Re: [PATCH v8 5/8] rtc: spacemit: support the SpacemiT P1 RTC

Alexandre Belloni
2025-07-23T21:40:07Z

On 10/07/2025 12:51:03-0500, Alex Elder wrote:
> +static int p1_rtc_read_time(struct device *dev, struct rtc_time *t)
> +{
> + struct p1_rtc *p1 = dev_get_drvdata(dev);
> + struct regmap *regmap = p1->regmap;
> + u32 count = RTC_READ_TRIES;
> + u8 seconds;
> + u8 time[6];
> + int ret;
> +
> + if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN))
> + return -ENODEV; /* RTC is disabled */

That should be -EINVAL, as all the other drivers have standardized this.

With this fixed,
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> +
> + ret = regmap_bulk_read(regmap, RTC_TIME, time, sizeof(time));
> + if (ret)
> + return ret;
> +
> + do {
> + seconds = time[0];
> + ret = regmap_bulk_read(regmap, RTC_TIME, time, sizeof(time));
> + if (ret)
> + return ret;
> + } while (time[0] != seconds && --count);
> +
> + if (!count)
> + return -EIO; /* Unable to get a consistent result */
> +
> + t->tm_sec = time[0] & GENMASK(5, 0);
> + t->tm_min = time[1] & GENMASK(5, 0);
> + t->tm_hour = time[2] & GENMASK(4, 0);
> + t->tm_mday = (time[3] & GENMASK(4, 0)) + 1;
> + t->tm_mon = time[4] & GENMASK(3, 0);
> + t->tm_year = (time[5] & GENMASK(5, 0)) + 100;
> +
> + return 0;
> +}
> +
> +/*
> + * The P1 hardware documentation states that values in the registers are
> + * latched so when written they represent a consistent time snapshot.
> + * Nevertheless, this is not guaranteed by the implementation, so we must
> + * disable the RTC while updating it.
> + */
> +static int p1_rtc_set_time(struct device *dev, struct rtc_time *t)
> +{
> + struct p1_rtc *p1 = dev_get_drvdata(dev);
> + struct regmap *regmap = p1->regmap;
> + u8 time[6];
> + int ret;
> +
> + time[0] = t->tm_sec;
> + time[1] = t->tm_min;
> + time[2] = t->tm_hour;
> + time[3] = t->tm_mday - 1;
> + time[4] = t->tm_mon;
> + time[5] = t->tm_year - 100;
> +
> + /* Disable the RTC to update; re-enable again when done */
> + ret = regmap_clear_bits(regmap, RTC_CTRL, RTC_EN);
> + if (ret)
> + return ret;
> +
> + /* If something goes wrong, leave the RTC disabled */
> + ret = regmap_bulk_write(regmap, RTC_TIME, time, sizeof(time));
> + if (ret)
> + return ret;
> +
> + return regmap_set_bits(regmap, RTC_CTRL, RTC_EN);
> +}
> +
> +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;
> +
> + 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);
> +
> + return devm_rtc_register_device(rtc);
> +}
> +
> +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);
> --
> 2.45.2
>

--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering