This patch extends the mlxbf-bootctl driver's sysfs entries
to support read access for the board's RTC battery status.
A successful read from this attribute returns the status of
the board's RTC battery. The RTC battery status register is
also cleared upon successful read operation.
Signed-off-by: Xiangrong Li <xiangrongl@xxxxxxxxxx>
Reviewed-by: David Thompson <davthompson@xxxxxxxxxx>
---
.../testing/sysfs-platform-mellanox-bootctl | 10 ++++++++++
drivers/platform/mellanox/mlxbf-bootctl.c | 20 +++++++++++++++++++
drivers/platform/mellanox/mlxbf-bootctl.h | 5 +++++
3 files changed, 35 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl b/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl
index 65ed3865da62..65614fba62b8 100644
--- a/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl
+++ b/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl
@@ -150,3 +150,13 @@ Description:
The "mfg_lock" sysfs attribute is write-only.
A successful write to this attribute will latch the
board-level attributes into EEPROM, making them read-only.
+
+What: /sys/bus/platform/devices/MLNXBF04:00/rtc_battery
+Date: January 2025
+KernelVersion: 6.14
+Contact: "Xiangrong Li <xiangrongl@xxxxxxxxxx>"
+Description:
+ The "rtc_battery" sysfs attribute is read-only.
+ A successful read from this attribute returns the status of
+ the board's RTC battery. The RTC battery status register is
+ also cleared upon successful read operation.
diff --git a/drivers/platform/mellanox/mlxbf-bootctl.c b/drivers/platform/mellanox/mlxbf-bootctl.c
index c5b36837e694..bc31061f779c 100644
--- a/drivers/platform/mellanox/mlxbf-bootctl.c
+++ b/drivers/platform/mellanox/mlxbf-bootctl.c
@@ -91,6 +91,7 @@ static const char * const mlxbf_rsh_log_level[] = {
static DEFINE_MUTEX(icm_ops_lock);
static DEFINE_MUTEX(os_up_lock);
static DEFINE_MUTEX(mfg_ops_lock);
+static DEFINE_MUTEX(rtc_ops_lock);
/*
* Objects are stored within the MFG partition per type.
@@ -489,6 +490,23 @@ static ssize_t large_icm_store(struct device *dev,
return res.a0 ? -EPERM : count;
}
+static ssize_t rtc_battery_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct arm_smccc_res res;
+
+ mutex_lock(&rtc_ops_lock);
+ arm_smccc_smc(MLNX_HANDLE_GET_RTC_LOW_BATT, 0, 0, 0, 0,
+ 0, 0, 0, &res);
+ mutex_unlock(&rtc_ops_lock);
+
+ if (res.a0)
+ return -EPERM;
+
+ return sysfs_emit(buf, "0x%lx\n", res.a1);
+}
+
static ssize_t os_up_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
@@ -906,6 +924,7 @@ static DEVICE_ATTR_RW(sn);
static DEVICE_ATTR_RW(uuid);
static DEVICE_ATTR_RW(rev);
static DEVICE_ATTR_WO(mfg_lock);
+static DEVICE_ATTR_RO(rtc_battery);
static struct attribute *mlxbf_bootctl_attrs[] = {
&dev_attr_post_reset_wdog.attr,
@@ -925,6 +944,7 @@ static struct attribute *mlxbf_bootctl_attrs[] = {
&dev_attr_uuid.attr,
&dev_attr_rev.attr,
&dev_attr_mfg_lock.attr,
+ &dev_attr_rtc_battery.attr,
NULL
};
diff --git a/drivers/platform/mellanox/mlxbf-bootctl.h b/drivers/platform/mellanox/mlxbf-bootctl.h
index 1299750a8661..90bbbdc65879 100644
--- a/drivers/platform/mellanox/mlxbf-bootctl.h
+++ b/drivers/platform/mellanox/mlxbf-bootctl.h
@@ -103,6 +103,11 @@
*/
#define MLNX_HANDLE_OS_UP 0x82000014
+/*
+ * SMC function ID to get and clear the RTC low voltage bit
+ */
+#define MLNX_HANDLE_GET_RTC_LOW_BATT 0x82000023
+
/* SMC function IDs for SiP Service queries */
#define MLXBF_BOOTCTL_SIP_SVC_CALL_COUNT 0x8200ff00
#define MLXBF_BOOTCTL_SIP_SVC_UID 0x8200ff01
--
2.43.2
