Re: [PATCH 4/4] drivers/hwmon/pmbus: Add debugfs for status registers

[Eddie James <eajames@linux.vnet.ibm.com>]

On 08/09/2017 08:15 PM, Guenter Roeck wrote:
> On Wed, Aug 09, 2017 at 05:19:17PM -0500, Eddie James wrote:
>> From: "Edward A. James" <eajames@us.ibm.com>
>>
>> Export all the available status registers through debugfs, if the client
>> driver wants them.
>>
>> Signed-off-by: Edward A. James <eajames@us.ibm.com>
>> ---
>>   drivers/hwmon/pmbus/pmbus.c      |  24 +++++-
>>   drivers/hwmon/pmbus/pmbus.h      |  11 +++
>>   drivers/hwmon/pmbus/pmbus_core.c | 175 +++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 209 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hwmon/pmbus/pmbus.c b/drivers/hwmon/pmbus/pmbus.c
>> index 7718e58..fc27417 100644
>> --- a/drivers/hwmon/pmbus/pmbus.c
>> +++ b/drivers/hwmon/pmbus/pmbus.c
> That won't work: SENSORS_PMBUS is independent of PMBUS and does not have
> to be enabled even if PMBUS is enabled. This will have to be in pmbus_core.c.
>
> I would suggest to do the same as done with other drivers. Move
> pmbus_debugfs_dir into pmbus_core.c and create the directory on probe
> if it has not already been created.

Hmm, I'm having trouble with this. Don't I have to call 
debugfs_recursive_remove() on the pmbus_debugfs_dir when the pmbus 
driver is unloaded? That can't be done from pmbus_core.c, as that is 
just device probe/remove. I agree it makes sense to only create it if a 
device is going to be using it (and is enabled in the kernel) but I 
think I need to declare it here so I can remove it on unload.

>
>> @@ -18,6 +18,7 @@
>>    * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>>    */
>>   
>> +#include <linux/debugfs.h>
>>   #include <linux/kernel.h>
>>   #include <linux/module.h>
>>   #include <linux/init.h>
>> @@ -230,7 +231,28 @@ static int pmbus_probe(struct i2c_client *client,
>>   	.id_table = pmbus_id,
>>   };
>>   
>> -module_i2c_driver(pmbus_driver);
>> +struct dentry *pmbus_debugfs_dir;
>> +EXPORT_SYMBOL_GPL(pmbus_debugfs_dir);
>> +
>> +static int __init pmbus_init(void)
>> +{
>> +	pmbus_debugfs_dir = debugfs_create_dir(pmbus_driver.driver.name, NULL);
>> +	if (IS_ERR(pmbus_debugfs_dir))
>> +		/* Don't fail out if we don't have debugfs support. */
>> +		pmbus_debugfs_dir = NULL;
>> +
>> +	return i2c_add_driver(&pmbus_driver);
>> +}
>> +
>> +static void __exit pmbus_exit(void)
>> +{
>> +	debugfs_remove_recursive(pmbus_debugfs_dir);
>> +
>> +	i2c_del_driver(&pmbus_driver);
>> +}
>> +
>> +module_init(pmbus_init);
>> +module_exit(pmbus_exit);
>>   
>>   MODULE_AUTHOR("Guenter Roeck");
>>   MODULE_DESCRIPTION("Generic PMBus driver");
>> diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
>> index bfcb13b..c772b83 100644
>> --- a/drivers/hwmon/pmbus/pmbus.h
>> +++ b/drivers/hwmon/pmbus/pmbus.h
>> @@ -25,6 +25,8 @@
>>   #include <linux/bitops.h>
>>   #include <linux/regulator/driver.h>
>>   
>> +struct dentry;
>> +
>>   /*
>>    * Registers
>>    */
>> @@ -383,6 +385,12 @@ struct pmbus_driver_info {
>>   	/* Regulator functionality, if supported by this chip driver. */
>>   	int num_regulators;
>>   	const struct regulator_desc *reg_desc;
>> +
>> +	/*
>> +	 * Controls whether or not to create debugfs entries for this driver's
>> +	 * devices.
>> +	 */
>> +	bool debugfs;
>>   };
>>   
>>   /* Regulator ops */
>> @@ -401,6 +409,9 @@ struct pmbus_driver_info {
>>   		.owner = THIS_MODULE,				\
>>   	}
>>   
>> +/* Handle for debugfs directory */
>> +extern struct dentry *pmbus_debugfs_dir;
>> +
>>   /* Function declarations */
>>   
>>   void pmbus_clear_cache(struct i2c_client *client);
>> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
>> index 1a51f8f..afbd364 100644
>> --- a/drivers/hwmon/pmbus/pmbus_core.c
>> +++ b/drivers/hwmon/pmbus/pmbus_core.c
>> @@ -19,6 +19,7 @@
>>    * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>>    */
>>   
>> +#include <linux/debugfs.h>
>>   #include <linux/kernel.h>
>>   #include <linux/module.h>
>>   #include <linux/init.h>
>> @@ -49,6 +50,9 @@
>>   #define PB_STATUS_FAN34_BASE	(PB_STATUS_FAN_BASE + PMBUS_PAGES)
>>   #define PB_STATUS_TEMP_BASE	(PB_STATUS_FAN34_BASE + PMBUS_PAGES)
>>   #define PB_STATUS_INPUT_BASE	(PB_STATUS_TEMP_BASE + PMBUS_PAGES)
>> +#define PB_STATUS_CML_BASE	(PB_STATUS_INPUT_BASE + PMBUS_PAGES)
>> +#define PB_STATUS_OTHER_BASE	(PB_STATUS_CML_BASE + PMBUS_PAGES)
>> +#define PB_STATUS_MFR_BASE	(PB_STATUS_OTHER_BASE + PMBUS_PAGES)
> We are not actively using those status registers, are we ?
> I am a bit concerned that we'll continuously read those status registers
> but don't do anything with it most of the time. Ultimately I'd prefer
> to get rid of all caching, not more, since it gets quite expensive
> on chips with many pages.
>
> Maybe just display uncached status register values in debugfs ?

Sounds good.

>
>>   #define PB_STATUS_VMON_BASE	(PB_STATUS_INPUT_BASE + 1)
>>   
>>   #define PB_NUM_STATUS_REG	(PB_STATUS_VMON_BASE + 1)
>> @@ -101,6 +105,7 @@ struct pmbus_data {
>>   	int num_attributes;
>>   	struct attribute_group group;
>>   	const struct attribute_group *groups[2];
>> +	struct dentry *debugfs;		/* debugfs device directory */
>>   
>>   	struct pmbus_sensor *sensors;
>>   
>> @@ -119,6 +124,11 @@ struct pmbus_data {
>>   	u8 currpage;
>>   };
>>   
>> +struct pmbus_debugfs_entry {
>> +	struct device *dev;
>> +	int index;
>> +};
>> +
>>   void pmbus_clear_cache(struct i2c_client *client)
>>   {
>>   	struct pmbus_data *data = i2c_get_clientdata(client);
>> @@ -422,6 +432,19 @@ static struct pmbus_data *pmbus_update_device(struct device *dev)
>>   					= _pmbus_read_byte_data(client, i,
>>   								s->reg);
>>   			}
>> +
>> +			if (!data->debugfs)
>> +				continue;
>> +
>> +			data->status[PB_STATUS_CML_BASE + i]
>> +				= _pmbus_read_byte_data(client, i,
>> +							PMBUS_STATUS_CML);
>> +			data->status[PB_STATUS_OTHER_BASE + i]
>> +				= _pmbus_read_byte_data(client, i,
>> +							PMBUS_STATUS_OTHER);
>> +			data->status[PB_STATUS_MFR_BASE + i]
>> +			    = _pmbus_read_byte_data(client, i,
>> +						    PMBUS_STATUS_MFR_SPECIFIC);
>>   		}
>>   
>>   		if (info->func[0] & PMBUS_HAVE_STATUS_INPUT)
>> @@ -1891,6 +1914,151 @@ static int pmbus_regulator_register(struct pmbus_data *data)
>>   }
>>   #endif
>>   
>> +static int pmbus_debugfs_get(void *data, u64 *val)
>> +{
>> +	struct pmbus_debugfs_entry *entry = data;
>> +	struct pmbus_data *pdata = pmbus_update_device(entry->dev);
>> +
>> +	*val = pdata->status[entry->index];
>> +
>> +	return 0;
>> +}
>> +
>> +DEFINE_DEBUGFS_ATTRIBUTE(pmbus_debugfs_ops8, pmbus_debugfs_get, NULL,
>> +			 "0x%02llx\n");
>> +DEFINE_DEBUGFS_ATTRIBUTE(pmbus_debugfs_ops16, pmbus_debugfs_get, NULL,
>> +			 "0x%04llx\n");
>> +
>> +static int pmbus_init_debugfs(struct i2c_client *client,
>> +			      struct pmbus_data *data)
>> +{
>> +	int i, idx = 0;
>> +	struct dentry *dbg;
>> +	char name[PMBUS_NAME_SIZE];
>> +	struct pmbus_debugfs_entry *entries;
>> +
>> +	/*
>> +	 * Either user didn't request debugfs or debugfs is not enabled in
>> +	 * kernel. Exit but don't throw an error in these cases.
>> +	 */
> Here might be the place to initialize pmbus_debugfs_dir
> if it is not yet initialized.
>
>> +	if (!data->info->debugfs || !pmbus_debugfs_dir)
>> +		return 0;
>> +
>> +	/*
>> +	 * Create the debugfs directory for this device. Use the hwmon device
>> +	 * name to avoid conflicts (hwmon numbers are globally unique).
>> +	 */
>> +	data->debugfs = debugfs_create_dir(dev_name(data->hwmon_dev),
>> +					   pmbus_debugfs_dir);
>> +	if (IS_ERR_OR_NULL(data->debugfs)) {
>> +		data->debugfs = NULL;
>> +		return -ENODEV;
>> +	}
>> +
>> +	/* Allocate the max possible entries we need. */
>> +	entries = devm_kzalloc(data->dev,
>> +			       sizeof(*entries) * (data->info->pages * 10),
>> +			       GFP_KERNEL);
>> +	if (!entries)
>> +		return -ENOMEM;
>> +
>> +	for (i = 0; i < data->info->pages; ++i) {
>> +		/* check accessibility of status register if it's not page 0 */
>> +		if (!i || pmbus_check_status_register(client, i)) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops16);
> What is the point of the dbg variable ?
>
>> +		}
>> +
>> +		if (data->info->func[i] & PMBUS_HAVE_STATUS_VOUT) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_VOUT_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_vout", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (data->info->func[i] & PMBUS_HAVE_STATUS_IOUT) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_IOUT_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_iout", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (data->info->func[i] & PMBUS_HAVE_STATUS_INPUT) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_INPUT_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_input", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (data->info->func[i] & PMBUS_HAVE_STATUS_TEMP) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_TEMP_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_temp", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (pmbus_check_byte_register(client, i, PMBUS_STATUS_CML)) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_CML_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_cml", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (pmbus_check_byte_register(client, i, PMBUS_STATUS_OTHER)) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_OTHER_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_other", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (pmbus_check_byte_register(client, i,
>> +					      PMBUS_STATUS_MFR_SPECIFIC)) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_MFR_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_mfr", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (data->info->func[i] & PMBUS_HAVE_STATUS_FAN12) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_FAN_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_fan12", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +
>> +		if (data->info->func[i] & PMBUS_HAVE_STATUS_FAN34) {
>> +			entries[idx].dev = data->hwmon_dev;
>> +			entries[idx].index = PB_STATUS_FAN34_BASE + i;
>> +			snprintf(name, PMBUS_NAME_SIZE, "status%d_fan34", i);
>> +			dbg = debugfs_create_file(name, 0444, data->debugfs,
>> +						  &entries[idx++],
>> +						  &pmbus_debugfs_ops8);
>> +		}
>> +	}
>> +
>> +	return 0;
>> +}
>> +
> Typically debugfs code is conditional. What happens if DEBUGFS
> is not enabled ? See below.
>
>>   int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
>>   		   struct pmbus_driver_info *info)
>>   {
>> @@ -1950,6 +2118,10 @@ int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
>>   	if (ret)
>>   		goto out_unregister;
>>   
>> +	ret = pmbus_init_debugfs(client, data);
>> +	if (ret)
>> +		dev_warn(dev, "Failed to register debugfs\n");
> I think this warning will be generated if debugfs is disabled.
> We should not do that. Consider putting the debugfs code into
> #fidef and have a dummy pmbus_init_debugfs() returning 0 if
> it is disabled.

Yes, good idea.

>
>> +
>>   	return 0;
>>   
>>   out_unregister:
>> @@ -1963,6 +2135,9 @@ int pmbus_do_probe(struct i2c_client *client, const struct i2c_device_id *id,
>>   int pmbus_do_remove(struct i2c_client *client)
>>   {
>>   	struct pmbus_data *data = i2c_get_clientdata(client);
>> +
>> +	debugfs_remove_recursive(data->debugfs);
>> +
>>   	hwmon_device_unregister(data->hwmon_dev);
>>   	kfree(data->group.attrs);
>>   	return 0;
>> -- 
>> 1.8.3.1
>>
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