i2c: core: Add function for finding the bus speed from ACPI

[cascardo/linux.git] / drivers / i2c / i2c-core.c

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index abe4136..347494a 100644 (file)
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -105,11 +105,13 @@ struct gsb_buffer {
 
 struct i2c_acpi_lookup {
        struct i2c_board_info *info;
+       struct i2c_adapter *adapter; /* set only when registering slaves */
        acpi_handle adapter_handle;
        acpi_handle device_handle;
+       u32 min_speed;
 };
 
-static int i2c_acpi_find_address(struct acpi_resource *ares, void *data)
+static int i2c_acpi_find_resource(struct acpi_resource *ares, void *data)
 {
        struct i2c_acpi_lookup *lookup = data;
        struct i2c_board_info *info = lookup->info;
@@ -135,17 +137,20 @@ static int i2c_acpi_find_address(struct acpi_resource *ares, void *data)
                info->addr = sb->slave_address;
                if (sb->access_mode == ACPI_I2C_10BIT_MODE)
                        info->flags |= I2C_CLIENT_TEN;
+               /* Save speed of the slowest device */
+               if (sb->connection_speed < lookup->min_speed)
+                       lookup->min_speed = sb->connection_speed;
        }
 
        return 1;
 }
 
-static acpi_status i2c_acpi_add_device(acpi_handle handle, u32 level,
-                                      void *data, void **return_value)
+static acpi_status i2c_acpi_slave_lookup(acpi_handle handle, u32 level,
+                                        void *data, void **return_value)
 {
-       struct i2c_adapter *adapter = data;
+       struct i2c_acpi_lookup *lookup = data;
+       struct i2c_adapter *adapter = lookup->adapter;
        struct list_head resource_list;
-       struct i2c_acpi_lookup lookup;
        struct resource_entry *entry;
        struct i2c_board_info info;
        struct acpi_device *adev;
@@ -159,10 +164,8 @@ static acpi_status i2c_acpi_add_device(acpi_handle handle, u32 level,
        memset(&info, 0, sizeof(info));
        info.fwnode = acpi_fwnode_handle(adev);
 
-       memset(&lookup, 0, sizeof(lookup));
-       lookup.adapter_handle = ACPI_HANDLE(&adapter->dev);
-       lookup.device_handle = handle;
-       lookup.info = &info;
+       lookup->device_handle = handle;
+       lookup->info = &info;
 
        /*
         * Look up for I2cSerialBus resource with ResourceSource that
@@ -170,10 +173,10 @@ static acpi_status i2c_acpi_add_device(acpi_handle handle, u32 level,
         */
        INIT_LIST_HEAD(&resource_list);
        ret = acpi_dev_get_resources(adev, &resource_list,
-                                    i2c_acpi_find_address, &lookup);
+                                    i2c_acpi_find_resource, lookup);
        acpi_dev_free_resource_list(&resource_list);
 
-       if (ret < 0 || !info.addr)
+       if (ret < 0 || !info.addr || !lookup->adapter)
                return AE_OK;
 
        /* Then fill IRQ number if any */
@@ -204,6 +207,14 @@ static acpi_status i2c_acpi_add_device(acpi_handle handle, u32 level,
 
 #define I2C_ACPI_MAX_SCAN_DEPTH 32
 
+static acpi_status i2c_acpi_walk(struct i2c_acpi_lookup *lookup)
+{
+       return acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+                                  I2C_ACPI_MAX_SCAN_DEPTH,
+                                  i2c_acpi_slave_lookup, NULL,
+                                  lookup, NULL);
+}
+
 /**
  * i2c_acpi_register_devices - enumerate I2C slave devices behind adapter
  * @adap: pointer to adapter
@@ -214,19 +225,52 @@ static acpi_status i2c_acpi_add_device(acpi_handle handle, u32 level,
  */
 static void i2c_acpi_register_devices(struct i2c_adapter *adap)
 {
+       struct i2c_acpi_lookup lookup;
        acpi_status status;
 
        if (!has_acpi_companion(&adap->dev))
                return;
 
-       status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
-                                    I2C_ACPI_MAX_SCAN_DEPTH,
-                                    i2c_acpi_add_device, NULL,
-                                    adap, NULL);
+       memset(&lookup, 0, sizeof(lookup));
+       lookup.adapter = adap;
+       lookup.adapter_handle = ACPI_HANDLE(&adap->dev);
+
+       status = i2c_acpi_walk(&lookup);
        if (ACPI_FAILURE(status))
                dev_warn(&adap->dev, "failed to enumerate I2C slaves\n");
 }
 
+/**
+ * i2c_acpi_find_bus_speed - find I2C bus speed from ACPI
+ * @dev: The device owning the bus
+ *
+ * Find the I2C bus speed by walking the ACPI namespace for all I2C slaves
+ * devices connected to this bus and use the speed of slowest device.
+ *
+ * Returns the speed in Hz or zero
+ */
+u32 i2c_acpi_find_bus_speed(struct device *dev)
+{
+       struct i2c_acpi_lookup lookup;
+       acpi_status status;
+
+       if (!has_acpi_companion(dev))
+               return 0;
+
+       memset(&lookup, 0, sizeof(lookup));
+       lookup.adapter_handle = ACPI_HANDLE(dev);
+       lookup.min_speed = UINT_MAX;
+
+       status = i2c_acpi_walk(&lookup);
+       if (ACPI_FAILURE(status)) {
+               dev_warn(dev, "unable to find I2C bus speed from ACPI\n");
+               return 0;
+       }
+
+       return lookup.min_speed != UINT_MAX ? lookup.min_speed : 0;
+}
+EXPORT_SYMBOL_GPL(i2c_acpi_find_bus_speed);
+
 #else /* CONFIG_ACPI */
 static inline void i2c_acpi_register_devices(struct i2c_adapter *adap) { }
 #endif /* CONFIG_ACPI */