[PATCH v2 0/3] Add support for runtime features

[PATCH v2 0/3] Add support for runtime features

[Ronak Jain]

Add support for runtime feature configuration by using the IOCTL
 calls. The user can enable or disable as well as can configure the
 runtime features. The support is added for the over temperature and
 external watchdog. The user can configure the over temperature limit
 and external watchdog timer interval at runtime by using PM_IOCTL
 calls.
 
Also, added support for sysfs interface for runtime feature
configuration for the over temperature and external watchdog features.

Changes in v2:
- Remove default footer from email
- Update commit message
- Resolved merged conflict

Ronak Jain (3):
  firmware: xilinx: Add support for runtime features
  firmware: zynqmp: Add sysfs entry for runtime features
  firmware: xilinx: Add sysfs support for feature config

 .../ABI/stable/sysfs-driver-firmware-zynqmp   | 84 ++++++++++++++++
 drivers/firmware/xilinx/zynqmp.c              | 98 +++++++++++++++++++
 include/linux/firmware/xlnx-zynqmp.h          | 25 +++++
 3 files changed, 207 insertions(+)

-- 
2.32.0.93.g670b81a

[PATCH v2 1/3] firmware: xilinx: Add support for runtime features

[Ronak Jain]

Add support for runtime features by using an IOCTL call. The features
 can be enabled or disabled on the firmware as well as the features
 can be configured at runtime by querying IOCTL_SET_FEATURE_CONFIG id.
 Similarly, the user can get the configured values of features by
 querying IOCTL_GET_FEATURE_CONFIG id.

Here, the support is added for the over temperature and external
 watchdog features only.

Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
---
Changes in v2:
- Resolved merged conflict
- Update commit message
---
 drivers/firmware/xilinx/zynqmp.c     | 27 +++++++++++++++++++++++++++
 include/linux/firmware/xlnx-zynqmp.h | 25 +++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/drivers/firmware/xilinx/zynqmp.c b/drivers/firmware/xilinx/zynqmp.c
index a3cadbaf3cba..875d13bc1a57 100644
--- a/drivers/firmware/xilinx/zynqmp.c
+++ b/drivers/firmware/xilinx/zynqmp.c
@@ -1066,6 +1066,33 @@ int zynqmp_pm_system_shutdown(const u32 type, const u32 subtype)
 				   0, 0, NULL);
 }
 
+/**
+ * zynqmp_pm_set_feature_config - PM call to request IOCTL for feature config
+ * @id:         The config ID of the feature to be configured
+ * @value:      The config value of the feature to be configured
+ *
+ * Return:      Returns 0 on success or error value on failure.
+ */
+int zynqmp_pm_set_feature_config(enum pm_feature_config_id id, u32 value)
+{
+	return zynqmp_pm_invoke_fn(PM_IOCTL, 0, IOCTL_SET_FEATURE_CONFIG,
+				   id, value, NULL);
+}
+
+/**
+ * zynqmp_pm_get_feature_config - PM call to get value of configured feature
+ * @id:         The config id of the feature to be queried
+ * @payload:    Returned value array
+ *
+ * Return:      Returns 0 on success or error value on failure.
+ */
+int zynqmp_pm_get_feature_config(enum pm_feature_config_id id,
+				 u32 *payload)
+{
+	return zynqmp_pm_invoke_fn(PM_IOCTL, 0, IOCTL_GET_FEATURE_CONFIG,
+				   id, 0, payload);
+}
+
 /**
  * struct zynqmp_pm_shutdown_scope - Struct for shutdown scope
  * @subtype:	Shutdown subtype
diff --git a/include/linux/firmware/xlnx-zynqmp.h b/include/linux/firmware/xlnx-zynqmp.h
index 56b426fe020c..25308b9ad109 100644
--- a/include/linux/firmware/xlnx-zynqmp.h
+++ b/include/linux/firmware/xlnx-zynqmp.h
@@ -123,6 +123,9 @@ enum pm_ioctl_id {
 	IOCTL_READ_PGGS = 15,
 	/* Set healthy bit value */
 	IOCTL_SET_BOOT_HEALTH_STATUS = 17,
+	/* Runtime feature configuration */
+	IOCTL_SET_FEATURE_CONFIG = 26,
+	IOCTL_GET_FEATURE_CONFIG = 27,
 };
 
 enum pm_query_id {
@@ -351,6 +354,14 @@ enum zynqmp_pm_shutdown_subtype {
 	ZYNQMP_PM_SHUTDOWN_SUBTYPE_SYSTEM = 2,
 };
 
+enum pm_feature_config_id {
+	PM_FEATURE_INVALID = 0,
+	PM_FEATURE_OVERTEMP_STATUS = 1,
+	PM_FEATURE_OVERTEMP_VALUE = 2,
+	PM_FEATURE_EXTWDT_STATUS = 3,
+	PM_FEATURE_EXTWDT_VALUE = 4,
+};
+
 /**
  * struct zynqmp_pm_query_data - PM query data
  * @qid:	query ID
@@ -416,6 +427,8 @@ int zynqmp_pm_pinctrl_get_config(const u32 pin, const u32 param,
 int zynqmp_pm_pinctrl_set_config(const u32 pin, const u32 param,
 				 u32 value);
 int zynqmp_pm_load_pdi(const u32 src, const u64 address);
+int zynqmp_pm_set_feature_config(enum pm_feature_config_id id, u32 value);
+int zynqmp_pm_get_feature_config(enum pm_feature_config_id id, u32 *payload);
 #else
 static inline int zynqmp_pm_get_api_version(u32 *version)
 {
@@ -632,6 +645,18 @@ static inline int zynqmp_pm_load_pdi(const u32 src, const u64 address)
 {
 	return -ENODEV;
 }
+
+static inline int zynqmp_pm_set_feature_config(enum pm_feature_config_id id,
+					       u32 value)
+{
+	return -ENODEV;
+}
+
+static inline int zynqmp_pm_get_feature_config(enum pm_feature_config_id id,
+					       u32 *payload)
+{
+	return -ENODEV;
+}
 #endif
 
 #endif /* __FIRMWARE_ZYNQMP_H__ */
-- 
2.32.0.93.g670b81a

[PATCH v2 2/3] firmware: zynqmp: Add sysfs entry for runtime features

[Ronak Jain]

Create sysfs entry for runtime feature configuration. The support
 is added for an over temperature and external watchdog feature.

The below listed files are used for runtime features configuration:
/sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
/sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value

In order to configure an over temperature or external watchdog
 features, first the user need to select the valid config id and then
 the user can configure the value for selected feature config id.

Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
---
Changes in v2:
- Update commit message
---
 .../ABI/stable/sysfs-driver-firmware-zynqmp   | 84 +++++++++++++++++++
 1 file changed, 84 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp b/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp
index f5724bb5b462..2fde354715a5 100644
--- a/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp
+++ b/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp
@@ -113,3 +113,87 @@ Description:
 		    # echo 0 > /sys/devices/platform/firmware\:zynqmp-firmware/health_status
 
 Users:		Xilinx
+
+What:		/sys/devices/platform/firmware\:zynqmp-firmware/feature_config_*
+Date:		Aug 2021
+KernelVersion:	5.14
+Contact:	"Ronak Jain" <ronak.jain@xilinx.com>
+Description:
+		This sysfs interface allows to configure features at runtime.
+		The user can enable or disable features running at firmware.
+		Also, the user can configure the parameters of the features
+		at runtime. The supported features are over temperature and
+		external watchdog. Here, the external watchdog is completely
+		different than the /dev/watchdog as the external watchdog is
+		running on the firmware and it is used to monitor the health
+		of firmware not APU(Linux). Also, the external watchdog is
+		interfaced outside of the zynqmp soc.
+
+		By default the features are disabled in the firmware. The user
+		can enable features by querying appropriate config id of the
+		features.
+
+		The default limit for the over temperature is 90 Degree Celsius.
+		The default timer interval for the external watchdog is 570ms.
+
+		The supported config ids are for the feature configuration is,
+		1. PM_FEATURE_OVERTEMP_STATUS = 1, the user can enable or
+		disable the over temperature feature.
+		2. PM_FEATURE_OVERTEMP_VALUE = 2, the user can configure the
+		over temperature limit in Degree Celsius.
+		3. PM_FEATURE_EXTWDT_STATUS = 3, the user can enable or disable
+		the external watchdog feature.
+		4. PM_FEATURE_EXTWDT_VALUE = 4, the user can configure the
+		external watchdog feature.
+
+		Usage:
+
+		Enable over temperature feature
+		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
+		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+
+		Check whether the over temperature feature is enabled or not
+		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+		The expected result is 1.
+
+		Disable over temperature feature
+		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
+		# echo 0 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+
+		Check whether the over temperature feature is disabled or not
+		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+		The expected result is 0.
+
+		Configure over temperature limit to 50 Degree Celsius
+		# echo 2 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
+		# echo 50 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+
+		Check whether the over temperature limit is configured or not
+		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+		The expected result is 50.
+
+		Enable external watchdog feature
+		# echo 3 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
+		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+
+		Check whether the external watchdog feature is enabled or not
+		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+		The expected result is 1.
+
+		Disable external watchdog feature
+		# echo 3 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
+		# echo 0 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+
+		Check whether the external watchdog feature is disabled or not
+		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+		The expected result is 0.
+
+		Configure external watchdog timer interval to 500ms
+		# echo 4 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
+		# echo 500 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+
+		Check whether the external watchdog timer interval is configured or not
+		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
+		The expected result is 500.
+
+Users:		Xilinx
-- 
2.32.0.93.g670b81a

Re: [PATCH v2 2/3] firmware: zynqmp: Add sysfs entry for runtime features

[Punit Agrawal]

Hi Ronak,

Ronak Jain <ronak.jain@xilinx.com> writes:

> Create sysfs entry for runtime feature configuration. The support
>  is added for an over temperature and external watchdog feature.
>
> The below listed files are used for runtime features configuration:
> /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
> /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
>
> In order to configure an over temperature or external watchdog
>  features, first the user need to select the valid config id and then
>  the user can configure the value for selected feature config id.
>
> Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
> ---
> Changes in v2:
> - Update commit message
> ---
>  .../ABI/stable/sysfs-driver-firmware-zynqmp   | 84 +++++++++++++++++++
>  1 file changed, 84 insertions(+)
>
> diff --git a/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp b/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp
> index f5724bb5b462..2fde354715a5 100644
> --- a/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp
> +++ b/Documentation/ABI/stable/sysfs-driver-firmware-zynqmp
> @@ -113,3 +113,87 @@ Description:
>  		    # echo 0 > /sys/devices/platform/firmware\:zynqmp-firmware/health_status
>  
>  Users:		Xilinx
> +
> +What:		/sys/devices/platform/firmware\:zynqmp-firmware/feature_config_*
> +Date:		Aug 2021
> +KernelVersion:	5.14
> +Contact:	"Ronak Jain" <ronak.jain@xilinx.com>
> +Description:
> +		This sysfs interface allows to configure features at runtime.
> +		The user can enable or disable features running at firmware.
> +		Also, the user can configure the parameters of the features
> +		at runtime. The supported features are over temperature and
> +		external watchdog. Here, the external watchdog is completely
> +		different than the /dev/watchdog as the external watchdog is
> +		running on the firmware and it is used to monitor the health
> +		of firmware not APU(Linux). Also, the external watchdog is
> +		interfaced outside of the zynqmp soc.
> +
> +		By default the features are disabled in the firmware. The user
> +		can enable features by querying appropriate config id of the
> +		features.
> +
> +		The default limit for the over temperature is 90 Degree Celsius.
> +		The default timer interval for the external watchdog is 570ms.
> +
> +		The supported config ids are for the feature configuration is,
> +		1. PM_FEATURE_OVERTEMP_STATUS = 1, the user can enable or
> +		disable the over temperature feature.
> +		2. PM_FEATURE_OVERTEMP_VALUE = 2, the user can configure the
> +		over temperature limit in Degree Celsius.
> +		3. PM_FEATURE_EXTWDT_STATUS = 3, the user can enable or disable
> +		the external watchdog feature.
> +		4. PM_FEATURE_EXTWDT_VALUE = 4, the user can configure the
> +		external watchdog feature.
> +
> +		Usage:
> +
> +		Enable over temperature feature
> +		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
> +		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +
> +		Check whether the over temperature feature is enabled or not
> +		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +		The expected result is 1.
> +
> +		Disable over temperature feature
> +		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
> +		# echo 0 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +
> +		Check whether the over temperature feature is disabled or not
> +		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +		The expected result is 0.
> +
> +		Configure over temperature limit to 50 Degree Celsius
> +		# echo 2 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
> +		# echo 50 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +
> +		Check whether the over temperature limit is configured or not
> +		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +		The expected result is 50.

Maybe I am missing something but I was wondering why these features are
being exposed via custom sysfs nodes - can they be integrated into the
respective subsystems?

e.g., Over temperature protection would fit in nicely with the thermal
sub-system. Did you explore integrating the feature there?

> +
> +		Enable external watchdog feature
> +		# echo 3 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
> +		# echo 1 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +
> +		Check whether the external watchdog feature is enabled or not
> +		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +		The expected result is 1.
> +
> +		Disable external watchdog feature
> +		# echo 3 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
> +		# echo 0 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +
> +		Check whether the external watchdog feature is disabled or not
> +		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +		The expected result is 0.
> +
> +		Configure external watchdog timer interval to 500ms
> +		# echo 4 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_id
> +		# echo 500 > /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +
> +		Check whether the external watchdog timer interval is configured or not
> +		# cat /sys/devices/platform/firmware\:zynqmp-firmware/feature_config_value
> +		The expected result is 500.

Similarly, this would make sense to go into the watchdog subsystem.

Using sub-system interfaces would allow existing tools to just work
without having to make zynqmp specific tools or find yet another way to
interact with these features. 

Thanks,
Punit

[PATCH v2 3/3] firmware: xilinx: Add sysfs support for feature config

[Ronak Jain]

Add support for sysfs interface for runtime features configuration.
 The user can configure the features at runtime. First the user need
 to select the config id of the supported features and then the user
 can configure the parameters of the feature based on the config id.
 So far the support is added for the over temperature and external
 watchdog features.

Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
---
Changes in v2:
- Update commit message
---
 drivers/firmware/xilinx/zynqmp.c | 71 ++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/drivers/firmware/xilinx/zynqmp.c b/drivers/firmware/xilinx/zynqmp.c
index 875d13bc1a57..a1434dd368f2 100644
--- a/drivers/firmware/xilinx/zynqmp.c
+++ b/drivers/firmware/xilinx/zynqmp.c
@@ -1361,6 +1361,75 @@ static DEVICE_ATTR_RW(pggs1);
 static DEVICE_ATTR_RW(pggs2);
 static DEVICE_ATTR_RW(pggs3);
 
+static atomic_t feature_conf_id;
+
+static ssize_t feature_config_id_show(struct device *device,
+				      struct device_attribute *attr,
+				      char *buf)
+{
+	return sysfs_emit(buf, "%d\n", atomic_read(&feature_conf_id));
+}
+
+static ssize_t feature_config_id_store(struct device *device,
+				       struct device_attribute *attr,
+				       const char *buf, size_t count)
+{
+	u32 config_id;
+	int ret;
+
+	if (!buf)
+		return -EINVAL;
+
+	ret = kstrtou32(buf, 10, &config_id);
+	if (ret)
+		return ret;
+
+	atomic_set(&feature_conf_id, config_id);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(feature_config_id);
+
+static ssize_t feature_config_value_show(struct device *device,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	int ret;
+	u32 ret_payload[PAYLOAD_ARG_CNT];
+
+	ret = zynqmp_pm_get_feature_config(atomic_read(&feature_conf_id),
+					   ret_payload);
+	if (ret)
+		return ret;
+
+	return sysfs_emit(buf, "%d\n", ret_payload[1]);
+}
+
+static ssize_t feature_config_value_store(struct device *device,
+					  struct device_attribute *attr,
+					  const char *buf, size_t count)
+{
+	u32 value;
+	int ret;
+
+	if (!buf)
+		return -EINVAL;
+
+	ret = kstrtou32(buf, 10, &value);
+	if (ret)
+		return ret;
+
+	ret = zynqmp_pm_set_feature_config(atomic_read(&feature_conf_id),
+					   value);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(feature_config_value);
+
 static struct attribute *zynqmp_firmware_attrs[] = {
 	&dev_attr_ggs0.attr,
 	&dev_attr_ggs1.attr,
@@ -1372,6 +1441,8 @@ static struct attribute *zynqmp_firmware_attrs[] = {
 	&dev_attr_pggs3.attr,
 	&dev_attr_shutdown_scope.attr,
 	&dev_attr_health_status.attr,
+	&dev_attr_feature_config_id.attr,
+	&dev_attr_feature_config_value.attr,
 	NULL,
 };
 
-- 
2.32.0.93.g670b81a

Re: [PATCH v2 3/3] firmware: xilinx: Add sysfs support for feature config

[Greg KH]

On Mon, Sep 13, 2021 at 01:39:55AM -0700, Ronak Jain wrote:
> Add support for sysfs interface for runtime features configuration.
>  The user can configure the features at runtime. First the user need
>  to select the config id of the supported features and then the user
>  can configure the parameters of the feature based on the config id.
>  So far the support is added for the over temperature and external
>  watchdog features.
> 
> Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
> ---
> Changes in v2:
> - Update commit message
> ---
>  drivers/firmware/xilinx/zynqmp.c | 71 ++++++++++++++++++++++++++++++++
>  1 file changed, 71 insertions(+)
> 
> diff --git a/drivers/firmware/xilinx/zynqmp.c b/drivers/firmware/xilinx/zynqmp.c
> index 875d13bc1a57..a1434dd368f2 100644
> --- a/drivers/firmware/xilinx/zynqmp.c
> +++ b/drivers/firmware/xilinx/zynqmp.c
> @@ -1361,6 +1361,75 @@ static DEVICE_ATTR_RW(pggs1);
>  static DEVICE_ATTR_RW(pggs2);
>  static DEVICE_ATTR_RW(pggs3);
>  
> +static atomic_t feature_conf_id;

Why does this have to be an atomic?

And shouldn't this be per-device, not global to all devices in the
system?

> +
> +static ssize_t feature_config_id_show(struct device *device,
> +				      struct device_attribute *attr,
> +				      char *buf)
> +{
> +	return sysfs_emit(buf, "%d\n", atomic_read(&feature_conf_id));
> +}
> +
> +static ssize_t feature_config_id_store(struct device *device,
> +				       struct device_attribute *attr,
> +				       const char *buf, size_t count)
> +{
> +	u32 config_id;
> +	int ret;
> +
> +	if (!buf)
> +		return -EINVAL;

How can there ever be a NULL buffer?

No need to check for impossible things.

thanks,

greg k-h

RE: [PATCH v2 3/3] firmware: xilinx: Add sysfs support for feature config

[Ronak Jain]

Hi Greg KH,

Thanks for reviewing.

> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: Tuesday, September 14, 2021 2:51 PM
> To: Ronak Jain <ronakj@xilinx.com>
> Cc: Michal Simek <michals@xilinx.com>; linux-kernel@vger.kernel.org; Rajan
> Vaja <RAJANV@xilinx.com>; corbet@lwn.net; linux-arm-
> kernel@lists.infradead.org; arnd@arndb.de; Sai Krishna Potthuri
> <lakshmis@xilinx.com>
> Subject: Re: [PATCH v2 3/3] firmware: xilinx: Add sysfs support for feature
> config
> 
> On Mon, Sep 13, 2021 at 01:39:55AM -0700, Ronak Jain wrote:
> > Add support for sysfs interface for runtime features configuration.
> >  The user can configure the features at runtime. First the user need
> > to select the config id of the supported features and then the user
> > can configure the parameters of the feature based on the config id.
> >  So far the support is added for the over temperature and external
> > watchdog features.
> >
> > Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
> > ---
> > Changes in v2:
> > - Update commit message
> > ---
> >  drivers/firmware/xilinx/zynqmp.c | 71
> > ++++++++++++++++++++++++++++++++
> >  1 file changed, 71 insertions(+)
> >
> > diff --git a/drivers/firmware/xilinx/zynqmp.c
> > b/drivers/firmware/xilinx/zynqmp.c
> > index 875d13bc1a57..a1434dd368f2 100644
> > --- a/drivers/firmware/xilinx/zynqmp.c
> > +++ b/drivers/firmware/xilinx/zynqmp.c
> > @@ -1361,6 +1361,75 @@ static DEVICE_ATTR_RW(pggs1);  static
> > DEVICE_ATTR_RW(pggs2);  static DEVICE_ATTR_RW(pggs3);
> >
> > +static atomic_t feature_conf_id;
> 
> Why does this have to be an atomic?
Use atomic to avoid race conditions. Suppose the case where the user is trying to write the variable and at the same time it tries to read, so there might be chances of occurrence of race condition. Also, I am not so sure whether the race condition will occur or not but just to prevent race condition I have used atomic variable so, the read/write operations can handle automatically.
> 
> And shouldn't this be per-device, not global to all devices in the system?
This is to store the config-id set by the user which will be used to retrieve config. There is only one firmware device so we can consider it systemwide. Please let me know if you think of a better way of handling it.
> 
> > +
> > +static ssize_t feature_config_id_show(struct device *device,
> > +				      struct device_attribute *attr,
> > +				      char *buf)
> > +{
> > +	return sysfs_emit(buf, "%d\n", atomic_read(&feature_conf_id)); }
> > +
> > +static ssize_t feature_config_id_store(struct device *device,
> > +				       struct device_attribute *attr,
> > +				       const char *buf, size_t count) {
> > +	u32 config_id;
> > +	int ret;
> > +
> > +	if (!buf)
> > +		return -EINVAL;
> 
> How can there ever be a NULL buffer?
> 
> No need to check for impossible things.
Will update in next version.

Thanks,
Ronak
> 
> thanks,
> 
> greg k-h

Re: [PATCH v2 3/3] firmware: xilinx: Add sysfs support for feature config

[Greg KH]

On Wed, Sep 15, 2021 at 06:16:16AM +0000, Ronak Jain wrote:
> Hi Greg KH,
> 
> Thanks for reviewing.
> 
> > -----Original Message-----
> > From: Greg KH <gregkh@linuxfoundation.org>
> > Sent: Tuesday, September 14, 2021 2:51 PM
> > To: Ronak Jain <ronakj@xilinx.com>
> > Cc: Michal Simek <michals@xilinx.com>; linux-kernel@vger.kernel.org; Rajan
> > Vaja <RAJANV@xilinx.com>; corbet@lwn.net; linux-arm-
> > kernel@lists.infradead.org; arnd@arndb.de; Sai Krishna Potthuri
> > <lakshmis@xilinx.com>
> > Subject: Re: [PATCH v2 3/3] firmware: xilinx: Add sysfs support for feature
> > config
> > 
> > On Mon, Sep 13, 2021 at 01:39:55AM -0700, Ronak Jain wrote:
> > > Add support for sysfs interface for runtime features configuration.
> > >  The user can configure the features at runtime. First the user need
> > > to select the config id of the supported features and then the user
> > > can configure the parameters of the feature based on the config id.
> > >  So far the support is added for the over temperature and external
> > > watchdog features.
> > >
> > > Signed-off-by: Ronak Jain <ronak.jain@xilinx.com>
> > > ---
> > > Changes in v2:
> > > - Update commit message
> > > ---
> > >  drivers/firmware/xilinx/zynqmp.c | 71
> > > ++++++++++++++++++++++++++++++++
> > >  1 file changed, 71 insertions(+)
> > >
> > > diff --git a/drivers/firmware/xilinx/zynqmp.c
> > > b/drivers/firmware/xilinx/zynqmp.c
> > > index 875d13bc1a57..a1434dd368f2 100644
> > > --- a/drivers/firmware/xilinx/zynqmp.c
> > > +++ b/drivers/firmware/xilinx/zynqmp.c
> > > @@ -1361,6 +1361,75 @@ static DEVICE_ATTR_RW(pggs1);  static
> > > DEVICE_ATTR_RW(pggs2);  static DEVICE_ATTR_RW(pggs3);
> > >
> > > +static atomic_t feature_conf_id;
> > 
> > Why does this have to be an atomic?
> Use atomic to avoid race conditions. Suppose the case where the user
> is trying to write the variable and at the same time it tries to read,
> so there might be chances of occurrence of race condition. Also, I am
> not so sure whether the race condition will occur or not but just to
> prevent race condition I have used atomic variable so, the read/write
> operations can handle automatically.

Reading/writing a single variable like this will not be a problem with
races.  If you care about stuff like this, just use a lock to protect
it, don't try to mess with an atomic if you do not have to have it.

> > And shouldn't this be per-device, not global to all devices in the system?
> This is to store the config-id set by the user which will be used to
> retrieve config. There is only one firmware device so we can consider
> it systemwide. Please let me know if you think of a better way of
> handling it.

So is it a device attribute or a driver attribute?

And you never know how many devices you have in a system, do not assume
you will not have multiple ones.  Use the proper structures to start
with and you never will have to change things in the future if you have
multiple devices.

thanks,

greg k-h