[PATCH 1/2] i2c/ACPI: Support for multiple serial bus addresses

[Srinivas Pandruvada]

ACPI specification allows multiple i2c addresses defined under one
ACPI device object. These addresses are defined using _CRS method.
The current implementation will pickup the last entry in _CRS, and
create an i2C device, ignoring all other previous entries for addresses.

The ACPI specification does not define, whether these addresses for one
i2c device or for multiple i2c devices, which are defined under the same
ACPI device object. We need some appoach where i2c clients can enumerate
on each of the i2C address and/or have access to those extra addresses.

This change addresses both cases:
- Create a new i2c device for each i2c address
- Allow each i2 client to get addresses of all other devices under
the same ACPI device object (companions or siblings)

Example 1:
Here in the following example, there are two i2C address in _CRS.
They belong to two different physical chipsets, with two different i2c
address but part of a module.
Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
{
        Name (RBUF, ResourceTemplate ()
        {
		I2cSerialBus (0x0068, ControllerInitiated, 0x00061A80,
			AddressingMode7Bit, "\\_SB.I2C5",
			0x00, ResourceConsumer, ,
		)
		I2cSerialBus (0x000C, ControllerInitiated, 0x00061A80,
			AddressingMode7Bit, "\\_SB.I2C5",
			0x00, ResourceConsumer, ,
		)
		Interrupt (ResourceConsumer, Level, ActiveHigh, Shared, ,, )
		{
			0x00000044,
		}
	})
	Return (RBUF)
}
This change adds i2c_new_device for each i2c address. Here contents of
/sys/bus/i2c/devices will
	i2c-some_acpi_dev_name:00:068
	i2c-some_acpi_dev_name::00:00c

Example 2

Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
                {
                    Name (SBUF, ResourceTemplate ()
                    {
                        GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly,
                            "\\_SB.GPO1", 0x00, ResourceConsumer, ,
                            )
                            {   // Pin list
                                0x0018
                            }
                        I2cSerialBus (0x0010, ControllerInitiated, 0x00061A80,
                            AddressingMode7Bit, "\\_SB.I2C4",
                            0x00, ResourceConsumer, ,
                            )
                        I2cSerialBus (0x000C, ControllerInitiated, 0x00061A80,
                            AddressingMode7Bit, "\\_SB.I2C4",
                            0x00, ResourceConsumer, ,
                            )
                        I2cSerialBus (0x0054, ControllerInitiated, 0x00061A80,
                            AddressingMode7Bit, "\\_SB.I2C4",
                            0x00, ResourceConsumer, ,
                            )
                    })
                    Return (SBUF) /* \_SB_.I2C4.CAM1._CRS.SBUF */
                }
}
Here there are three i2c addresses for this device.

When there is only I2cSerialBus address is present then there is no
change. The device name will not include address. In this way if
some device is using hardcoded path, this change will not impact them.

Here any i2c client driver simply need to add ACPI bindings. They will
be probed multiple times, the client will bind to correct i2c device,
based on checking its identity and returning error for other.
At the same time, any i2c client can call i2c_for_each_acpi_comp_client
to get the i2c client instances of companion addresses defined
under the same ACPI device.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
---
 drivers/i2c/i2c-core.c | 111 ++++++++++++++++++++++++++++++++++++++++++-------
 include/linux/i2c.h    |  13 ++++++
 2 files changed, 109 insertions(+), 15 deletions(-)

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 5fb80b8..a69a7b4 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -627,7 +627,7 @@ static void i2c_dev_set_name(struct i2c_adapter *adap,
 	struct acpi_device *adev = ACPI_COMPANION(&client->dev);
 
 	if (adev) {
-		dev_set_name(&client->dev, "i2c-%s", acpi_dev_name(adev));
+		dev_set_name(&client->dev, "i2c-%s", client->name);
 		return;
 	}
 
@@ -1080,24 +1080,44 @@ static void of_i2c_register_devices(struct i2c_adapter *adap) { }
 /* ACPI support code */
 
 #if IS_ENABLED(CONFIG_ACPI)
+/*
+ * acpi_i2c_add_resource is a callback, which is called while walking
+ * name spaces, adding a limit allows for faster processing, without
+ * using reallocation,
+ * Adding some limit for max adresses in resource. Currently we see
+ * max only 3 addresses, so 20 is more than enough
+ */
+#define MAX_CRS_ELEMENTS	20
+struct i2c_resource_info {
+	unsigned short addr[MAX_CRS_ELEMENTS];
+	unsigned short flags[MAX_CRS_ELEMENTS];
+	int count;
+	int common_irq;
+};
+
 static int acpi_i2c_add_resource(struct acpi_resource *ares, void *data)
 {
-	struct i2c_board_info *info = data;
+	struct i2c_resource_info *rcs_info = data;
 
 	if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS) {
 		struct acpi_resource_i2c_serialbus *sb;
 
 		sb = &ares->data.i2c_serial_bus;
 		if (sb->type == ACPI_RESOURCE_SERIAL_TYPE_I2C) {
-			info->addr = sb->slave_address;
+			if (rcs_info->count >= MAX_CRS_ELEMENTS)
+				return 1; /* Simply ignore adding */
+			rcs_info->addr[rcs_info->count] =
+							sb->slave_address;
 			if (sb->access_mode == ACPI_I2C_10BIT_MODE)
-				info->flags |= I2C_CLIENT_TEN;
+				rcs_info->flags[rcs_info->count] =
+								I2C_CLIENT_TEN;
+			rcs_info->count++;
 		}
-	} else if (info->irq < 0) {
+	} else if (rcs_info->common_irq < 0) {
 		struct resource r;
 
 		if (acpi_dev_resource_interrupt(ares, 0, &r))
-			info->irq = r.start;
+			rcs_info->common_irq = r.start;
 	}
 
 	/* Tell the ACPI core to skip this resource */
@@ -1111,7 +1131,10 @@ static acpi_status acpi_i2c_add_device(acpi_handle handle, u32 level,
 	struct list_head resource_list;
 	struct i2c_board_info info;
 	struct acpi_device *adev;
+	struct i2c_resource_info rcs_info;
+	struct i2c_client *i2c_client;
 	int ret;
+	int i;
 
 	if (acpi_bus_get_device(handle, &adev))
 		return AE_OK;
@@ -1120,23 +1143,42 @@ static acpi_status acpi_i2c_add_device(acpi_handle handle, u32 level,
 
 	memset(&info, 0, sizeof(info));
 	info.acpi_node.companion = adev;
-	info.irq = -1;
+
+	memset(&rcs_info, 0, sizeof(rcs_info));
+	rcs_info.common_irq = -1;
 
 	INIT_LIST_HEAD(&resource_list);
 	ret = acpi_dev_get_resources(adev, &resource_list,
-				     acpi_i2c_add_resource, &info);
+				     acpi_i2c_add_resource, &rcs_info);
 	acpi_dev_free_resource_list(&resource_list);
 
-	if (ret < 0 || !info.addr)
+	if (ret < 0)
 		return AE_OK;
 
 	adev->power.flags.ignore_parent = true;
-	strlcpy(info.type, dev_name(&adev->dev), sizeof(info.type));
-	if (!i2c_new_device(adapter, &info)) {
-		adev->power.flags.ignore_parent = false;
-		dev_err(&adapter->dev,
-			"failed to add I2C device %s from ACPI\n",
-			dev_name(&adev->dev));
+	info.irq = rcs_info.common_irq;
+	for (i = 0; i < rcs_info.count; ++i) {
+		if (!rcs_info.addr[i])
+			continue;
+		info.addr = rcs_info.addr[i];
+		info.flags = rcs_info.flags[i];
+		/* Status quo, when only one address is present */
+		if (rcs_info.count > 1)
+			snprintf(info.type, sizeof(info.type), "%s:%03x",
+						dev_name(&adev->dev),
+						info.addr);
+		else
+			strlcpy(info.type, dev_name(&adev->dev),
+							sizeof(info.type));
+		i2c_client = i2c_new_device(adapter, &info);
+		if (!i2c_client) {
+			if (!i)
+				adev->power.flags.ignore_parent = false;
+			dev_err(&adapter->dev,
+				"failed to add I2C device %s from ACPI\n",
+					dev_name(&adev->dev));
+			break;
+		}
 	}
 
 	return AE_OK;
@@ -1168,6 +1210,45 @@ static void acpi_i2c_register_devices(struct i2c_adapter *adap)
 	if (ACPI_FAILURE(status))
 		dev_warn(&adap->dev, "failed to enumerate I2C slaves\n");
 }
+
+/* Helper functions to get companion addresses */
+struct acpi_comp_arg {
+	struct acpi_device *acpi_dev;
+	void (*callback)(struct i2c_client *);
+};
+
+static int i2c_acpi_companion(struct device *dev, void *_arg)
+{
+	struct acpi_comp_arg *arg = _arg;
+
+	if (arg->acpi_dev == ACPI_COMPANION(dev)) {
+		struct i2c_client *client;
+
+		client = to_i2c_client(dev);
+		arg->callback(client);
+	}
+
+	return 0;
+}
+
+int i2c_for_each_acpi_comp_client(struct i2c_client *client,
+					void (*callback)(struct i2c_client *))
+{
+	struct acpi_comp_arg arg;
+	int found;
+
+	if (!client)
+		return -EINVAL;
+
+	arg.acpi_dev = ACPI_COMPANION(&client->dev);
+	arg.callback = callback;
+	found = device_for_each_child(&client->adapter->dev, &arg,
+							i2c_acpi_companion);
+
+	return found;
+}
+EXPORT_SYMBOL_GPL(i2c_for_each_acpi_comp_client);
+
 #else
 static inline void acpi_i2c_register_devices(struct i2c_adapter *adap) {}
 #endif /* CONFIG_ACPI */
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index deddeb8..ce75c73 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -323,6 +323,19 @@ extern struct i2c_client *
 i2c_new_dummy(struct i2c_adapter *adap, u16 address);
 
 extern void i2c_unregister_device(struct i2c_client *);
+
+#if IS_ENABLED(CONFIG_ACPI)
+/* Callback to get i2c_client instance for ACPI i2 resource */
+int i2c_for_each_acpi_comp_client(struct i2c_client *client,
+					void (*callback)(struct i2c_client *));
+#else
+int i2c_for_each_acpi_comp_client(struct i2c_client *client,
+					int (*callback)(struct i2c_client *))
+{
+	return 0;
+}
+#endif
+
 #endif /* I2C */
 
 /* Mainboard arch_initcall() code should register all its I2C devices.
-- 
1.7.11.7

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