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Date: Tue, 10 Jun 2014 08:09:22 -0700
From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
CC: wsa@...-dreams.de, linux-kernel@...r.kernel.org,
linux-i2c@...r.kernel.org
Subject: Re: [PATCH 1/2] i2c/ACPI: Support for multiple serial bus addresses
On 06/10/2014 02:24 AM, Mika Westerberg wrote:
> On Thu, Apr 10, 2014 at 09:15:16PM -0700, Srinivas Pandruvada wrote:
>> 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.
>
> How does the client driver see this?
>
> If I have a device that has multiple addresses but it is the same
> physical device, how does the driver deal with it? For example how
> drivers/misc/eeprom/at24.c could take advantage of this?
>
Use i2c_for_each_acpi_comp_client. I use similar approach as
i2c_for_each_dev already defined in i2c.h.
> I also think that this needs to documented somewhere under
> Documentation/i2c/* or so.
>
>> 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@...ux.intel.com>
>> ---
>> 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) {
>
> Instead of this, would it make sense if you do the device creation in
> acpi_i2c_add_resource() for each enumerated device?
>
You can't. Because the interrupt resource is common. You may see that
definition (as above examples), you have to go through the list before,
to find out irq number, which is needed to create i2c device, if there
is any IRQ.
> At least it would look better than this ;-)
>
>> + 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;
>> +}
>> +
>
> Missing kernel doc here.
>
>> +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);
>
> Since devices with multiple addresses seem to exist in real world, I
> think it would be beneficial to add a bit more generic implementation of
> the above to the I2C core instead. Then non-ACPI systems could also take
> advantage of it.
>
What is your suggestion? i2c already use similar method for finding each
i2c_for_each_dev, I felt similar method would be sufficient.
>> +
>> #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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>
Thanks,
Srinivas
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