[PATCH v3 4/7] rtc: spacemit: support the SpacemiT P1 RTC
Alexandre Belloni
alexandre.belloni at bootlin.com
Mon Jun 23 14:46:08 PDT 2025
On 23/06/2025 15:03:25-0500, Alex Elder wrote:
> On 6/23/25 2:14 PM, Alexandre Belloni wrote:
> > Hello,
> >
> > On 21/06/2025 22:29:36-0500, Alex Elder wrote:
> > > Add support for the RTC found in the SpacemiT P1 PMIC. Initially
> > > only setting and reading the time are supported.
> > >
> > > The PMIC is implemented as a multi-function device. This RTC is
> > > probed based on this driver being named in a MFD cell in the simple
> > > MFD I2C driver.
> > >
> > > Signed-off-by: Alex Elder <elder at riscstar.com>
> > > ---
> > > v3: - Added this driver to the series, in response to Lee Jones saying
> > > more than one MFD sub-device was required to be acceptable
> > >
> > > drivers/rtc/Kconfig | 10 ++++
> > > drivers/rtc/Makefile | 1 +
> > > drivers/rtc/rtc-p1.c | 137 +++++++++++++++++++++++++++++++++++++++++++
> >
> > We need something more descriptive than p1 here
>
> Are you referring to the chip itself, or do you want a longer
> file name? Do you prefer "rtc-spacemit-p1.c" or something?
Yes, this would be better, I feel like p1 is too short and is going to conflict
later on.
>
> > > 3 files changed, 148 insertions(+)
> > > create mode 100644 drivers/rtc/rtc-p1.c
> > >
> > > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > > index 9aec922613cec..27cff02ba4e66 100644
> > > --- a/drivers/rtc/Kconfig
> > > +++ b/drivers/rtc/Kconfig
> > > @@ -406,6 +406,16 @@ config RTC_DRV_MAX77686
> > > This driver can also be built as a module. If so, the module
> > > will be called rtc-max77686.
> > > +config RTC_DRV_P1
> >
> > Ditto
> >
> > > + tristate "SpacemiT P1 RTC"
> > > + depends on ARCH_SPACEMIT || COMPILE_TEST
> > > + select MFD_SPACEMIT_P1
> > > + default ARCH_SPACEMIT
> > > + help
> > > + Enable support for the RTC function in the SpacemiT P1 PMIC.
> > > + This driver can also be built as a module, which will be called
> > > + "spacemit-p1-rtc".
> > > +
> > > config RTC_DRV_NCT3018Y
> > > tristate "Nuvoton NCT3018Y"
> > > depends on OF
> > > diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> > > index 4619aa2ac4697..f8588426e2ba4 100644
> > > --- a/drivers/rtc/Makefile
> > > +++ b/drivers/rtc/Makefile
> > > @@ -171,6 +171,7 @@ obj-$(CONFIG_RTC_DRV_SD2405AL) += rtc-sd2405al.o
> > > obj-$(CONFIG_RTC_DRV_SD3078) += rtc-sd3078.o
> > > obj-$(CONFIG_RTC_DRV_SH) += rtc-sh.o
> > > obj-$(CONFIG_RTC_DRV_SNVS) += rtc-snvs.o
> > > +obj-$(CONFIG_RTC_DRV_P1) += rtc-p1.o
> > > obj-$(CONFIG_RTC_DRV_SPEAR) += rtc-spear.o
> > > obj-$(CONFIG_RTC_DRV_STARFIRE) += rtc-starfire.o
> > > obj-$(CONFIG_RTC_DRV_STK17TA8) += rtc-stk17ta8.o
> > > diff --git a/drivers/rtc/rtc-p1.c b/drivers/rtc/rtc-p1.c
> > > new file mode 100644
> > > index 0000000000000..e0d2c0c822142
> > > --- /dev/null
> > > +++ b/drivers/rtc/rtc-p1.c
> > > @@ -0,0 +1,137 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * Driver for the RTC found in the SpacemiT P1 PMIC
> > > + *
> > > + * Copyright (C) 2025 by RISCstar Solutions Corporation. All rights reserved.
> > > + */
> > > +
> > > +#include <linux/bits.h>
> > > +#include <linux/device.h>
> > > +#include <linux/module.h>
> > > +#include <linux/platform_device.h>
> > > +#include <linux/regmap.h>
> > > +#include <linux/rtc.h>
> > > +
> > > +#define MOD_NAME "spacemit-p1-rtc"
> > > +
> > > +/* Offset to byte containing the given time unit */
> > > +enum time_unit {
> > > + tu_second = 0, /* 0-59 */
> > > + tu_minute, /* 0-59 */
> > > + tu_hour, /* 0-59 */
> > > + tu_day, /* 0-30 (struct tm uses 1-31) */
> > > + tu_month, /* 0-11 */
> > > + tu_year, /* Years since 2000 (struct tm uses 1900) */
> > > + tu_count, /* Last; not a time unit */
> > > +};
> >
> > I'm not sure this enum actually brings anything
>
> It's just defining the sequence of register values
> symbolically. Do you prefer #defines?
>
> It doesn't matter much to me, I just want to know what
> you'd prefer.
Most of the drivers simply use the index number directly as the tm_* members are
descriptive enough.
>
> >
> > > +
> > > +/* Consecutive bytes contain seconds, minutes, etc. */
> > > +#define RTC_COUNT_BASE 0x0d
> > > +
> > > +#define RTC_CTRL 0x1d
> > > +#define RTC_EN BIT(2)
> > > +
> > > +struct p1_rtc {
> > > + struct regmap *regmap;
> > > + struct rtc_device *rtc;
> > > +};
> > > +
> > > +static int p1_rtc_read_time(struct device *dev, struct rtc_time *t)
> > > +{
> > > + struct p1_rtc *p1 = dev_get_drvdata(dev);
> > > + u8 time[tu_count];
> > > + int ret;
> > > +
> > > + ret = regmap_bulk_read(p1->regmap, RTC_COUNT_BASE, &time, sizeof(time));
> > > + if (ret)
> > > + return ret;
> > > +
> > > + t->tm_sec = time[tu_second] & GENMASK(5, 0);
> > > + t->tm_min = time[tu_minute] & GENMASK(5, 0);
> > > + t->tm_hour = time[tu_hour] & GENMASK(4, 0);
> > > + t->tm_mday = (time[tu_day] & GENMASK(4, 0)) + 1;
> > > + t->tm_mon = time[tu_month] & GENMASK(3, 0);
> > > + t->tm_year = (time[tu_year] & GENMASK(5, 0)) + 100;
> > > + /* tm_wday, tm_yday, and tm_isdst aren't used */
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static int p1_rtc_set_time(struct device *dev, struct rtc_time *t)
> > > +{
> > > + struct p1_rtc *p1 = dev_get_drvdata(dev);
> > > + u8 time[tu_count];
> > > + int ret;
> > > +
> > > + time[tu_second] = t->tm_sec;
> > > + time[tu_minute] = t->tm_min;
> > > + time[tu_hour] = t->tm_hour;
> > > + time[tu_day] = t->tm_mday - 1;
> > > + time[tu_month] = t->tm_mon;
> > > + time[tu_year] = t->tm_year - 100;
> > > +
> > > + /* Disable the RTC to update; re-enable again when done */
> > > + ret = regmap_update_bits(p1->regmap, RTC_CTRL, RTC_EN, 0);
> > > + if (ret)
> > > + return ret;
> > > +
> > > + ret = regmap_bulk_write(p1->regmap, RTC_COUNT_BASE, time, sizeof(time));
> > > +
> > > + (void)regmap_update_bits(p1->regmap, RTC_CTRL, RTC_EN, RTC_EN);
> >
> > Don't you care whether the RTC has been reenabled?
>
> Yes, Mateusz pointed this out. I'll fix this.
>
> I hope that disabling and re-enabling isn't require,
> which makes the error possibilities a lot simpler.
>
> Otherwise it's not clear how best to recover from
> an error re-enabling the RTC (but yes, if no error
> occurs in the bulk write, an error when re-enabling
> will be returned).
>
> > > +
> > > + return ret;
> > > +}
> > > +
> > > +static const struct rtc_class_ops p1_rtc_class_ops = {
> > > + .read_time = p1_rtc_read_time,
> > > + .set_time = p1_rtc_set_time,
> > > +};
> > > +
> > > +static int p1_rtc_probe(struct platform_device *pdev)
> > > +{
> > > + struct device *dev = &pdev->dev;
> > > + struct rtc_device *rtc;
> > > + struct p1_rtc *p1;
> > > + int ret;
> > > +
> > > + p1 = devm_kzalloc(dev, sizeof(*p1), GFP_KERNEL);
> > > + if (!p1)
> > > + return -ENOMEM;
> > > + dev_set_drvdata(dev, p1);
> > > +
> > > + p1->regmap = dev_get_regmap(dev->parent, NULL);
> > > + if (!p1->regmap)
> > > + return dev_err_probe(dev, -ENODEV, "failed to get regmap\n");
> > > +
> > > + rtc = devm_rtc_allocate_device(dev);
> > > + if (IS_ERR(rtc))
> > > + return dev_err_probe(dev, PTR_ERR(rtc),
> > > + "error allocating device\n");
> > > + p1->rtc = rtc;
> > > +
> > > + rtc->ops = &p1_rtc_class_ops;
> > > + rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
> > > + rtc->range_max = RTC_TIMESTAMP_END_2063;
> > > +
> > > + clear_bit(RTC_FEATURE_ALARM, rtc->features);
> > > + clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
> > > +
> > > + ret = devm_rtc_register_device(rtc);
> > > + if (ret)
> > > + return dev_err_probe(dev, ret, "error registering RTC\n");
> >
> > This message is unnecessary, there are no silent error path in
> > devm_rtc_register_device
>
> Awesome. I'll just return what devm_rtc_regsister_device()
> returns.
>
> Thanks a lot.
>
> -Alex
>
> >
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static struct platform_driver p1_rtc_driver = {
> > > + .probe = p1_rtc_probe,
> > > + .driver = {
> > > + .name = MOD_NAME,
> > > + },
> > > +};
> > > +
> > > +module_platform_driver(p1_rtc_driver);
> > > +
> > > +MODULE_DESCRIPTION("SpacemiT P1 RTC driver");
> > > +MODULE_LICENSE("GPL");
> > > +MODULE_ALIAS("platform:" MOD_NAME);
> >
>
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
More information about the linux-riscv
mailing list