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Subject[PATCH v2 2/2] misc: Add power-efuse driver
Date
This driver provides a sysfs interface to access the on/off state and
error flags of a regulator supplying a power output controlled by the
system.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
---
.../ABI/testing/sysfs-driver-power-efuse | 32 +++
MAINTAINERS | 5 +
drivers/misc/Kconfig | 15 ++
drivers/misc/Makefile | 1 +
drivers/misc/power-efuse.c | 212 ++++++++++++++++++
5 files changed, 265 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-driver-power-efuse
create mode 100644 drivers/misc/power-efuse.c

diff --git a/Documentation/ABI/testing/sysfs-driver-power-efuse b/Documentation/ABI/testing/sysfs-driver-power-efuse
new file mode 100644
index 000000000000..ff9bb53e012a
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-power-efuse
@@ -0,0 +1,32 @@
+What: /sys/bus/platform/drivers/power-efuse/\*/operstate
+Date: February 2022
+KernelVersion: 5.18
+Contact: Zev Weiss <zev@bewilderbeest.net
+Description: The operating state of the efuse as either "on" or "off"; either
+ value can be written to set the operating state.
+Users: OpenBMC <openbmc@lists.ozlabs.org>
+
+What: /sys/bus/platform/drivers/power-efuse/\*/fail
+Date: February 2022
+KernelVersion: 5.18
+Contact: Zev Weiss <zev@bewilderbeest.net
+Description: 0 if the efuse is operating normally, or 1 if it has tripped
+ (operating state set to "on" but the hardware has shut off the
+ output due to a fault).
+Users: OpenBMC <openbmc@lists.ozlabs.org>
+
+What: /sys/bus/platform/drivers/power-efuse/\*/{under_voltage,over_current,regulation_out,over_temp}
+Date: February 2022
+KernelVersion: 5.18
+Contact: Zev Weiss <zev@bewilderbeest.net
+Description: 1 if the underlying regulator reports a fault of the type
+ indicated by the name of the file, 0 otherwise.
+Users: OpenBMC <openbmc@lists.ozlabs.org>
+
+What: /sys/bus/platform/drivers/power-efuse/\*/{under_voltage,over_current,over_voltage,over_temp}_warn
+Date: February 2022
+KernelVersion: 5.18
+Contact: Zev Weiss <zev@bewilderbeest.net
+Description: 1 if the underlying regulator reports a warning of the type
+ indicated by the name of the file, 0 otherwise.
+Users: OpenBMC <openbmc@lists.ozlabs.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 05fd080b82f3..6490b09b43d4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7058,6 +7058,11 @@ S: Orphan
W: http://aeschi.ch.eu.org/efs/
F: fs/efs/

+POWER EFUSE DRIVER
+M: Zev Weiss <zev@bewilderbeest.net>
+S: Maintained
+F: drivers/misc/power-efuse.c
+
EHEA (IBM pSeries eHEA 10Gb ethernet adapter) DRIVER
M: Douglas Miller <dougmill@linux.ibm.com>
L: netdev@vger.kernel.org
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 0f5a49fc7c9e..45fc3e8ad35d 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -470,6 +470,21 @@ config HISI_HIKEY_USB
switching between the dual-role USB-C port and the USB-A host ports
using only one USB controller.

+config POWER_EFUSE
+ tristate "Power efuse driver support"
+ depends on OF && REGULATOR
+ help
+ This driver supports a regulator device functioning as a
+ power efuse, with status bits and an on/off switch available
+ via sysfs.
+
+ A typical use for this would be for an efuse controlling a
+ generic power output for supplying power to devices external
+ to the system running this driver (such as in the management
+ controller of a "smart" PDU or similar), allowing the
+ operator to manually turn the output on and off, check if
+ the efuse has tripped due to overload, etc.
+
source "drivers/misc/c2port/Kconfig"
source "drivers/misc/eeprom/Kconfig"
source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index a086197af544..7bd784b89ef8 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -59,3 +59,4 @@ obj-$(CONFIG_UACCE) += uacce/
obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o
obj-$(CONFIG_HISI_HIKEY_USB) += hisi_hikey_usb.o
obj-$(CONFIG_HI6421V600_IRQ) += hi6421v600-irq.o
+obj-$(CONFIG_POWER_EFUSE) += power-efuse.o
diff --git a/drivers/misc/power-efuse.c b/drivers/misc/power-efuse.c
new file mode 100644
index 000000000000..e9d2feb668f2
--- /dev/null
+++ b/drivers/misc/power-efuse.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This module provides a thin wrapper around a regulator device that exposes
+ * status bits and on/off state via sysfs.
+ *
+ * Copyright (C) 2022 Zev Weiss <zev@bewilderbeest.net>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+
+struct efuse {
+ struct regulator *reg;
+ struct {
+ unsigned int cache;
+ unsigned long ttl;
+ unsigned long fetch_time;
+ struct mutex lock;
+ } error_flags;
+};
+
+/* Ensure that the next error_flags access fetches them from the device */
+static void efuse_invalidate_error_flags(struct efuse *efuse)
+{
+ mutex_lock(&efuse->error_flags.lock);
+ efuse->error_flags.fetch_time = 0;
+ mutex_unlock(&efuse->error_flags.lock);
+}
+
+static ssize_t efuse_show_operstate(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct efuse *efuse = dev_get_drvdata(dev);
+ int status = regulator_is_enabled(efuse->reg);
+
+ if (status < 0)
+ return status;
+
+ return sysfs_emit(buf, "%s\n", status ? "on" : "off");
+}
+
+static ssize_t efuse_set_operstate(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int status, wantstate;
+ struct efuse *efuse = dev_get_drvdata(dev);
+ struct regulator *reg = efuse->reg;
+
+ if (sysfs_streq(buf, "on"))
+ wantstate = 1;
+ else if (sysfs_streq(buf, "off"))
+ wantstate = 0;
+ else
+ return -EINVAL;
+
+ status = regulator_is_enabled(reg);
+
+ /*
+ * We need to ensure our enable/disable calls don't get imbalanced, so
+ * bail if we can't determine the current state.
+ */
+ if (status < 0)
+ return status;
+
+ /* Return early if we're already in the desired state */
+ if (!!status == wantstate)
+ return count;
+
+ if (wantstate)
+ status = regulator_enable(reg);
+ else
+ status = regulator_disable(reg);
+
+ /*
+ * Toggling operstate can reset latched status flags, so invalidate
+ * the cached value.
+ */
+ efuse_invalidate_error_flags(efuse);
+
+ if (!status && regulator_is_enabled(reg) != wantstate) {
+ /*
+ * We could do
+ *
+ * if (!wantstate)
+ * regulator_force_disable(reg);
+ *
+ * here, but it's likely to leave it such that it can't then
+ * be re-enabled, so we'll just report the error and leave it
+ * as it is (and hopefully as long as our enable/disable calls
+ * remain balanced and nobody registers another consumer for
+ * the same supply we won't end up in this situation anyway).
+ */
+ dev_err(dev, "regulator_%sable() didn't take effect\n", wantstate ? "en" : "dis");
+ status = -EIO;
+ }
+
+ return status ? : count;
+}
+
+static int efuse_update_error_flags(struct efuse *efuse)
+{
+ int status = 0;
+ unsigned long cache_expiry;
+
+ mutex_lock(&efuse->error_flags.lock);
+
+ cache_expiry = efuse->error_flags.fetch_time + efuse->error_flags.ttl;
+
+ if (!efuse->error_flags.ttl || !efuse->error_flags.fetch_time ||
+ time_after(jiffies, cache_expiry)) {
+ status = regulator_get_error_flags(efuse->reg, &efuse->error_flags.cache);
+ if (!status)
+ efuse->error_flags.fetch_time = jiffies;
+ }
+
+ mutex_unlock(&efuse->error_flags.lock);
+
+ return status;
+}
+
+static DEVICE_ATTR(operstate, 0644, efuse_show_operstate, efuse_set_operstate);
+
+#define EFUSE_ERROR_ATTR(name, bit) \
+ static ssize_t efuse_show_##name(struct device *dev, struct device_attribute *attr, \
+ char *buf) \
+ { \
+ struct efuse *efuse = dev_get_drvdata(dev); \
+ int status = efuse_update_error_flags(efuse); \
+ if (status) \
+ return status; \
+ return sysfs_emit(buf, "%d\n", !!(efuse->error_flags.cache & bit)); \
+ } \
+ static DEVICE_ATTR(name, 0444, efuse_show_##name, NULL)
+
+EFUSE_ERROR_ATTR(under_voltage, REGULATOR_ERROR_UNDER_VOLTAGE);
+EFUSE_ERROR_ATTR(over_current, REGULATOR_ERROR_OVER_CURRENT);
+EFUSE_ERROR_ATTR(regulation_out, REGULATOR_ERROR_REGULATION_OUT);
+EFUSE_ERROR_ATTR(fail, REGULATOR_ERROR_FAIL);
+EFUSE_ERROR_ATTR(over_temp, REGULATOR_ERROR_OVER_TEMP);
+EFUSE_ERROR_ATTR(under_voltage_warn, REGULATOR_ERROR_UNDER_VOLTAGE_WARN);
+EFUSE_ERROR_ATTR(over_current_warn, REGULATOR_ERROR_OVER_CURRENT_WARN);
+EFUSE_ERROR_ATTR(over_voltage_warn, REGULATOR_ERROR_OVER_VOLTAGE_WARN);
+EFUSE_ERROR_ATTR(over_temp_warn, REGULATOR_ERROR_OVER_TEMP_WARN);
+
+static struct attribute *efuse_attrs[] = {
+ &dev_attr_operstate.attr,
+ &dev_attr_under_voltage.attr,
+ &dev_attr_over_current.attr,
+ &dev_attr_regulation_out.attr,
+ &dev_attr_fail.attr,
+ &dev_attr_over_temp.attr,
+ &dev_attr_under_voltage_warn.attr,
+ &dev_attr_over_current_warn.attr,
+ &dev_attr_over_voltage_warn.attr,
+ &dev_attr_over_temp_warn.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(efuse);
+
+static int efuse_probe(struct platform_device *pdev)
+{
+ int status;
+ struct regulator *reg;
+ struct efuse *efuse;
+ u32 cache_ttl_ms;
+
+ reg = devm_regulator_get(&pdev->dev, "vout");
+ if (IS_ERR(reg))
+ return PTR_ERR(reg);
+
+ status = regulator_enable(reg);
+ if (status) {
+ dev_err(&pdev->dev, "failed to enable regulator\n");
+ return status;
+ }
+
+ efuse = devm_kzalloc(&pdev->dev, sizeof(*efuse), GFP_KERNEL);
+ if (!efuse)
+ return -ENOMEM;
+
+ efuse->reg = reg;
+ mutex_init(&efuse->error_flags.lock);
+
+ if (!of_property_read_u32(pdev->dev.of_node, "error-flags-cache-ttl-ms", &cache_ttl_ms))
+ efuse->error_flags.ttl = msecs_to_jiffies(cache_ttl_ms);
+
+ platform_set_drvdata(pdev, efuse);
+
+ return 0;
+}
+
+static const struct of_device_id efuse_of_match_table[] = {
+ { .compatible = "power-efuse" },
+ { },
+};
+
+static struct platform_driver efuse_driver = {
+ .driver = {
+ .name = "power-efuse",
+ .of_match_table = efuse_of_match_table,
+ .dev_groups = efuse_groups,
+ },
+ .probe = efuse_probe,
+};
+module_platform_driver(efuse_driver);
+
+MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Power efuse driver");
--
2.35.1
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