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

From: Rafael J. Wysocki
Date: Wed Sep 24 2014 - 18:07:50 EST

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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/