ACPI: TAD: Add low-level support for real time capability

Add low-level support for the (optional) real time capability of the
ACPI Time and Alarm Device (TAD) to the ACPI TAD driver.

This allows the real time to be acquired or set via sysfs with the
help of the _GRT and _SRT methods of the TAD, respectively.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/acpi/acpi_tad.c

@@ -52,6 +52,201 @@ struct acpi_tad_driver_data {
 	u32 capabilities;
 };
 
+struct acpi_tad_rt {
+	u16 year;  /* 1900 - 9999 */
+	u8 month;  /* 1 - 12 */
+	u8 day;    /* 1 - 31 */
+	u8 hour;   /* 0 - 23 */
+	u8 minute; /* 0 - 59 */
+	u8 second; /* 0 - 59 */
+	u8 valid;  /* 0 (failed) or 1 (success) for reads, 0 for writes */
+	u16 msec;  /* 1 - 1000 */
+	s16 tz;    /* -1440 to 1440 or 2047 (unspecified) */
+	u8 daylight;
+	u8 padding[3]; /* must be 0 */
+} __packed;
+
+static int acpi_tad_set_real_time(struct device *dev, struct acpi_tad_rt *rt)
+{
+	acpi_handle handle = ACPI_HANDLE(dev);
+	union acpi_object args[] = {
+		{ .type = ACPI_TYPE_BUFFER, },
+	};
+	struct acpi_object_list arg_list = {
+		.pointer = args,
+		.count = ARRAY_SIZE(args),
+	};
+	unsigned long long retval;
+	acpi_status status;
+
+	if (rt->year < 1900 || rt->year > 9999 ||
+	    rt->month < 1 || rt->month > 12 ||
+	    rt->hour > 23 || rt->minute > 59 || rt->second > 59 ||
+	    rt->tz < -1440 || (rt->tz > 1440 && rt->tz != 2047) ||
+	    rt->daylight > 3)
+		return -ERANGE;
+
+	args[0].buffer.pointer = (u8 *)rt;
+	args[0].buffer.length = sizeof(*rt);
+
+	pm_runtime_get_sync(dev);
+
+	status = acpi_evaluate_integer(handle, "_SRT", &arg_list, &retval);
+
+	pm_runtime_put_sync(dev);
+
+	if (ACPI_FAILURE(status) || retval)
+		return -EIO;
+
+	return 0;
+}
+
+static int acpi_tad_get_real_time(struct device *dev, struct acpi_tad_rt *rt)
+{
+	acpi_handle handle = ACPI_HANDLE(dev);
+	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER };
+	union acpi_object *out_obj;
+	struct acpi_tad_rt *data;
+	acpi_status status;
+	int ret = -EIO;
+
+	pm_runtime_get_sync(dev);
+
+	status = acpi_evaluate_object(handle, "_GRT", NULL, &output);
+
+	pm_runtime_put_sync(dev);
+
+	if (ACPI_FAILURE(status))
+		goto out_free;
+
+	out_obj = output.pointer;
+	if (out_obj->type != ACPI_TYPE_BUFFER)
+		goto out_free;
+
+	if (out_obj->buffer.length != sizeof(*rt))
+		goto out_free;
+
+	data = (struct acpi_tad_rt *)(out_obj->buffer.pointer);
+	if (!data->valid)
+		goto out_free;
+
+	memcpy(rt, data, sizeof(*rt));
+	ret = 0;
+
+out_free:
+	ACPI_FREE(output.pointer);
+	return ret;
+}
+
+static char *acpi_tad_rt_next_field(char *s, int *val)
+{
+	char *p;
+
+	p = strchr(s, ':');
+	if (!p)
+		return NULL;
+
+	*p = '\0';
+	if (kstrtoint(s, 10, val))
+		return NULL;
+
+	return p + 1;
+}
+
+static ssize_t time_store(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct acpi_tad_rt rt;
+	char *str, *s;
+	int val, ret = -ENODATA;
+
+	str = kmemdup_nul(buf, count, GFP_KERNEL);
+	if (!str)
+		return -ENOMEM;
+
+	s = acpi_tad_rt_next_field(str, &val);
+	if (!s)
+		goto out_free;
+
+	rt.year = val;
+
+	s = acpi_tad_rt_next_field(s, &val);
+	if (!s)
+		goto out_free;
+
+	rt.month = val;
+
+	s = acpi_tad_rt_next_field(s, &val);
+	if (!s)
+		goto out_free;
+
+	rt.day = val;
+
+	s = acpi_tad_rt_next_field(s, &val);
+	if (!s)
+		goto out_free;
+
+	rt.hour = val;
+
+	s = acpi_tad_rt_next_field(s, &val);
+	if (!s)
+		goto out_free;
+
+	rt.minute = val;
+
+	s = acpi_tad_rt_next_field(s, &val);
+	if (!s)
+		goto out_free;
+
+	rt.second = val;
+
+	s = acpi_tad_rt_next_field(s, &val);
+	if (!s)
+		goto out_free;
+
+	rt.tz = val;
+
+	if (kstrtoint(s, 10, &val))
+		goto out_free;
+
+	rt.daylight = val;
+
+	rt.valid = 0;
+	rt.msec = 0;
+	memset(rt.padding, 0, 3);
+
+	ret = acpi_tad_set_real_time(dev, &rt);
+
+out_free:
+	kfree(str);
+	return ret ? ret : count;
+}
+
+static ssize_t time_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct acpi_tad_rt rt;
+	int ret;
+
+	ret = acpi_tad_get_real_time(dev, &rt);
+	if (ret)
+		return ret;
+
+	return sprintf(buf, "%u:%u:%u:%u:%u:%u:%d:%u\n",
+		       rt.year, rt.month, rt.day, rt.hour, rt.minute, rt.second,
+		       rt.tz, rt.daylight);
+}
+
+static DEVICE_ATTR(time, S_IRUSR | S_IWUSR, time_show, time_store);
+
+static struct attribute *acpi_tad_time_attrs[] = {
+	&dev_attr_time.attr,
+	NULL,
+};
+static const struct attribute_group acpi_tad_time_attr_group = {
+	.attrs	= acpi_tad_time_attrs,
+};
+
 static int acpi_tad_wake_set(struct device *dev, char *method, u32 timer_id,
 			     u32 value)
 {
@@ -448,6 +643,12 @@ static int acpi_tad_probe(struct platform_device *pdev)
 			goto fail;
 	}
 
+	if (caps & ACPI_TAD_RT) {
+		ret = sysfs_create_group(&dev->kobj, &acpi_tad_time_attr_group);
+		if (ret)
+			goto fail;
+	}
+
 	return 0;
 
 fail: