Re: [PATCH v2] mlxbf-bootctl: Support sysfs entries for RTC battery status

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Thu, 16 Jan 2025, Xiangrong Li wrote:

> 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@nvidia.com>
> Reviewed-by: David Thompson <davthompson@nvidia.com>
> ---
>  .../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

The ship for 6.14 has sailed so this should be changed to 6.15, and please 
also estimate the date of the release which is not same as date of 
submission of the patch.

When you have fixed those, feel free to add:

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

-- 
 i.

> +Contact:	"Xiangrong Li <xiangrongl@nvidia.com>"
> +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
>