sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 333 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-da9052.c b/drivers/rtc/rtc-da9052.c
new file mode 100644
index 000000000..9ca99bd35
--- /dev/null
+++ b/drivers/rtc/rtc-da9052.c
@@ -0,0 +1,333 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Real time clock driver for DA9052
+ *
+ * Copyright(c) 2012 Dialog Semiconductor Ltd.
+ *
+ * Author: Dajun Dajun Chen <dajun.chen@diasemi.com>
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+
+#include <linux/mfd/da9052/da9052.h>
+#include <linux/mfd/da9052/reg.h>
+
+#define rtc_err(rtc, fmt, ...) \
+		dev_err(rtc->da9052->dev, "%s: " fmt, __func__, ##__VA_ARGS__)
+
+#define DA9052_GET_TIME_RETRIES 5
+
+struct da9052_rtc {
+	struct rtc_device *rtc;
+	struct da9052 *da9052;
+};
+
+static int da9052_rtc_enable_alarm(struct da9052_rtc *rtc, bool enable)
+{
+	int ret;
+	if (enable) {
+		ret = da9052_reg_update(rtc->da9052, DA9052_ALARM_Y_REG,
+				DA9052_ALARM_Y_ALARM_ON|DA9052_ALARM_Y_TICK_ON,
+				DA9052_ALARM_Y_ALARM_ON);
+		if (ret != 0)
+			rtc_err(rtc, "Failed to enable ALM: %d\n", ret);
+	} else {
+		ret = da9052_reg_update(rtc->da9052, DA9052_ALARM_Y_REG,
+			DA9052_ALARM_Y_ALARM_ON|DA9052_ALARM_Y_TICK_ON, 0);
+		if (ret != 0)
+			rtc_err(rtc, "Write error: %d\n", ret);
+	}
+	return ret;
+}
+
+static irqreturn_t da9052_rtc_irq(int irq, void *data)
+{
+	struct da9052_rtc *rtc = data;
+
+	rtc_update_irq(rtc->rtc, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static int da9052_read_alarm(struct da9052_rtc *rtc, struct rtc_time *rtc_tm)
+{
+	int ret;
+	uint8_t v[2][5];
+	int idx = 1;
+	int timeout = DA9052_GET_TIME_RETRIES;
+
+	ret = da9052_group_read(rtc->da9052, DA9052_ALARM_MI_REG, 5, &v[0][0]);
+	if (ret) {
+		rtc_err(rtc, "Failed to group read ALM: %d\n", ret);
+		return ret;
+	}
+
+	do {
+		ret = da9052_group_read(rtc->da9052,
+					DA9052_ALARM_MI_REG, 5, &v[idx][0]);
+		if (ret) {
+			rtc_err(rtc, "Failed to group read ALM: %d\n", ret);
+			return ret;
+		}
+
+		if (memcmp(&v[0][0], &v[1][0], 5) == 0) {
+			rtc_tm->tm_year = (v[0][4] & DA9052_RTC_YEAR) + 100;
+			rtc_tm->tm_mon  = (v[0][3] & DA9052_RTC_MONTH) - 1;
+			rtc_tm->tm_mday = v[0][2] & DA9052_RTC_DAY;
+			rtc_tm->tm_hour = v[0][1] & DA9052_RTC_HOUR;
+			rtc_tm->tm_min  = v[0][0] & DA9052_RTC_MIN;
+			rtc_tm->tm_sec = 0;
+
+			ret = rtc_valid_tm(rtc_tm);
+			return ret;
+		}
+
+		idx = (1-idx);
+		msleep(20);
+
+	} while (timeout--);
+
+	rtc_err(rtc, "Timed out reading alarm time\n");
+
+	return -EIO;
+}
+
+static int da9052_set_alarm(struct da9052_rtc *rtc, struct rtc_time *rtc_tm)
+{
+	struct da9052 *da9052 = rtc->da9052;
+	unsigned long alm_time;
+	int ret;
+	uint8_t v[3];
+
+	alm_time = rtc_tm_to_time64(rtc_tm);
+
+	if (rtc_tm->tm_sec > 0) {
+		alm_time += 60 - rtc_tm->tm_sec;
+		rtc_time64_to_tm(alm_time, rtc_tm);
+	}
+	BUG_ON(rtc_tm->tm_sec); /* it will cause repeated irqs if not zero */
+
+	rtc_tm->tm_year -= 100;
+	rtc_tm->tm_mon += 1;
+
+	ret = da9052_reg_update(da9052, DA9052_ALARM_MI_REG,
+				DA9052_RTC_MIN, rtc_tm->tm_min);
+	if (ret != 0) {
+		rtc_err(rtc, "Failed to write ALRM MIN: %d\n", ret);
+		return ret;
+	}
+
+	v[0] = rtc_tm->tm_hour;
+	v[1] = rtc_tm->tm_mday;
+	v[2] = rtc_tm->tm_mon;
+
+	ret = da9052_group_write(da9052, DA9052_ALARM_H_REG, 3, v);
+	if (ret < 0)
+		return ret;
+
+	ret = da9052_reg_update(da9052, DA9052_ALARM_Y_REG,
+				DA9052_RTC_YEAR, rtc_tm->tm_year);
+	if (ret != 0)
+		rtc_err(rtc, "Failed to write ALRM YEAR: %d\n", ret);
+
+	return ret;
+}
+
+static int da9052_rtc_get_alarm_status(struct da9052_rtc *rtc)
+{
+	int ret;
+
+	ret = da9052_reg_read(rtc->da9052, DA9052_ALARM_Y_REG);
+	if (ret < 0) {
+		rtc_err(rtc, "Failed to read ALM: %d\n", ret);
+		return ret;
+	}
+
+	return !!(ret&DA9052_ALARM_Y_ALARM_ON);
+}
+
+static int da9052_rtc_read_time(struct device *dev, struct rtc_time *rtc_tm)
+{
+	struct da9052_rtc *rtc = dev_get_drvdata(dev);
+	int ret;
+	uint8_t v[2][6];
+	int idx = 1;
+	int timeout = DA9052_GET_TIME_RETRIES;
+
+	ret = da9052_group_read(rtc->da9052, DA9052_COUNT_S_REG, 6, &v[0][0]);
+	if (ret) {
+		rtc_err(rtc, "Failed to read RTC time : %d\n", ret);
+		return ret;
+	}
+
+	do {
+		ret = da9052_group_read(rtc->da9052,
+					DA9052_COUNT_S_REG, 6, &v[idx][0]);
+		if (ret) {
+			rtc_err(rtc, "Failed to read RTC time : %d\n", ret);
+			return ret;
+		}
+
+		if (memcmp(&v[0][0], &v[1][0], 6) == 0) {
+			rtc_tm->tm_year = (v[0][5] & DA9052_RTC_YEAR) + 100;
+			rtc_tm->tm_mon  = (v[0][4] & DA9052_RTC_MONTH) - 1;
+			rtc_tm->tm_mday = v[0][3] & DA9052_RTC_DAY;
+			rtc_tm->tm_hour = v[0][2] & DA9052_RTC_HOUR;
+			rtc_tm->tm_min  = v[0][1] & DA9052_RTC_MIN;
+			rtc_tm->tm_sec  = v[0][0] & DA9052_RTC_SEC;
+
+			return 0;
+		}
+
+		idx = (1-idx);
+		msleep(20);
+
+	} while (timeout--);
+
+	rtc_err(rtc, "Timed out reading time\n");
+
+	return -EIO;
+}
+
+static int da9052_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct da9052_rtc *rtc;
+	uint8_t v[6];
+	int ret;
+
+	/* DA9052 only has 6 bits for year - to represent 2000-2063 */
+	if ((tm->tm_year < 100) || (tm->tm_year > 163))
+		return -EINVAL;
+
+	rtc = dev_get_drvdata(dev);
+
+	v[0] = tm->tm_sec;
+	v[1] = tm->tm_min;
+	v[2] = tm->tm_hour;
+	v[3] = tm->tm_mday;
+	v[4] = tm->tm_mon + 1;
+	v[5] = tm->tm_year - 100;
+
+	ret = da9052_group_write(rtc->da9052, DA9052_COUNT_S_REG, 6, v);
+	if (ret < 0)
+		rtc_err(rtc, "failed to set RTC time: %d\n", ret);
+	return ret;
+}
+
+static int da9052_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	int ret;
+	struct rtc_time *tm = &alrm->time;
+	struct da9052_rtc *rtc = dev_get_drvdata(dev);
+
+	ret = da9052_read_alarm(rtc, tm);
+	if (ret < 0) {
+		rtc_err(rtc, "failed to read RTC alarm: %d\n", ret);
+		return ret;
+	}
+
+	alrm->enabled = da9052_rtc_get_alarm_status(rtc);
+	return 0;
+}
+
+static int da9052_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	int ret;
+	struct rtc_time *tm = &alrm->time;
+	struct da9052_rtc *rtc = dev_get_drvdata(dev);
+
+	/* DA9052 only has 6 bits for year - to represent 2000-2063 */
+	if ((tm->tm_year < 100) || (tm->tm_year > 163))
+		return -EINVAL;
+
+	ret = da9052_rtc_enable_alarm(rtc, 0);
+	if (ret < 0)
+		return ret;
+
+	ret = da9052_set_alarm(rtc, tm);
+	if (ret < 0)
+		return ret;
+
+	ret = da9052_rtc_enable_alarm(rtc, 1);
+	return ret;
+}
+
+static int da9052_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct da9052_rtc *rtc = dev_get_drvdata(dev);
+
+	return da9052_rtc_enable_alarm(rtc, enabled);
+}
+
+static const struct rtc_class_ops da9052_rtc_ops = {
+	.read_time	= da9052_rtc_read_time,
+	.set_time	= da9052_rtc_set_time,
+	.read_alarm	= da9052_rtc_read_alarm,
+	.set_alarm	= da9052_rtc_set_alarm,
+	.alarm_irq_enable = da9052_rtc_alarm_irq_enable,
+};
+
+static int da9052_rtc_probe(struct platform_device *pdev)
+{
+	struct da9052_rtc *rtc;
+	int ret;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(struct da9052_rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	rtc->da9052 = dev_get_drvdata(pdev->dev.parent);
+	platform_set_drvdata(pdev, rtc);
+
+	ret = da9052_reg_write(rtc->da9052, DA9052_BBAT_CONT_REG, 0xFE);
+	if (ret < 0) {
+		rtc_err(rtc,
+			"Failed to setup RTC battery charging: %d\n", ret);
+		return ret;
+	}
+
+	ret = da9052_reg_update(rtc->da9052, DA9052_ALARM_Y_REG,
+				DA9052_ALARM_Y_TICK_ON, 0);
+	if (ret != 0)
+		rtc_err(rtc, "Failed to disable TICKS: %d\n", ret);
+
+	device_init_wakeup(&pdev->dev, true);
+	rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc->rtc))
+		return PTR_ERR(rtc->rtc);
+
+	rtc->rtc->ops = &da9052_rtc_ops;
+	rtc->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	rtc->rtc->range_max = RTC_TIMESTAMP_END_2063;
+
+	ret = devm_rtc_register_device(rtc->rtc);
+	if (ret)
+		return ret;
+
+	ret = da9052_request_irq(rtc->da9052, DA9052_IRQ_ALARM, "ALM",
+				da9052_rtc_irq, rtc);
+	if (ret != 0) {
+		rtc_err(rtc, "irq registration failed: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct platform_driver da9052_rtc_driver = {
+	.probe	= da9052_rtc_probe,
+	.driver = {
+		.name	= "da9052-rtc",
+	},
+};
+
+module_platform_driver(da9052_rtc_driver);
+
+MODULE_AUTHOR("Anthony Olech <Anthony.Olech@diasemi.com>");
+MODULE_DESCRIPTION("RTC driver for Dialog DA9052 PMIC");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:da9052-rtc");