diff mbox series

[1/7] i2c: mux: add the ability to share mux-address with child nodes

Message ID 20240426-dev-mule-i2c-mux-v1-1-045a482f6ffb@theobroma-systems.com
State New
Headers show
Series Add Mule I2C multiplexer support | expand

Commit Message

Farouk Bouabid April 26, 2024, 4:49 p.m. UTC
Allow the mux to have the same address as a child device. This is useful
when the mux can only use an i2c-address that is used by a child device
because no other addresses are free to use. eg. the mux can only use
address 0x18 which is used by amc6821 connected to the mux.

Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com>
---
 drivers/i2c/i2c-mux.c   | 10 +++++++++-
 include/linux/i2c-mux.h |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

Comments

Farouk Bouabid May 2, 2024, 3:01 p.m. UTC | #1
Hi Peter,

On 29.04.24 17:46, Peter Rosin wrote:
> Hi!
>
> 2024-04-26 at 18:49, Farouk Bouabid wrote:
>> Allow the mux to have the same address as a child device. This is useful
>> when the mux can only use an i2c-address that is used by a child device
>> because no other addresses are free to use. eg. the mux can only use
>> address 0x18 which is used by amc6821 connected to the mux.
>>
>> Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com>
>> ---
>>   drivers/i2c/i2c-mux.c   | 10 +++++++++-
>>   include/linux/i2c-mux.h |  1 +
>>   2 files changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
>> index 57ff09f18c37..f5357dff8cc5 100644
>> --- a/drivers/i2c/i2c-mux.c
>> +++ b/drivers/i2c/i2c-mux.c
>> @@ -331,7 +331,6 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>>   	priv->adap.owner = THIS_MODULE;
>>   	priv->adap.algo = &priv->algo;
>>   	priv->adap.algo_data = priv;
>> -	priv->adap.dev.parent = &parent->dev;
>>   	priv->adap.retries = parent->retries;
>>   	priv->adap.timeout = parent->timeout;
>>   	priv->adap.quirks = parent->quirks;
>> @@ -348,6 +347,15 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>>   	else
>>   		priv->adap.class = class;
>>   
>> +	/*
>> +	 * When creating the adapter, the node devices are checked for i2c address
>> +	 * match with other devices on the parent adapter, among which is the mux itself.
>> +	 * If a match is found the node device is not probed successfully.
>> +	 * Allow the mux to have the same address as a child device by skipping this check.
>> +	 */
>> +	if (!(muxc->share_addr_with_children))
>> +		priv->adap.dev.parent = &parent->dev;
> This is a dirty hack that will not generally do the right thing.
>
> The adapter device parent is not there solely for the purpose of
> detecting address clashes, so the above has other implications
> that are not desirable.
>
> Therefore, NACK on this approach. It simply needs to be more involved.
> Sorry.
>
> Cheers,
> Peter
>

Another way to approach this is by implementing this flag as a quirk for 
the added adapter:

(tested but not cleaned up)

"""

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index ff5c486a1dbb..6a0237f750db 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -821,9 +821,21 @@ static int i2c_check_mux_children(struct device 
*dev, void *addrp)
  static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
  {
         struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
+       bool skip_check = false;
         int result = 0;

-       if (parent)
+       if (adapter->quirks) {
+                if (adapter->quirks->flags & I2C_AQ_SHARE_ADDR) {
+                       struct i2c_client *client = 
of_find_i2c_device_by_node(adapter->dev.of_node->parent);
+
+                       if (client) {
+                               skip_check = client->addr == addr;
+                               put_device(&client->dev);
+                       }
+                }
+       }
+
+       if (parent && !skip_check)
                 result = i2c_check_mux_parents(parent, addr);

         if (!result)
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 57ff09f18c37..e87cb0e43725 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -334,7 +334,26 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
         priv->adap.dev.parent = &parent->dev;
         priv->adap.retries = parent->retries;
         priv->adap.timeout = parent->timeout;
-       priv->adap.quirks = parent->quirks;
+       /*
+        * When creating the adapter, the node devices are checked for 
i2c address
+        * match with other devices on the parent adapter, among which 
is the mux itself.
+        * If a match is found the node device is not probed successfully.
+        * Allow the mux to have the same address as a child device by 
skipping this check.
+        */
+       if (!muxc->share_addr_with_children)
+               priv->adap.quirks = parent->quirks;
+       else {
+               struct i2c_adapter_quirks *quirks = 
kzalloc(sizeof(*quirks), GFP_KERNEL);
+               if (!quirks)
+                       return -ENOMEM;
+
+               if (parent->quirks)
+                       *quirks = *(parent->quirks); // @fixme memcpy
+
+               quirks->flags |= I2C_AQ_SHARE_ADDR;
+               priv->adap.quirks = quirks;
+       }
+
         if (muxc->mux_locked)
                 priv->adap.lock_ops = &i2c_mux_lock_ops;
         else
diff --git a/include/linux/i2c-mux.h b/include/linux/i2c-mux.h
index 98ef73b7c8fd..17ac68bf1703 100644
--- a/include/linux/i2c-mux.h
+++ b/include/linux/i2c-mux.h
@@ -21,6 +21,7 @@ struct i2c_mux_core {
         unsigned int mux_locked:1;
         unsigned int arbitrator:1;
         unsigned int gate:1;
+       unsigned int share_addr_with_children:1;

         void *priv;

diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 5e6cd43a6dbd..2ebac9e672ef 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -711,6 +711,8 @@ struct i2c_adapter_quirks {
  #define I2C_AQ_NO_ZERO_LEN             (I2C_AQ_NO_ZERO_LEN_READ | 
I2C_AQ_NO_ZERO_LEN_WRITE)
  /* adapter cannot do repeated START */
  #define I2C_AQ_NO_REP_START            BIT(7)
+/* @fixme document and find proper name */
+#define I2C_AQ_SHARE_ADDR              BIT(8)

  /*
   * i2c_adapter is the structure used to identify a physical i2c bus along

"""

This works, however this only supports device-tree because of 
of_find_i2c_device_by_node. If we want to support acpi then we can either:


1. Get the Mule i2c device address from fwnode_get_next_parent_dev but 
this is static since v6.9-rcx.

2. Pass the Mule i2c device address as a new member of  struct 
i2c_adapter_quirks.


I would go for 2. Do you suggest something else?

Best regards

Farouk
Peter Rosin May 3, 2024, 5:30 a.m. UTC | #2
Hi!

2024-05-02 at 17:01, Farouk Bouabid wrote:
> Hi Peter,
> 
> On 29.04.24 17:46, Peter Rosin wrote:
>> Hi!
>>
>> 2024-04-26 at 18:49, Farouk Bouabid wrote:
>>> Allow the mux to have the same address as a child device. This is useful
>>> when the mux can only use an i2c-address that is used by a child device
>>> because no other addresses are free to use. eg. the mux can only use
>>> address 0x18 which is used by amc6821 connected to the mux.
>>>
>>> Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com>
>>> ---
>>>   drivers/i2c/i2c-mux.c   | 10 +++++++++-
>>>   include/linux/i2c-mux.h |  1 +
>>>   2 files changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
>>> index 57ff09f18c37..f5357dff8cc5 100644
>>> --- a/drivers/i2c/i2c-mux.c
>>> +++ b/drivers/i2c/i2c-mux.c
>>> @@ -331,7 +331,6 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>>>       priv->adap.owner = THIS_MODULE;
>>>       priv->adap.algo = &priv->algo;
>>>       priv->adap.algo_data = priv;
>>> -    priv->adap.dev.parent = &parent->dev;
>>>       priv->adap.retries = parent->retries;
>>>       priv->adap.timeout = parent->timeout;
>>>       priv->adap.quirks = parent->quirks;
>>> @@ -348,6 +347,15 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>>>       else
>>>           priv->adap.class = class;
>>>   +    /*
>>> +     * When creating the adapter, the node devices are checked for i2c address
>>> +     * match with other devices on the parent adapter, among which is the mux itself.
>>> +     * If a match is found the node device is not probed successfully.
>>> +     * Allow the mux to have the same address as a child device by skipping this check.
>>> +     */
>>> +    if (!(muxc->share_addr_with_children))
>>> +        priv->adap.dev.parent = &parent->dev;
>> This is a dirty hack that will not generally do the right thing.
>>
>> The adapter device parent is not there solely for the purpose of
>> detecting address clashes, so the above has other implications
>> that are not desirable.
>>
>> Therefore, NACK on this approach. It simply needs to be more involved.
>> Sorry.
>>
>> Cheers,
>> Peter
>>
> 
> Another way to approach this is by implementing this flag as a quirk for the added adapter:
> 
> (tested but not cleaned up)

Yes, good idea, this is much more targeted and generally feels a lot
better.

> 
> """
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index ff5c486a1dbb..6a0237f750db 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -821,9 +821,21 @@ static int i2c_check_mux_children(struct device *dev, void *addrp)
>  static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
>  {
>         struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
> +       bool skip_check = false;
>         int result = 0;
> 
> -       if (parent)
> +       if (adapter->quirks) {
> +                if (adapter->quirks->flags & I2C_AQ_SHARE_ADDR) {
> +                       struct i2c_client *client = of_find_i2c_device_by_node(adapter->dev.of_node->parent);
> +
> +                       if (client) {
> +                               skip_check = client->addr == addr;
> +                               put_device(&client->dev);
> +                       }
> +                }
> +       }
> +
> +       if (parent && !skip_check)
>                 result = i2c_check_mux_parents(parent, addr);
> 
>         if (!result)
> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
> index 57ff09f18c37..e87cb0e43725 100644
> --- a/drivers/i2c/i2c-mux.c
> +++ b/drivers/i2c/i2c-mux.c
> @@ -334,7 +334,26 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>         priv->adap.dev.parent = &parent->dev;
>         priv->adap.retries = parent->retries;
>         priv->adap.timeout = parent->timeout;
> -       priv->adap.quirks = parent->quirks;
> +       /*
> +        * When creating the adapter, the node devices are checked for i2c address
> +        * match with other devices on the parent adapter, among which is the mux itself.
> +        * If a match is found the node device is not probed successfully.
> +        * Allow the mux to have the same address as a child device by skipping this check.
> +        */
> +       if (!muxc->share_addr_with_children)
> +               priv->adap.quirks = parent->quirks;
> +       else {
> +               struct i2c_adapter_quirks *quirks = kzalloc(sizeof(*quirks), GFP_KERNEL);

This leaks, dev_kzalloc?

> +               if (!quirks)
> +                       return -ENOMEM;
> +
> +               if (parent->quirks)
> +                       *quirks = *(parent->quirks); // @fixme memcpy
> +
> +               quirks->flags |= I2C_AQ_SHARE_ADDR;
> +               priv->adap.quirks = quirks;
> +       }
> +
>         if (muxc->mux_locked)
>                 priv->adap.lock_ops = &i2c_mux_lock_ops;
>         else
> diff --git a/include/linux/i2c-mux.h b/include/linux/i2c-mux.h
> index 98ef73b7c8fd..17ac68bf1703 100644
> --- a/include/linux/i2c-mux.h
> +++ b/include/linux/i2c-mux.h
> @@ -21,6 +21,7 @@ struct i2c_mux_core {
>         unsigned int mux_locked:1;
>         unsigned int arbitrator:1;
>         unsigned int gate:1;
> +       unsigned int share_addr_with_children:1;
> 
>         void *priv;
> 
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 5e6cd43a6dbd..2ebac9e672ef 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -711,6 +711,8 @@ struct i2c_adapter_quirks {
>  #define I2C_AQ_NO_ZERO_LEN             (I2C_AQ_NO_ZERO_LEN_READ | I2C_AQ_NO_ZERO_LEN_WRITE)
>  /* adapter cannot do repeated START */
>  #define I2C_AQ_NO_REP_START            BIT(7)
> +/* @fixme document and find proper name */
> +#define I2C_AQ_SHARE_ADDR              BIT(8)
> 
>  /*
>   * i2c_adapter is the structure used to identify a physical i2c bus along
> 
> """
> 
> This works, however this only supports device-tree because of of_find_i2c_device_by_node. If we want to support acpi then we can either:
> 
> 
> 1. Get the Mule i2c device address from fwnode_get_next_parent_dev but this is static since v6.9-rcx.
> 
> 2. Pass the Mule i2c device address as a new member of  struct i2c_adapter_quirks.
> 
> 
> I would go for 2. Do you suggest something else?

Yes, 2 is definitely neater.

Thanks!

Cheers,
Peter
Quentin Schulz May 3, 2024, 4:20 p.m. UTC | #3
Hi Peter,

On 5/3/24 7:30 AM, Peter Rosin wrote:
> Hi!
> 
> 2024-05-02 at 17:01, Farouk Bouabid wrote:
>> Hi Peter,
>>
>> On 29.04.24 17:46, Peter Rosin wrote:
>>> Hi!
>>>
>>> 2024-04-26 at 18:49, Farouk Bouabid wrote:
>>>> Allow the mux to have the same address as a child device. This is useful
>>>> when the mux can only use an i2c-address that is used by a child device
>>>> because no other addresses are free to use. eg. the mux can only use
>>>> address 0x18 which is used by amc6821 connected to the mux.
>>>>
>>>> Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-systems.com>
>>>> ---
>>>>    drivers/i2c/i2c-mux.c   | 10 +++++++++-
>>>>    include/linux/i2c-mux.h |  1 +
>>>>    2 files changed, 10 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
>>>> index 57ff09f18c37..f5357dff8cc5 100644
>>>> --- a/drivers/i2c/i2c-mux.c
>>>> +++ b/drivers/i2c/i2c-mux.c
>>>> @@ -331,7 +331,6 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>>>>        priv->adap.owner = THIS_MODULE;
>>>>        priv->adap.algo = &priv->algo;
>>>>        priv->adap.algo_data = priv;
>>>> -    priv->adap.dev.parent = &parent->dev;
>>>>        priv->adap.retries = parent->retries;
>>>>        priv->adap.timeout = parent->timeout;
>>>>        priv->adap.quirks = parent->quirks;
>>>> @@ -348,6 +347,15 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>>>>        else
>>>>            priv->adap.class = class;
>>>>    +    /*
>>>> +     * When creating the adapter, the node devices are checked for i2c address
>>>> +     * match with other devices on the parent adapter, among which is the mux itself.
>>>> +     * If a match is found the node device is not probed successfully.
>>>> +     * Allow the mux to have the same address as a child device by skipping this check.
>>>> +     */
>>>> +    if (!(muxc->share_addr_with_children))
>>>> +        priv->adap.dev.parent = &parent->dev;
>>> This is a dirty hack that will not generally do the right thing.
>>>
>>> The adapter device parent is not there solely for the purpose of
>>> detecting address clashes, so the above has other implications
>>> that are not desirable.
>>>
>>> Therefore, NACK on this approach. It simply needs to be more involved.
>>> Sorry.
>>>
>>> Cheers,
>>> Peter
>>>
>>
>> Another way to approach this is by implementing this flag as a quirk for the added adapter:
>>
>> (tested but not cleaned up)
> 
> Yes, good idea, this is much more targeted and generally feels a lot
> better.
> 
>>
>> """
>>
>> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
>> index ff5c486a1dbb..6a0237f750db 100644
>> --- a/drivers/i2c/i2c-core-base.c
>> +++ b/drivers/i2c/i2c-core-base.c
>> @@ -821,9 +821,21 @@ static int i2c_check_mux_children(struct device *dev, void *addrp)
>>   static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
>>   {
>>          struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
>> +       bool skip_check = false;
>>          int result = 0;
>>
>> -       if (parent)
>> +       if (adapter->quirks) {
>> +                if (adapter->quirks->flags & I2C_AQ_SHARE_ADDR) {
>> +                       struct i2c_client *client = of_find_i2c_device_by_node(adapter->dev.of_node->parent);
>> +
>> +                       if (client) {
>> +                               skip_check = client->addr == addr;
>> +                               put_device(&client->dev);
>> +                       }
>> +                }
>> +       }
>> +
>> +       if (parent && !skip_check)
>>                  result = i2c_check_mux_parents(parent, addr);
>>
>>          if (!result)
>> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
>> index 57ff09f18c37..e87cb0e43725 100644
>> --- a/drivers/i2c/i2c-mux.c
>> +++ b/drivers/i2c/i2c-mux.c
>> @@ -334,7 +334,26 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
>>          priv->adap.dev.parent = &parent->dev;
>>          priv->adap.retries = parent->retries;
>>          priv->adap.timeout = parent->timeout;
>> -       priv->adap.quirks = parent->quirks;
>> +       /*
>> +        * When creating the adapter, the node devices are checked for i2c address
>> +        * match with other devices on the parent adapter, among which is the mux itself.
>> +        * If a match is found the node device is not probed successfully.
>> +        * Allow the mux to have the same address as a child device by skipping this check.
>> +        */
>> +       if (!muxc->share_addr_with_children)
>> +               priv->adap.quirks = parent->quirks;
>> +       else {
>> +               struct i2c_adapter_quirks *quirks = kzalloc(sizeof(*quirks), GFP_KERNEL);
> 
> This leaks, dev_kzalloc?
> 

Quick questions about this though.

priv is allocated with kzalloc and not devm_kzalloc and is then manually 
kfree'd either as part of the error path or in i2c_del_mux_adapters. Is 
there a reason for this? Shouldn't we migrate this to devm allocation as 
well?

Similarly, I was wondering if we couldn't add a devm_add_action_or_reset 
for i2c_del_mux_adapters in i2c_add_mux_adapter? Is there something that 
prevents us from doing this?

Cheers,
Quentin
diff mbox series

Patch

diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 57ff09f18c37..f5357dff8cc5 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -331,7 +331,6 @@  int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 	priv->adap.owner = THIS_MODULE;
 	priv->adap.algo = &priv->algo;
 	priv->adap.algo_data = priv;
-	priv->adap.dev.parent = &parent->dev;
 	priv->adap.retries = parent->retries;
 	priv->adap.timeout = parent->timeout;
 	priv->adap.quirks = parent->quirks;
@@ -348,6 +347,15 @@  int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 	else
 		priv->adap.class = class;
 
+	/*
+	 * When creating the adapter, the node devices are checked for i2c address
+	 * match with other devices on the parent adapter, among which is the mux itself.
+	 * If a match is found the node device is not probed successfully.
+	 * Allow the mux to have the same address as a child device by skipping this check.
+	 */
+	if (!(muxc->share_addr_with_children))
+		priv->adap.dev.parent = &parent->dev;
+
 	/*
 	 * Try to populate the mux adapter's of_node, expands to
 	 * nothing if !CONFIG_OF.
diff --git a/include/linux/i2c-mux.h b/include/linux/i2c-mux.h
index 98ef73b7c8fd..17ac68bf1703 100644
--- a/include/linux/i2c-mux.h
+++ b/include/linux/i2c-mux.h
@@ -21,6 +21,7 @@  struct i2c_mux_core {
 	unsigned int mux_locked:1;
 	unsigned int arbitrator:1;
 	unsigned int gate:1;
+	unsigned int share_addr_with_children:1;
 
 	void *priv;