Re: [PATCH 2/3] rtc: Add support for the MSTAR MSC313 RTC

Romain Perier
2021-07-21T16:56:53Z

Hello Alexandre,

Le mar. 20 juil. 2021 à 22:01, Alexandre Belloni
<alexandre.belloni@bootlin.com> a écrit :
>
> Hello Romain,
>
> On 20/07/2021 19:22:50+0200, Romain Perier wrote:
> > From: Daniel Palmer <daniel@0x0f.com>
> >
> > This adds support for the RTC block on the Mstar MSC313e SoCs and newer.
> >
> > Signed-off-by: Daniel Palmer <daniel@0x0f.com>
> > Co-developed-by: Romain Perier <romain.perier@gmail.com>
> > Signed-off-by: Romain Perier <romain.perier@gmail.com>
> > ---
> > MAINTAINERS | 1 +
> > drivers/rtc/Kconfig | 10 ++
> > drivers/rtc/Makefile | 1 +
> > drivers/rtc/rtc-msc313.c | 246 +++++++++++++++++++++++++++++++++++++++
> > 4 files changed, 258 insertions(+)
> > create mode 100644 drivers/rtc/rtc-msc313.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 6c8be735cc91..7e8d1a375e0d 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -2220,6 +2220,7 @@ F: arch/arm/boot/dts/mstar-*
> > F: arch/arm/mach-mstar/
> > F: drivers/clk/mstar/
> > F: drivers/gpio/gpio-msc313.c
> > +F: drivers/rtc/rtc-msc313.c
> > F: drivers/watchdog/msc313e_wdt.c
> > F: include/dt-bindings/clock/mstar-*
> > F: include/dt-bindings/gpio/msc313-gpio.h
> > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > index 12153d5801ce..67870b422bc5 100644
> > --- a/drivers/rtc/Kconfig
> > +++ b/drivers/rtc/Kconfig
> > @@ -1925,4 +1925,14 @@ config RTC_DRV_WILCO_EC
> > This can also be built as a module. If so, the module will
> > be named "rtc_wilco_ec".
> >
> > +config RTC_DRV_MSC313
> > + tristate "MStar MSC313 RTC"
> > + depends on ARCH_MSTARV7
>
> || COMPILE_TEST maybe ?

Arf, I always forget this option. Ack, I will add it in v2.

>
> > + help
> > + If you say yes here you get support for the Mstar MSC313e On-Chip
> > + Real Time Clock.
> > +
> > + This driver can also be built as a module, if so, the module
> > + will be called "rtc-msc313".
> > +
> > endif # RTC_CLASS
>
>
> > +static int msc313_rtc_read_time(struct device *dev, struct rtc_time *tm)
> > +{
> > + struct msc313_rtc *priv = dev_get_drvdata(dev);
> > + u32 seconds;
> > + u16 reg;
> > +
> > + reg = readw(priv->rtc_base + REG_RTC_CTRL);
> > + writew(reg | READ_EN_BIT, priv->rtc_base + REG_RTC_CTRL);
> > +
> > + /* Wait for HW latch done */
> > + while (readw(priv->rtc_base + REG_RTC_CTRL) & READ_EN_BIT)
> > + udelay(1);
> > +
> > + seconds = readw(priv->rtc_base + REG_RTC_CNT_VAL_L)
> > + | (readw(priv->rtc_base + REG_RTC_CNT_VAL_H) << 16);
> > +
> > + rtc_time64_to_tm(seconds, tm);
> > +
> > + return rtc_valid_tm(tm);
>
> This is not necessary, tm is valid at that point (and the core will
> check anyway).

ack.

>
> > +}
> > +
> > +static int msc313_rtc_set_time(struct device *dev, struct rtc_time *tm)
> > +{
> > + struct msc313_rtc *priv = dev_get_drvdata(dev);
> > + unsigned long seconds;
> > + u16 reg;
> > +
> > + seconds = rtc_tm_to_time64(tm);
> > + writew(seconds & 0xFFFF, priv->rtc_base + REG_RTC_LOAD_VAL_L);
> > + writew((seconds >> 16) & 0xFFFF, priv->rtc_base + REG_RTC_LOAD_VAL_H);
> > + reg = readw(priv->rtc_base + REG_RTC_CTRL);
> > + writew(reg | LOAD_EN_BIT, priv->rtc_base + REG_RTC_CTRL);
> > +
> > + /* need to check carefully if we want to clear REG_RTC_LOAD_VAL_H for customer*/
> > + while (readw(priv->rtc_base + REG_RTC_CTRL) & LOAD_EN_BIT)
> > + udelay(1);
> > + writew(0, priv->rtc_base + REG_RTC_LOAD_VAL_H);
>
> Why is that necessary? The comment is not super useful here.
>
> > +
> > + return 0;
> > +}
> > +
> > +static const struct rtc_class_ops msc313_rtc_ops = {
> > + .read_time = msc313_rtc_read_time,
> > + .set_time = msc313_rtc_set_time,
> > + .read_alarm = msc313_rtc_read_alarm,
> > + .set_alarm = msc313_rtc_set_alarm,
> > + .alarm_irq_enable = msc313_rtc_alarm_irq_enable,
> > +};
> > +
> > +static irqreturn_t msc313_rtc_interrupt(s32 irq, void *dev_id)
> > +{
> > + struct msc313_rtc *priv = dev_get_drvdata(dev_id);
> > + u16 reg;
> > +
> > + reg = readw_relaxed(priv->rtc_base + REG_RTC_CTRL);
> > + reg |= INT_CLEAR_BIT;
> > + reg &= ~INT_FORCE_BIT;
> > + writew_relaxed(reg, priv->rtc_base + REG_RTC_CTRL);
> > +
>
> I'm not convinced the _relaxed functions are doing the right thing here.

Good catch for the _relaxed, I did not pay attention during refactoring.

> Also, shouldn't you check the alarm actually fired?

You mean before set the flag "RTC_AF" ? This driver is mostly based on
reverse engineering,
even if we have some hardware info. I will try to find if it is
possible (I mean, from the info
I have).

>
> > + rtc_update_irq(priv->rtc_dev, 1, RTC_IRQF | RTC_AF);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static int msc313_rtc_remove(struct platform_device *pdev)
> > +{
> > + struct msc313_rtc *priv = platform_get_drvdata(pdev);
> > +
> > + clk_disable_unprepare(priv->clk);
>
> With a nice devm_add_action_or_reset() in the probe, you can remove the
> need for msc313_rtc_remove().

devm_add_action_or_reset() you said, interesting I did not know this function.

>
> > +
> > + return 0;
> > +}
> > +
> > +static int msc313_rtc_probe(struct platform_device *pdev)
> > +{
> > + struct device *dev = &pdev->dev;
> > + struct msc313_rtc *priv;
> > + int ret;
> > + int irq;
> > + unsigned long rate;
> > + u16 reg;
> > +
> > + priv = devm_kzalloc(&pdev->dev, sizeof(struct msc313_rtc), GFP_KERNEL);
> > + if (!priv)
> > + return -ENOMEM;
> > +
> > + priv->rtc_base = devm_platform_ioremap_resource(pdev, 0);
> > + if (IS_ERR(priv->rtc_base))
> > + return PTR_ERR(priv->rtc_base);
> > +
> > + irq = platform_get_irq(pdev, 0);
> > + if (irq < 0)
> > + return -EINVAL;
> > +
> > + ret = devm_request_irq(dev, irq, msc313_rtc_interrupt, IRQF_SHARED,
> > + dev_name(&pdev->dev), &pdev->dev);
> > + if (ret) {
> > + dev_err(dev, "Unable to request irq\n");
> > + return ret;
> > + }
> > +
> > + priv->clk = devm_clk_get(dev, NULL);
> > + if (IS_ERR(priv->clk)) {
> > + dev_err(dev, "No input reference clock\n");
> > + return PTR_ERR(priv->clk);
> > + }
> > +
> > + ret = clk_prepare_enable(priv->clk);
> > + if (ret) {
> > + dev_err(dev, "Failed to enable the reference clock, %d\n", ret);
> > + return ret;
> > + }
> > +
> > + rate = clk_get_rate(priv->clk);
> > +
> > + reg = readw(priv->rtc_base + REG_RTC_CTRL);
> > + if (!(reg & SOFT_RSTZ_BIT)) {
> > + reg |= SOFT_RSTZ_BIT;
> > + writew(reg, priv->rtc_base + REG_RTC_CTRL);
> > + }
>
> What is the meaning of this bit? I would think it is better to use that
> to know whether the RTC holds the correct time instead of killing the
> info here.
>
> > +
> > + writew(rate & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_L);
> > + writew((rate >> 16) & 0xFFFF, priv->rtc_base + REG_RTC_FREQ_CW_H);
> > +
> > + reg |= CNT_EN_BIT;
> > + writew(reg, priv->rtc_base + REG_RTC_CTRL);
> > +
> > + platform_set_drvdata(pdev, priv);
> > +
> > + priv->rtc_dev = devm_rtc_device_register(dev, dev_name(dev), &msc313_rtc_ops, THIS_MODULE);
> > + if (IS_ERR(priv->rtc_dev)) {
> > + dev_err(dev, "Failed to register rtc device\n");
> > + return PTR_ERR(priv->rtc_dev);
> > + }
>
> Please switch to devm_rtc_allocate_device and devm_rtc_register_device.
> Also drop the error message, it is not necessary.
>
> You must also set the RTC range. To help you, you can use:
> https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/rtc-tools.git/tree/rtc-range.c
> then you must update the DT bindings as the RTC will support the
> start-year property
>
> You must also run rtctest and should include the results.

Ack, I will do this in v2.

Thanks!