
On 18/04/2022 19:49:31+0100, Paul Cercueil wrote: > On power loss, reading the RTC value would fail as the scratchpad lost > its magic value, until the hardware clock was set once again. > > To avoid that, reset the RTC value to Epoch in the probe if we detect > that the scratchpad lost its magic value. > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > --- > drivers/rtc/rtc-jz4740.c | 24 +++++++++++++++++++++--- > 1 file changed, 21 insertions(+), 3 deletions(-) > > diff --git a/drivers/rtc/rtc-jz4740.c b/drivers/rtc/rtc-jz4740.c > index 119baf168b32..aac5f68bf626 100644 > --- a/drivers/rtc/rtc-jz4740.c > +++ b/drivers/rtc/rtc-jz4740.c > @@ -42,6 +42,9 @@ > /* Magic value to enable writes on jz4780 */ > #define JZ_RTC_WENR_MAGIC 0xA55A > > +/* Value written to the scratchpad to detect power losses */ > +#define JZ_RTC_SCRATCHPAD_MAGIC 0x12345678 > + > #define JZ_RTC_WAKEUP_FILTER_MASK 0x0000FFE0 > #define JZ_RTC_RESET_COUNTER_MASK 0x00000FE0 > > @@ -134,10 +137,11 @@ static int jz4740_rtc_ctrl_set_bits(struct jz4740_rtc *rtc, uint32_t mask, > static int jz4740_rtc_read_time(struct device *dev, struct rtc_time *time) > { > struct jz4740_rtc *rtc = dev_get_drvdata(dev); > - uint32_t secs, secs2; > + uint32_t secs, secs2, magic; > int timeout = 5; > > - if (jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD) != 0x12345678) > + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); > + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) > return -EINVAL; > > /* If the seconds register is read while it is updated, it can contain a > @@ -169,7 +173,8 @@ static int jz4740_rtc_set_time(struct device *dev, struct rtc_time *time) > if (ret) > return ret; > > - return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, 0x12345678); > + return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, > + JZ_RTC_SCRATCHPAD_MAGIC); > } > > static int jz4740_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm) > @@ -307,6 +312,7 @@ static int jz4740_rtc_probe(struct platform_device *pdev) > struct jz4740_rtc *rtc; > unsigned long rate; > struct clk *clk; > + uint32_t magic; > int ret, irq; > > rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL); > @@ -369,6 +375,18 @@ static int jz4740_rtc_probe(struct platform_device *pdev) > /* Each 1 Hz pulse should happen after (rate) ticks */ > jz4740_rtc_reg_write(rtc, JZ_REG_RTC_REGULATOR, rate - 1); > > + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); > + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) { > + /* > + * If the scratchpad doesn't hold our magic value, then a > + * power loss occurred. Reset to Epoch. > + */ > + struct rtc_time time; > + > + rtc_time64_to_tm(0, &time); > + jz4740_rtc_set_time(dev, &time); Don't do that, this defeats the purpose of detecting when the power is lost. Returning a known bogus time is the worst thing you can do here. > + } > + > ret = devm_rtc_register_device(rtc->rtc); > if (ret) > return ret; > -- > 2.35.1 >
Hi Alexandre, Le mar., avril 19 2022 at 21:35:35 +0200, Alexandre Belloni <alexandre.belloni@bootlin.com> a écrit : > On 18/04/2022 19:49:31+0100, Paul Cercueil wrote: >> On power loss, reading the RTC value would fail as the scratchpad >> lost >> its magic value, until the hardware clock was set once again. >> >> To avoid that, reset the RTC value to Epoch in the probe if we >> detect >> that the scratchpad lost its magic value. >> >> Signed-off-by: Paul Cercueil <paul@crapouillou.net> >> --- >> drivers/rtc/rtc-jz4740.c | 24 +++++++++++++++++++++--- >> 1 file changed, 21 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/rtc/rtc-jz4740.c b/drivers/rtc/rtc-jz4740.c >> index 119baf168b32..aac5f68bf626 100644 >> --- a/drivers/rtc/rtc-jz4740.c >> +++ b/drivers/rtc/rtc-jz4740.c >> @@ -42,6 +42,9 @@ >> /* Magic value to enable writes on jz4780 */ >> #define JZ_RTC_WENR_MAGIC 0xA55A >> >> +/* Value written to the scratchpad to detect power losses */ >> +#define JZ_RTC_SCRATCHPAD_MAGIC 0x12345678 >> + >> #define JZ_RTC_WAKEUP_FILTER_MASK 0x0000FFE0 >> #define JZ_RTC_RESET_COUNTER_MASK 0x00000FE0 >> >> @@ -134,10 +137,11 @@ static int jz4740_rtc_ctrl_set_bits(struct >> jz4740_rtc *rtc, uint32_t mask, >> static int jz4740_rtc_read_time(struct device *dev, struct >> rtc_time *time) >> { >> struct jz4740_rtc *rtc = dev_get_drvdata(dev); >> - uint32_t secs, secs2; >> + uint32_t secs, secs2, magic; >> int timeout = 5; >> >> - if (jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD) != 0x12345678) >> + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); >> + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) >> return -EINVAL; >> >> /* If the seconds register is read while it is updated, it can >> contain a >> @@ -169,7 +173,8 @@ static int jz4740_rtc_set_time(struct device >> *dev, struct rtc_time *time) >> if (ret) >> return ret; >> >> - return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, >> 0x12345678); >> + return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, >> + JZ_RTC_SCRATCHPAD_MAGIC); >> } >> >> static int jz4740_rtc_read_alarm(struct device *dev, struct >> rtc_wkalrm *alrm) >> @@ -307,6 +312,7 @@ static int jz4740_rtc_probe(struct >> platform_device *pdev) >> struct jz4740_rtc *rtc; >> unsigned long rate; >> struct clk *clk; >> + uint32_t magic; >> int ret, irq; >> >> rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL); >> @@ -369,6 +375,18 @@ static int jz4740_rtc_probe(struct >> platform_device *pdev) >> /* Each 1 Hz pulse should happen after (rate) ticks */ >> jz4740_rtc_reg_write(rtc, JZ_REG_RTC_REGULATOR, rate - 1); >> >> + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); >> + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) { >> + /* >> + * If the scratchpad doesn't hold our magic value, then a >> + * power loss occurred. Reset to Epoch. >> + */ >> + struct rtc_time time; >> + >> + rtc_time64_to_tm(0, &time); >> + jz4740_rtc_set_time(dev, &time); > > Don't do that, this defeats the purpose of detecting when the power is > lost. Returning a known bogus time is the worst thing you can do here. So what is the best thing to do then? Cheers, -Paul >> + } >> + >> ret = devm_rtc_register_device(rtc->rtc); >> if (ret) >> return ret; >> -- >> 2.35.1 >> > > -- > Alexandre Belloni, co-owner and COO, Bootlin > Embedded Linux and Kernel engineering > https://bootlin.com
On 19/04/2022 20:48:54+0100, Paul Cercueil wrote: > Hi Alexandre, > > Le mar., avril 19 2022 at 21:35:35 +0200, Alexandre Belloni > <alexandre.belloni@bootlin.com> a écrit : > > On 18/04/2022 19:49:31+0100, Paul Cercueil wrote: > > > On power loss, reading the RTC value would fail as the scratchpad > > > lost > > > its magic value, until the hardware clock was set once again. > > > > > > To avoid that, reset the RTC value to Epoch in the probe if we > > > detect > > > that the scratchpad lost its magic value. > > > > > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > > > --- > > > drivers/rtc/rtc-jz4740.c | 24 +++++++++++++++++++++--- > > > 1 file changed, 21 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/rtc/rtc-jz4740.c b/drivers/rtc/rtc-jz4740.c > > > index 119baf168b32..aac5f68bf626 100644 > > > --- a/drivers/rtc/rtc-jz4740.c > > > +++ b/drivers/rtc/rtc-jz4740.c > > > @@ -42,6 +42,9 @@ > > > /* Magic value to enable writes on jz4780 */ > > > #define JZ_RTC_WENR_MAGIC 0xA55A > > > > > > +/* Value written to the scratchpad to detect power losses */ > > > +#define JZ_RTC_SCRATCHPAD_MAGIC 0x12345678 > > > + > > > #define JZ_RTC_WAKEUP_FILTER_MASK 0x0000FFE0 > > > #define JZ_RTC_RESET_COUNTER_MASK 0x00000FE0 > > > > > > @@ -134,10 +137,11 @@ static int jz4740_rtc_ctrl_set_bits(struct > > > jz4740_rtc *rtc, uint32_t mask, > > > static int jz4740_rtc_read_time(struct device *dev, struct > > > rtc_time *time) > > > { > > > struct jz4740_rtc *rtc = dev_get_drvdata(dev); > > > - uint32_t secs, secs2; > > > + uint32_t secs, secs2, magic; > > > int timeout = 5; > > > > > > - if (jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD) != 0x12345678) > > > + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); > > > + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) > > > return -EINVAL; > > > > > > /* If the seconds register is read while it is updated, it can > > > contain a > > > @@ -169,7 +173,8 @@ static int jz4740_rtc_set_time(struct device > > > *dev, struct rtc_time *time) > > > if (ret) > > > return ret; > > > > > > - return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, > > > 0x12345678); > > > + return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, > > > + JZ_RTC_SCRATCHPAD_MAGIC); > > > } > > > > > > static int jz4740_rtc_read_alarm(struct device *dev, struct > > > rtc_wkalrm *alrm) > > > @@ -307,6 +312,7 @@ static int jz4740_rtc_probe(struct > > > platform_device *pdev) > > > struct jz4740_rtc *rtc; > > > unsigned long rate; > > > struct clk *clk; > > > + uint32_t magic; > > > int ret, irq; > > > > > > rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL); > > > @@ -369,6 +375,18 @@ static int jz4740_rtc_probe(struct > > > platform_device *pdev) > > > /* Each 1 Hz pulse should happen after (rate) ticks */ > > > jz4740_rtc_reg_write(rtc, JZ_REG_RTC_REGULATOR, rate - 1); > > > > > > + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); > > > + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) { > > > + /* > > > + * If the scratchpad doesn't hold our magic value, then a > > > + * power loss occurred. Reset to Epoch. > > > + */ > > > + struct rtc_time time; > > > + > > > + rtc_time64_to_tm(0, &time); > > > + jz4740_rtc_set_time(dev, &time); > > > > Don't do that, this defeats the purpose of detecting when the power is > > lost. Returning a known bogus time is the worst thing you can do here. > > So what is the best thing to do then? > Well, -EINVAL is returned when the time is invalid, this should be enough. I'm not actually sure what is the issue you are trying to fix here. > Cheers, > -Paul > > > > + } > > > + > > > ret = devm_rtc_register_device(rtc->rtc); > > > if (ret) > > > return ret; > > > -- > > > 2.35.1 > > > > > > > -- > > Alexandre Belloni, co-owner and COO, Bootlin > > Embedded Linux and Kernel engineering > > https://bootlin.com > >
Le mar., avril 19 2022 at 22:00:32 +0200, Alexandre Belloni <alexandre.belloni@bootlin.com> a écrit : > On 19/04/2022 20:48:54+0100, Paul Cercueil wrote: >> Hi Alexandre, >> >> Le mar., avril 19 2022 at 21:35:35 +0200, Alexandre Belloni >> <alexandre.belloni@bootlin.com> a écrit : >> > On 18/04/2022 19:49:31+0100, Paul Cercueil wrote: >> > > On power loss, reading the RTC value would fail as the >> scratchpad >> > > lost >> > > its magic value, until the hardware clock was set once again. >> > > >> > > To avoid that, reset the RTC value to Epoch in the probe if we >> > > detect >> > > that the scratchpad lost its magic value. >> > > >> > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> >> > > --- >> > > drivers/rtc/rtc-jz4740.c | 24 +++++++++++++++++++++--- >> > > 1 file changed, 21 insertions(+), 3 deletions(-) >> > > >> > > diff --git a/drivers/rtc/rtc-jz4740.c >> b/drivers/rtc/rtc-jz4740.c >> > > index 119baf168b32..aac5f68bf626 100644 >> > > --- a/drivers/rtc/rtc-jz4740.c >> > > +++ b/drivers/rtc/rtc-jz4740.c >> > > @@ -42,6 +42,9 @@ >> > > /* Magic value to enable writes on jz4780 */ >> > > #define JZ_RTC_WENR_MAGIC 0xA55A >> > > >> > > +/* Value written to the scratchpad to detect power losses */ >> > > +#define JZ_RTC_SCRATCHPAD_MAGIC 0x12345678 >> > > + >> > > #define JZ_RTC_WAKEUP_FILTER_MASK 0x0000FFE0 >> > > #define JZ_RTC_RESET_COUNTER_MASK 0x00000FE0 >> > > >> > > @@ -134,10 +137,11 @@ static int >> jz4740_rtc_ctrl_set_bits(struct >> > > jz4740_rtc *rtc, uint32_t mask, >> > > static int jz4740_rtc_read_time(struct device *dev, struct >> > > rtc_time *time) >> > > { >> > > struct jz4740_rtc *rtc = dev_get_drvdata(dev); >> > > - uint32_t secs, secs2; >> > > + uint32_t secs, secs2, magic; >> > > int timeout = 5; >> > > >> > > - if (jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD) != >> 0x12345678) >> > > + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); >> > > + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) >> > > return -EINVAL; >> > > >> > > /* If the seconds register is read while it is updated, it >> can >> > > contain a >> > > @@ -169,7 +173,8 @@ static int jz4740_rtc_set_time(struct >> device >> > > *dev, struct rtc_time *time) >> > > if (ret) >> > > return ret; >> > > >> > > - return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, >> > > 0x12345678); >> > > + return jz4740_rtc_reg_write(rtc, JZ_REG_RTC_SCRATCHPAD, >> > > + JZ_RTC_SCRATCHPAD_MAGIC); >> > > } >> > > >> > > static int jz4740_rtc_read_alarm(struct device *dev, struct >> > > rtc_wkalrm *alrm) >> > > @@ -307,6 +312,7 @@ static int jz4740_rtc_probe(struct >> > > platform_device *pdev) >> > > struct jz4740_rtc *rtc; >> > > unsigned long rate; >> > > struct clk *clk; >> > > + uint32_t magic; >> > > int ret, irq; >> > > >> > > rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL); >> > > @@ -369,6 +375,18 @@ static int jz4740_rtc_probe(struct >> > > platform_device *pdev) >> > > /* Each 1 Hz pulse should happen after (rate) ticks */ >> > > jz4740_rtc_reg_write(rtc, JZ_REG_RTC_REGULATOR, rate - 1); >> > > >> > > + magic = jz4740_rtc_reg_read(rtc, JZ_REG_RTC_SCRATCHPAD); >> > > + if (magic != JZ_RTC_SCRATCHPAD_MAGIC) { >> > > + /* >> > > + * If the scratchpad doesn't hold our magic value, then a >> > > + * power loss occurred. Reset to Epoch. >> > > + */ >> > > + struct rtc_time time; >> > > + >> > > + rtc_time64_to_tm(0, &time); >> > > + jz4740_rtc_set_time(dev, &time); >> > >> > Don't do that, this defeats the purpose of detecting when the >> power is >> > lost. Returning a known bogus time is the worst thing you can do >> here. >> >> So what is the best thing to do then? >> > > Well, -EINVAL is returned when the time is invalid, this should be > enough. I'm not actually sure what is the issue you are trying to fix > here. htop fails to start and tells me: "No btime in /proc/stat: No such file or directory" until the date is reset. So I was assuming it was a case of the jz4740 driver not being correct and breaking userspace. Cheers, -Paul > >> Cheers, >> -Paul >> >> > > + } >> > > + >> > > ret = devm_rtc_register_device(rtc->rtc); >> > > if (ret) >> > > return ret; >> > > -- >> > > 2.35.1 >> > > >> > >> > -- >> > Alexandre Belloni, co-owner and COO, Bootlin >> > Embedded Linux and Kernel engineering >> > https://bootlin.com >> >> > > -- > Alexandre Belloni, co-owner and COO, Bootlin > Embedded Linux and Kernel engineering > https://bootlin.com
On 19/04/2022 21:53:17+0100, Paul Cercueil wrote: > > > So what is the best thing to do then? > > > > > > > Well, -EINVAL is returned when the time is invalid, this should be > > enough. I'm not actually sure what is the issue you are trying to fix > > here. > > htop fails to start and tells me: > "No btime in /proc/stat: No such file or directory" > > until the date is reset. So I was assuming it was a case of the jz4740 > driver not being correct and breaking userspace. > I guess either /proc/stat or htop needs fixing then ;) > Cheers, > -Paul > > > > > > > Cheers, > > > -Paul > > > > > > > > + } > > > > > + > > > > > ret = devm_rtc_register_device(rtc->rtc); > > > > > if (ret) > > > > > return ret; > > > > > -- > > > > > 2.35.1 > > > > > > > > > > > > > -- > > > > Alexandre Belloni, co-owner and COO, Bootlin > > > > Embedded Linux and Kernel engineering > > > > https://bootlin.com > > > > > > > > > > -- > > Alexandre Belloni, co-owner and COO, Bootlin > > Embedded Linux and Kernel engineering > > https://bootlin.com > >