Message-ID: <87r09q7gpm.fsf@geanix.com>
Date: Wed, 11 Sep 2024 10:11:17 +0200
From: Esben Haabendal <esben@...nix.com>
To: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
  linux-rtc@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] rtc: isl12022: Add alarm support

Rasmus Villemoes <linux@...musvillemoes.dk> writes:

> Esben Haabendal <esben@...nix.com> writes:
>
>> The ISL12022 RTC has a combined INT/fOUT pin, which can be used for alarm
>> interrupt when frequency output is not enabled.
>>
>> The device-tree bindings should ensure that interrupt and clock output is
>> not enabled at the same time.
>>
>> Signed-off-by: Esben Haabendal <esben@...nix.com>
>> ---
>>  drivers/rtc/rtc-isl12022.c | 244 ++++++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 241 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/rtc/rtc-isl12022.c b/drivers/rtc/rtc-isl12022.c
>> index d82278fdc29b..682b1bf10160 100644
>> --- a/drivers/rtc/rtc-isl12022.c
>> +++ b/drivers/rtc/rtc-isl12022.c
>> @@ -21,7 +21,7 @@
>>  
>>  #include <asm/byteorder.h>
>>  
>> -/* ISL register offsets */
>> +/* RTC - Real time clock registers */
>>  #define ISL12022_REG_SC		0x00
>>  #define ISL12022_REG_MN		0x01
>>  #define ISL12022_REG_HR		0x02
>> @@ -30,21 +30,36 @@
>>  #define ISL12022_REG_YR		0x05
>>  #define ISL12022_REG_DW		0x06
>>  
>> +/* CSR - Control and status registers */
>>  #define ISL12022_REG_SR		0x07
>>  #define ISL12022_REG_INT	0x08
>> -
>>  #define ISL12022_REG_PWR_VBAT	0x0a
>> -
>>  #define ISL12022_REG_BETA	0x0d
>> +
>> +/* ALARM - Alarm registers */
>> +#define ISL12022_REG_SCA0	0x10
>> +#define ISL12022_REG_MNA0	0x11
>> +#define ISL12022_REG_HRA0	0x12
>> +#define ISL12022_REG_DTA0	0x13
>> +#define ISL12022_REG_MOA0	0x14
>> +#define ISL12022_REG_DWA0	0x15
>> +#define ISL12022_ALARM_SECTION		ISL12022_REG_SCA0
>> +#define ISL12022_ALARM_SECTION_LEN	(ISL12022_REG_DWA0 - ISL12022_REG_SCA0 + 1)
>> +
>> +/* TEMP - Temperature sensor registers */
>>  #define ISL12022_REG_TEMP_L	0x28
>>  
>>  /* ISL register bits */
>>  #define ISL12022_HR_MIL		(1 << 7)	/* military or 24 hour time */
>>  
>> +#define ISL12022_SR_ALM		(1 << 4)
>>  #define ISL12022_SR_LBAT85	(1 << 2)
>>  #define ISL12022_SR_LBAT75	(1 << 1)
>>  
>> +#define ISL12022_INT_ARST	(1 << 7)
>>  #define ISL12022_INT_WRTC	(1 << 6)
>> +#define ISL12022_INT_IM		(1 << 5)
>> +#define ISL12022_INT_FOBATB	(1 << 4)
>>  #define ISL12022_INT_FO_MASK	GENMASK(3, 0)
>>  #define ISL12022_INT_FO_OFF	0x0
>>  #define ISL12022_INT_FO_32K	0x1
>> @@ -52,10 +67,18 @@
>>  #define ISL12022_REG_VB85_MASK	GENMASK(5, 3)
>>  #define ISL12022_REG_VB75_MASK	GENMASK(2, 0)
>>  
>> +#define ISL12022_ALARM_ENABLE	(1 << 7)	/* for all ALARM registers  */
>> +
>>  #define ISL12022_BETA_TSE	(1 << 7)
>>  
>> +static struct i2c_driver isl12022_driver;
>> +
>>  struct isl12022 {
>> +	struct i2c_client *i2c;
>> +	struct rtc_device *rtc;
>>  	struct regmap *regmap;
>> +	int irq;
>> +	bool irq_enabled;
>>  };
>>  
>>  static umode_t isl12022_hwmon_is_visible(const void *data,
>> @@ -215,6 +238,208 @@ static int isl12022_rtc_set_time(struct device *dev, struct rtc_time *tm)
>>  	return regmap_bulk_write(regmap, ISL12022_REG_SC, buf, sizeof(buf));
>>  }
>>  
>> +static int isl12022_rtc_read_alarm(struct device *dev,
>> +				   struct rtc_wkalrm *alarm)
>> +{
>
> Style nit, but I think it's easier to read and grep for if the prototype
> is on one line, and it wouldn't go significantly over 80 chars. The file
> already has a few lines > 80 chars, and the 80 char limit doesn't really
> exist anymore.

Ok. I will change it to a single line. No problem.

>
>> 
>> +	struct rtc_time *const tm = &alarm->time;
>
> Hm, declaring auto variables const is quite unusual. I see that a few
> other rtc drivers have done this, but I don't it's an example to copy.

Ok. Dropping the const here. And yes, it had crept via copy-paste.

>> +	struct isl12022 *isl12022 = dev_get_drvdata(dev);
>> +	struct regmap *regmap = isl12022->regmap;
>> +	uint8_t buf[ISL12022_ALARM_SECTION_LEN];
>
> The kernel normally says u8 (and you do as well in _set_alarm()).

Another copy-paste issue. This time it was from _read_time() and
_set_time().

To avoid inconsistent coding style, I guess I should add a commit
changing to u8 in _read_time() and _set_time() as well.

>> +	int ret, yr, i;
>> +
>> +	ret = regmap_bulk_read(regmap, ISL12022_ALARM_SECTION,
>> +			       buf, sizeof(buf));
>> +	if (ret) {
>> +		dev_err(dev, "%s: reading ALARM registers failed\n",
>> +			__func__);
>> +		return ret;
>> +	}
>> +
>> +	dev_dbg(dev,
>> +		"%s: sc=%02x, mn=%02x, hr=%02x, dt=%02x, mo=%02x, dw=%02x\n",
>> +		__func__, buf[0], buf[1], buf[2], buf[3], buf[4], buf[5]);
>> +
>> +	tm->tm_sec = bcd2bin(buf[ISL12022_REG_SCA0 - ISL12022_ALARM_SECTION]
>> +			     & 0x7F);
>> +	tm->tm_min = bcd2bin(buf[ISL12022_REG_MNA0 - ISL12022_ALARM_SECTION]
>> +			     & 0x7F);
>> +	tm->tm_hour = bcd2bin(buf[ISL12022_REG_HRA0 - ISL12022_ALARM_SECTION]
>> +			      & 0x3F);
>> +	tm->tm_mday = bcd2bin(buf[ISL12022_REG_DTA0 - ISL12022_ALARM_SECTION]
>> +			      & 0x3F);
>> +	tm->tm_mon = bcd2bin(buf[ISL12022_REG_MOA0 - ISL12022_ALARM_SECTION]
>> +			     & 0x1F) - 1;
>> +	tm->tm_wday = buf[ISL12022_REG_DWA0 - ISL12022_ALARM_SECTION] & 0x07;
>> +
>
> Here I'd also suggest keeping each assignment on one line, it's rather
> hard to read this way.

I agree, and I will change it here. But if the 80 columns rule is out,
what kind of rule for line width is used instead?

>> +	/* The alarm doesn't store the year so get it from the rtc section */
>> +	ret = regmap_read(regmap, ISL12022_REG_YR, &yr);
>> +	if (ret) {
>> +		dev_err(dev, "%s: reading YR register failed\n", __func__);
>> +		return yr;
>
> return ret, presumably.

Oops. Fixing.

> regmap_read() takes an 'unsigned int *', but yr is int. If the compiler
> doesn't warn I suppose it doesn't matter.

My compiler seems happy. But no harm in fixing it.

> I suggest moving the reading of the yr register up to right after the
> other regmap_read, then you could also include it in the dev_dbg output,
> and all the bcd2bin() conversions are done next to each other.
>
>> +	}
>> +	tm->tm_year = bcd2bin(yr) + 100;
>> +
>> +	for (i = 0 ; i < ISL12022_ALARM_SECTION_LEN ; i++) {
>
> Nit: no spaces before the semicolons.

Nit removal in progress.

>> +		if (buf[i] & ISL12022_ALARM_ENABLE) {
>> +			alarm->enabled = 1;
>> +			break;
>> +		}
>> +	}
>> +
>> +	dev_dbg(dev, "%s: %ptR\n", __func__, tm);
>> +
>> +	return 0;
>> +}
>> +
>> +static int isl12022_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
>> +{
>> +	struct rtc_time *alarm_tm = &alarm->time;
>> +	struct isl12022 *isl12022 = dev_get_drvdata(dev);
>> +	struct regmap *regmap = isl12022->regmap;
>> +	u8 regs[ISL12022_ALARM_SECTION_LEN] = { 0, };
>> +	struct rtc_time rtc_tm;
>> +	int ret = 0, enable, dw;
>> +
>
> Nit: No need to initialize ret when the very first thing you do is
> assigning to it.

Fixing.

>> +	ret = isl12022_rtc_read_time(dev, &rtc_tm);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/* If the alarm time is before the current time disable the alarm */
>> +	if (!alarm->enabled || rtc_tm_sub(alarm_tm, &rtc_tm) <= 0)
>> +		enable = 0;
>> +	else
>> +		enable = ISL12022_ALARM_ENABLE;
>> +
>> +	/* Set non-matching tm_wday to safeguard against early false matching
>> +	 * while setting all the alarm registers (this rtc lacks a general
>> +	 * alarm/irq enable/disable bit).
>> +	 */
>
> Nit: Don't use network comment style.

Ok. I did not know this was network comment style only.
So it should be with both '/*' and '*/' on separate lines?

>> +	if (enable) {
>> +		ret = regmap_read(regmap, ISL12022_REG_DW, &dw);
>> +		if (ret) {
>> +			dev_err(dev, "%s: reading DW failed\n", __func__);
>> +			return ret;
>> +		}
>> +		/* ~4 days into the future should be enough to avoid match */
>> +		dw = ((dw + 4) % 7) | ISL12022_ALARM_ENABLE;
>> +		ret = regmap_write(regmap, ISL12022_REG_DWA0, dw);
>> +		if (ret) {
>> +			dev_err(dev, "%s: writing DWA0 failed\n", __func__);
>> +			return ret;
>> +		}
>> +	}
>> +
>> +	/* Program the alarm and enable it for each setting */
>> +	regs[ISL12022_REG_SCA0 - ISL12022_ALARM_SECTION] =
>> +		bin2bcd(alarm_tm->tm_sec) | enable;
>> +	regs[ISL12022_REG_MNA0 - ISL12022_ALARM_SECTION] =
>> +		bin2bcd(alarm_tm->tm_min) | enable;
>> +	regs[ISL12022_REG_HRA0 - ISL12022_ALARM_SECTION] =
>> +		bin2bcd(alarm_tm->tm_hour) | enable;
>> +	regs[ISL12022_REG_DTA0 - ISL12022_ALARM_SECTION] =
>> +		bin2bcd(alarm_tm->tm_mday) | enable;
>> +	regs[ISL12022_REG_MOA0 - ISL12022_ALARM_SECTION] =
>> +		bin2bcd(alarm_tm->tm_mon + 1) | enable;
>> +	regs[ISL12022_REG_DWA0 - ISL12022_ALARM_SECTION] =
>> +		bin2bcd(alarm_tm->tm_wday & 7) | enable;
>> +
>
> The dwa0 handling is a nice trick for avoiding triggering a false
> alarm. But I do wonder if you might need to do it also for the !enable
> case. That is, suppose we've had the alarm set for 01:02:15. The alarm
> fires, we do stuff, and then we want to turn it off. So this gets called
> with some 00:00:00 value in alarm_tm and enable==0. Then when we start
> writing the new register values, as soon as REG_SCA0 has been written
> to, the alarm condition for 01:02:xx is automatically satisfied.
>
> If you unconditionally write a "four days in the future, with alarm bit
> set" value to DWA0, that should prevent this and the DWA0 does get its
> !enable value set via the bulk_write.

Good idea. I will remove the condition for the DWA0 trick.

>> +	/* write ALARM registers */
>> +	ret = regmap_bulk_write(regmap, ISL12022_REG_SCA0,
>> +				&regs, sizeof(regs));
>
> Nit: Fits in one line (I think), and you probably want to use the
> ISL12022_ALARM_SECTION name here, even if they're of course the same.

Using ISL12022_ALARM_SECTION makes the line 85 columns. I must admit I
feel a bit uneasy about going over the 80 columns, as I have no idea
when to wrap the lines then...

>> +	if (ret) {
>> +		dev_err(dev, "%s: writing ALARM registers failed\n", __func__);
>> +		return ret;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static irqreturn_t isl12022_rtc_interrupt(int irq, void *data)
>> +{
>> +	struct isl12022 *isl12022 = data;
>> +	struct rtc_device *rtc = isl12022->rtc;
>> +	struct device *dev = &rtc->dev;
>> +	struct regmap *regmap = isl12022->regmap;
>> +	u32 val = 0;
>> +	unsigned long events = 0;
>> +	int ret;
>> +
>> +	ret = regmap_read(regmap, ISL12022_REG_SR, &val);
>> +	if (ret) {
>> +		dev_err(dev, "%s: reading SR failed\n", __func__);
>> +		return IRQ_HANDLED;
>> +	}
>> +
>> +	if (val & ISL12022_SR_ALM)
>> +		events |= RTC_IRQF | RTC_AF;
>> +
>> +	if (events & RTC_AF)
>> +		dev_dbg(dev, "alarm!\n");
>> +
>> +	if (!events)
>> +		return IRQ_NONE;
>> +
>> +	rtc_update_irq(rtc, 1, events);
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static int isl12022_rtc_alarm_irq_enable(struct device *dev,
>> +					 unsigned int enabled)
>> +{
>> +	struct isl12022 *isl12022 = dev_get_drvdata(dev);
>> +
>> +	if (!isl12022->irq_enabled == !enabled)
>> +		return 0;
>> +
>> +	if (enabled)
>> +		enable_irq(isl12022->irq);
>> +	else
>> +		disable_irq(isl12022->irq);
>> +
>> +	isl12022->irq_enabled = !!enabled;
>> +
>
> I see why you do the ! and !! dances to canonicalize boolean values for
> comparison, but it's not very pretty. But ->alarm_irq_enable has the
> signature it has (that should probably get changed), so to be safe I
> guess you do need them. That said, I don't think it's unreasonable to
> assume that ->alarm_irq_enable is only ever invoked with the values 0
> and 1 for the enabled argument, and e.g. rtc-cpcap.c gets away with that
> assumption.

The handling in rtc-cpcap.c looks a bit strange IMHO. The comparison is
without using !, and then the assignment is done with !!. I think we
should either rely on enabled always being either 0 or 1, or handle the
cases where it might be something else.

I prefer to play it safe for now.

But if I explicitly do this first

    /* Make sure enabled is 0 or 1 */
    enabled = !!enabled;

Then we can leave out the ! and !! below. The code should be more
readable, and it will be much clearer for anyone that later on will want
to get rid of this.

>> +	return 0;
>> +}
>> +
>> +static int isl12022_setup_irq(struct isl12022 *isl12022, int irq)
>> +{
>> +	struct device *dev = &isl12022->i2c->dev;
>
> I was wondering why you needed to stash the i2c_client, but I see it
> here. The other initialization helpers (_set_trip_levels and
> _hwmon_register) are passed &client->dev so they have this dev directly,
> and they then get the regmap (or, with patch 1, the struct isl12022)
> from that with dev_get_drvdata(). For consistency I think you should do
> the same, and then you can drop the i2c field in struct isl12022.

Good idea. I had been thinking about something like this, but got away
from it again. I will change it in v2.

>> +	struct regmap *regmap = isl12022->regmap;
>> +	unsigned int reg_mask, reg_val;
>> +	u8 buf[ISL12022_ALARM_SECTION_LEN] = { 0, };
>> +	int ret;
>> +
>> +	/* Clear and disable all alarm registers */
>> +	ret = regmap_bulk_write(regmap, ISL12022_ALARM_SECTION,
>> +				buf, sizeof(buf));
>> +	if (ret)
>> +		return ret;
>> +
>> +	/* Enable automatic reset of ALM bit, enable single event interrupt
>> +	 * mode, and disable IRQ/fOUT pin during battery-backup mode.
>> +	 */
>
> Network-style.

Got it.

>
>> +	reg_mask = ISL12022_INT_ARST | ISL12022_INT_IM
>> +		| ISL12022_INT_FOBATB | ISL12022_INT_FO_MASK;
>> +	reg_val = ISL12022_INT_ARST | ISL12022_INT_FOBATB | ISL12022_INT_FO_OFF;
>> +	ret = regmap_write_bits(regmap, ISL12022_REG_INT,
>> +				reg_mask, reg_val);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = devm_request_threaded_irq(dev, irq, NULL,
>> +					isl12022_rtc_interrupt,
>> +					IRQF_SHARED | IRQF_ONESHOT,
>> +					isl12022_driver.driver.name,
>> +					isl12022);
>> +	if (ret) {
>> +		dev_err(dev, "Unable to request irq %d\n", irq);
>> +		return ret;
>
> This should probably be "return dev_err_probe(...);" - the irq could in
> theory be routed to some gpio expander which is not yet probed, so we
> could get -EPROBE_DEFER. And regardless, dev_err_probe has the advantage
> of printing what the err code actually is.

I will change this both this and the other dev_err() in _probe() to
dev_err_probe().

/Esben

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