Re: [RFC PATCH] ACPI: Add _DEP(Operation Region Dependencies) support to fix battery issue on the Asus T100TA

[Lan Tianyu]

On 2014å09æ25æ 06:27, Rafael J. Wysocki wrote:
> On Tuesday, September 23, 2014 03:06:43 PM Lan Tianyu wrote:
>> ACPI 5.0 introduces _DEP to designate device objects that OSPM should
>> assign a higher priority in start ordering due to future operation region
>> accesses.
>>
>> On Asus T100TA, ACPI battery info are read from a I2C slave device via
>> I2C operation region. Before I2C operation region handler is installed,
>> battery _STA always returns 0. There is a _DEP method of designating
>> start order under battery device node.
>>
>> This patch is to implement _DEP feature to fix battery issue on the Asus T100TA.
>> Introducing acpi_bus_dep_device_list and adding dep_present flags in the struct
>> acpi_device. During ACPI namespace scan, all devices with _DEP support will be put
>> into the new list and those devices' dep_present flag will be set. Driver's probe()
>> should return EPROBE_DEFER when find dep_present is set. When I2C operation
>> region handler is installed, check all devices on the new list. Remove the one from
>> list if _DEP condition is met and clear its dep_present flag and do acpi_bus_attch()
>> for the device in order to resolve battery _STA issue on the Asus T100TA.
>>
>> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
> 
> This is going in the right direction in my view, but isn't there just yet.
> 
> Details below.

Thanks for review.

> 
>> ---
>>  drivers/acpi/battery.c  |  4 +++
>>  drivers/acpi/scan.c     | 84 +++++++++++++++++++++++++++++++++++++++++++++++++
>>  drivers/i2c/i2c-acpi.c  |  1 +
>>  include/acpi/acpi_bus.h |  2 ++
>>  include/linux/acpi.h    |  3 ++
>>  5 files changed, 94 insertions(+)
>>
>> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
>> index 1c162e7..c0a68ce 100644
>> --- a/drivers/acpi/battery.c
>> +++ b/drivers/acpi/battery.c
>> @@ -1194,6 +1194,10 @@ static int acpi_battery_add(struct acpi_device *device)
>>  
>>  	if (!device)
>>  		return -EINVAL;
>> +
>> +	if (device->dep_present)
> 
> device->flags.dep_present would be better.  Or even call the flag dep_unmet.

Ok. Will update.

> 
>> +		return -EPROBE_DEFER;
>> +
>>  	battery = kzalloc(sizeof(struct acpi_battery), GFP_KERNEL);
>>  	if (!battery)
>>  		return -ENOMEM;
>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index 3bf7764..a26dbb3 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -36,6 +36,7 @@ bool acpi_force_hot_remove;
>>  
>>  static const char *dummy_hid = "device";
>>  
>> +static LIST_HEAD(acpi_bus_dep_device_list);
>>  static LIST_HEAD(acpi_bus_id_list);
>>  static DEFINE_MUTEX(acpi_scan_lock);
>>  static LIST_HEAD(acpi_scan_handlers_list);
>> @@ -43,6 +44,11 @@ DEFINE_MUTEX(acpi_device_lock);
>>  LIST_HEAD(acpi_wakeup_device_list);
>>  static DEFINE_MUTEX(acpi_hp_context_lock);
>>  
>> +struct acpi_dep_data {
>> +	struct list_head node;
>> +	struct acpi_device *adev;
>> +};
>> +
>>  struct acpi_device_bus_id{
>>  	char bus_id[15];
>>  	unsigned int instance_no;
>> @@ -2048,6 +2054,32 @@ static void acpi_scan_init_hotplug(struct acpi_device *adev)
>>  	}
>>  }
>>  
>> +static void acpi_device_dep_initialize(struct acpi_device * adev)
>> +{
>> +	struct acpi_dep_data *dep;
>> +	acpi_status status;
>> +
>> +	if (!acpi_has_method(adev->handle, "_DEP"))
>> +		return;
>> +
>> +	status = acpi_evaluate_reference(adev->handle, "_DEP", NULL,
>> +					&adev->dep_devices);
>> +	if (ACPI_FAILURE(status)) {
>> +		dev_err(&adev->dev, "Fail to evaluate _DEP.\n");
> 
> "Failed"
> 
>> +		return;
>> +	}
>> +
>> +	dep = kzalloc(sizeof(struct acpi_dep_data), GFP_KERNEL);
>> +	if (!dep) {
>> +		dev_err(&adev->dev, "Memory allocation error.\n");
> 
> "Not enough memory for _DEP list entry\n"
> 
>> +		return;
>> +	}
>> +
>> +	dep->adev = adev;
>> +	adev->dep_present = true;
>> +	list_add_tail(&dep->node , &acpi_bus_dep_device_list);
>> +}
>> +
>>  static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl_not_used,
>>  				      void *not_used, void **return_value)
>>  {
>> @@ -2074,6 +2106,7 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl_not_used,
>>  		return AE_CTRL_DEPTH;
>>  
>>  	acpi_scan_init_hotplug(device);
>> +	acpi_device_dep_initialize(device);
>>  
>>   out:
>>  	if (!*return_value)
>> @@ -2191,6 +2224,57 @@ static void acpi_bus_attach(struct acpi_device *device)
>>  		acpi_bus_attach(child);
>>  }
>>  
>> +static int acpi_device_dep_check(struct acpi_device *adev)
>> +{
>> +	struct acpi_device *dep_adev;
>> +	struct acpi_device_physical_node *pn;
>> +	int i;
>> +
>> +	for (i = 0; i < adev->dep_devices.count; i++) {
>> +		dep_adev = acpi_bus_get_acpi_device(
>> +				adev->dep_devices.handles[i]);
>> +
>> +		if (!dep_adev)
>> +			return -ENODEV;
>> +
>> +		/* Check acpi device driver probing */
>> +		if (dep_adev->dev.driver)
>> +			continue;
> 
> This check isn't sufficient, because _DEP is supposed to be about operation
> regions being present, not about drivers being present.  Same for the driver
> check below.
> 
> I wouldn't bother to check drivers in this stub implementation. ->

Sounds like we need to check whether the dependent device node has been
attached with operation region handler and this needs ACPICA to expose
such function, right?

> 
>> +
>> +		if (!dep_adev->physical_node_count)
>> +			return -ENODEV;
>> +
>> +		/* Check physcial device node driver probing */
>> +		mutex_lock(&dep_adev->physical_node_lock);
>> +		list_for_each_entry(pn, &dep_adev->physical_node_list, node) {
>> +			if (pn->dev->driver) {
>> +				mutex_unlock(&dep_adev->physical_node_lock);
>> +				continue;
>> +			}
>> +		}
>> +		mutex_unlock(&dep_adev->physical_node_lock);
>> +		return -EFAULT;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +int acpi_walk_dep_device_list(void)
> 
> -> I'd pass the operation region device to that (and I'd call the function
> differently, but that's a detail).  Then, I'd just clear flags.dep_unmet
> for all devices having that operation region device in their dep_devices
> (and drop their entries from the list).  It wouldn't cover the case when
> one device depends on two operation regions at the same time (in a meaningful
> way), but should be sufficient to address the battery problem at hand. 
> 

This requires the dependent devices have a list to record devices which
depends on them, right? Create such lists during ACPI namespace scan.


>> +{
>> +	struct acpi_dep_data *dep, *tmp;
>> +
>> +	list_for_each_entry_safe(dep, tmp, &acpi_bus_dep_device_list, node) {
>> +		if (!acpi_device_dep_check(dep->adev)) {
>> +			dep->adev->dep_present = false;
>> +			acpi_bus_attach(dep->adev);
>> +			list_del(&dep->node);
>> +			kfree(dep);
>> +		}
>> +	}
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(acpi_walk_dep_device_list);
>> +
>>  /**
>>   * acpi_bus_scan - Add ACPI device node objects in a given namespace scope.
>>   * @handle: Root of the namespace scope to scan.
>> diff --git a/drivers/i2c/i2c-acpi.c b/drivers/i2c/i2c-acpi.c
>> index 0dbc18c..fdc8dc8 100644
>> --- a/drivers/i2c/i2c-acpi.c
>> +++ b/drivers/i2c/i2c-acpi.c
>> @@ -339,6 +339,7 @@ int acpi_i2c_install_space_handler(struct i2c_adapter *adapter)
>>  		return -ENOMEM;
>>  	}
>>  
>> +	acpi_walk_dep_device_list();
>>  	return 0;
>>  }
>>  
>> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
>> index c1c9de1..c1e7055 100644
>> --- a/include/acpi/acpi_bus.h
>> +++ b/include/acpi/acpi_bus.h
>> @@ -357,7 +357,9 @@ struct acpi_device {
>>  	struct acpi_hotplug_context *hp;
>>  	struct acpi_driver *driver;
>>  	void *driver_data;
>> +	bool dep_present;
>>  	struct device dev;
>> +	struct acpi_handle_list dep_devices;
>>  	unsigned int physical_node_count;
>>  	struct list_head physical_node_list;
>>  	struct mutex physical_node_lock;
>> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> index 807cbc4..c9a504b 100644
>> --- a/include/linux/acpi.h
>> +++ b/include/linux/acpi.h
>> @@ -431,6 +431,7 @@ static inline bool acpi_driver_match_device(struct device *dev,
>>  
>>  int acpi_device_uevent_modalias(struct device *, struct kobj_uevent_env *);
>>  int acpi_device_modalias(struct device *, char *, int);
>> +int acpi_walk_dep_device_list(void);
>>  
>>  #define ACPI_PTR(_ptr)	(_ptr)
>>  
>> @@ -449,6 +450,8 @@ static inline const char *acpi_dev_name(struct acpi_device *adev)
>>  
>>  static inline void acpi_early_init(void) { }
>>  
>> +static inline int acpi_walk_dep_device_list(void) { }
>> +
>>  static inline int early_acpi_boot_init(void)
>>  {
>>  	return 0;
>>
> 


-- 
Best regards
Tianyu Lan
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