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

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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.

> ---
>  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.

> +		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. ->

> +
> +		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. 

> +{
> +	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;
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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