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Message-ID: <c5e375a0-8c64-f244-a5e6-bfcb3400d05a@axentia.se>
Date: Fri, 3 May 2024 07:30:07 +0200
From: Peter Rosin <peda@...ntia.se>
To: Farouk Bouabid <farouk.bouabid@...rry.de>,
Farouk Bouabid <farouk.bouabid@...obroma-systems.com>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>,
Quentin Schulz <quentin.schulz@...obroma-systems.com>,
Heiko Stuebner <heiko@...ech.de>
Cc: linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH 1/7] i2c: mux: add the ability to share mux-address with
child nodes
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@...obroma-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
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