Re: [PATCH INTERNAL v1 1/3] rtc: tps6594: add driver for TPS6594 PMIC RTC

Alexandre Belloni
2023-03-07T11:11:51Z

Hello,

On 24/02/2023 14:31:27+0100, Esteban Blanc wrote:
> +struct tps6594_rtc {
> + struct rtc_device *rtc;
> +};

Is the struct actually useful?

> +/* Pulse GET_TIME field of RTC_CTRL_1 to store a timestamp in shadow registers */
> +static int tps6594_rtc_shadow_timestamp(struct device *dev, struct tps6594 *tps)
> +{
> + int ret;
> +
> + /* Set GET_TIME to 0. This way, next time we set GET_TIME to 1 we are sure to store an
> + * up-to-date timestamp
> + */
> + ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
> + TPS6594_BIT_GET_TIME);
> + if (ret < 0) {
> + dev_err(dev, "RTC CTRL1 reg update failed with err:%d\n", ret);

This is very verbose and the user doesn't have any meaningful action
once this happens. Either remove the dev_err or convert them to dev_dbg.

> + return ret;
> + }
> +
> + /* Copy content of RTC registers to shadow registers or latches to read a coherent
> + * timestamp
> + */
> + ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
> + TPS6594_BIT_GET_TIME);
> + if (ret < 0) {
> + dev_err(dev, "RTC CTRL1 reg update failed with err:%d\n", ret);
> + return ret;
> + }
> +
> + return ret;
> +}
> +
> +/*
> + * Gets current tps6594 RTC time and date parameters.
> + *
> + * The RTC's time/alarm representation is not what gmtime(3) requires
> + * Linux to use:
> + *
> + * - Months are 1..12 vs Linux 0-11
> + * - Years are 0..99 vs Linux 1900..N (we assume 21st century)
> + */

I don't find this comment to be particularly useful.

> +static int tps6594_rtc_read_time(struct device *dev, struct rtc_time *tm)
> +{
> + unsigned char rtc_data[NUM_TIME_REGS];
> + struct tps6594 *tps = dev_get_drvdata(dev->parent);
> + int ret;
> +

You could check whether the RTC is actually started here and return
-EINVAL if this is not the case.

> + ret = tps6594_rtc_shadow_timestamp(dev, tps);
> + if (ret < 0) {
> + dev_err(dev,
> + "failed to store a timestamp in shadow registers:%d\n",
> + ret);
> + return ret;
> + }
> +
> + /* Read shadowed RTC registers */
> + ret = regmap_bulk_read(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
> + NUM_TIME_REGS);
> + if (ret < 0) {
> + dev_err(dev, "rtc_read_time failed with error :%d\n", ret);
> + return ret;
> + }
> +
> + tm->tm_sec = bcd2bin(rtc_data[0]);
> + tm->tm_min = bcd2bin(rtc_data[1]);
> + tm->tm_hour = bcd2bin(rtc_data[2]);
> + tm->tm_mday = bcd2bin(rtc_data[3]);
> + tm->tm_mon = bcd2bin(rtc_data[4]) - 1;
> + tm->tm_year = bcd2bin(rtc_data[5]) + 100;
> + tm->tm_wday = bcd2bin(rtc_data[6]);
> +
> + return ret;
> +}
> +
> +/*
> + * Sets current tps6594 RTC time and date parameters.
> + *
> + * The RTC's time/alarm representation is not what gmtime(3) requires
> + * Linux to use:
> + *
> + * - Months are 1..12 vs Linux 0-11
> + * - Years are 0..99 vs Linux 1900..N (we assume 21st century)
> + */

Ditto

> +static int tps6594_rtc_set_time(struct device *dev, struct rtc_time *tm)
> +{
> + unsigned char rtc_data[NUM_TIME_REGS];
> + struct tps6594 *tps = dev_get_drvdata(dev->parent);
> + int ret;
> +
> + rtc_data[0] = bin2bcd(tm->tm_sec);
> + rtc_data[1] = bin2bcd(tm->tm_min);
> + rtc_data[2] = bin2bcd(tm->tm_hour);
> + rtc_data[3] = bin2bcd(tm->tm_mday);
> + rtc_data[4] = bin2bcd(tm->tm_mon + 1);
> + rtc_data[5] = bin2bcd(tm->tm_year - 100);
> + rtc_data[6] = bin2bcd(tm->tm_wday);
> +
> + /* Stop RTC while updating the RTC time registers */
> + ret = regmap_clear_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
> + TPS6594_BIT_STOP_RTC);
> + if (ret < 0) {
> + dev_err(dev, "RTC stop failed: %d\n", ret);
> + return ret;
> + }
> +
> + /* Update all the time registers in one shot */
> + ret = regmap_bulk_write(tps->regmap, TPS6594_REG_RTC_SECONDS, rtc_data,
> + NUM_TIME_REGS);
> + if (ret < 0) {
> + dev_err(dev, "rtc_set_time failed: %d\n", ret);
> + return ret;
> + }
> +
> + /* Start back RTC */
> + ret = regmap_set_bits(tps->regmap, TPS6594_REG_RTC_CTRL_1,
> + TPS6594_BIT_STOP_RTC);
> + if (ret < 0)
> + dev_err(dev, "RTC start failed: %d\n", ret);
> +
> + return ret;
> +}
> +

> +static int tps6594_rtc_probe(struct platform_device *pdev)
> +{
> + struct tps6594 *tps6594;
> + struct tps6594_rtc *tps_rtc;
> + int irq;
> + int ret;
> +
> + tps6594 = dev_get_drvdata(pdev->dev.parent);
> +
> + tps_rtc = devm_kzalloc(&pdev->dev, sizeof(struct tps6594_rtc),
> + GFP_KERNEL);
> + if (!tps_rtc)
> + return -ENOMEM;
> +
> + tps_rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
> + if (IS_ERR(tps_rtc->rtc))
> + return PTR_ERR(tps_rtc->rtc);
> +
> + /* Enable crystal oscillator */
> + ret = regmap_set_bits(tps6594->regmap, TPS6594_REG_RTC_CTRL_2,
> + TPS6594_BIT_XTAL_EN);
> + if (ret < 0)
> + return ret;
> +
> + /* Start rtc */
> + ret = regmap_set_bits(tps6594->regmap, TPS6594_REG_RTC_CTRL_1,
> + TPS6594_BIT_STOP_RTC);
> + if (ret < 0)
> + return ret;

Do that (XTAL_EN and clearing STOP) only once the time is known to be
set to a correct value so read_time doesn't have a chance to return a
bogus value.

> +
> + mdelay(100);
> +
> + /*
> + * RTC should be running now. Check if this is the case.
> + * If not it might be a missing oscillator.
> + */
> + ret = regmap_test_bits(tps6594->regmap, TPS6594_REG_RTC_STATUS,
> + TPS6594_BIT_RUN);
> + if (ret < 0)
> + return ret;
> + if (ret == 0)
> + return -ENODEV;
> +
> + platform_set_drvdata(pdev, tps_rtc);
> +
> + irq = platform_get_irq_byname(pdev, TPS6594_IRQ_NAME_ALARM);
> + if (irq < 0) {
> + dev_err(&pdev->dev, "Failed to get irq\n");
> + return irq;
> + }
> +
> + ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
> + tps6594_rtc_interrupt, IRQF_ONESHOT,
> + TPS6594_IRQ_NAME_ALARM, &pdev->dev);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "Failed to request_threaded_irq\n");
> + return ret;
> + }
> +
> + tps_rtc->rtc->ops = &tps6594_rtc_ops;
> + tps_rtc->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
> + tps_rtc->rtc->range_max = RTC_TIMESTAMP_END_2099;
> +
> + return devm_rtc_register_device(tps_rtc->rtc);
> +}
> +
> +static struct platform_driver tps6594_rtc_driver = {
> + .probe = tps6594_rtc_probe,
> + .driver = {
> + .name = "tps6594-rtc",
> + },
> +};
> +
> +module_platform_driver(tps6594_rtc_driver);
> +
> +MODULE_ALIAS("platform:tps6594-rtc");
> +MODULE_AUTHOR("Esteban Blanc <eblanc@baylibre.com>");
> +MODULE_DESCRIPTION("TPS6594 RTC driver");
> +MODULE_LICENSE("GPL");
> --
> 2.38.1
>

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