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Message-ID: <9b12dc9f-054b-fba5-e23d-48d0fe1a00e2@axentia.se>
Date: Mon, 6 May 2024 23:26:37 +0200
From: Peter Rosin <peda@...ntia.se>
To: Farouk Bouabid <farouk.bouabid@...rry.de>,
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@...rry.de>, Heiko Stuebner <heiko@...ech.de>,
Quentin Schulz <quentin.schulz@...obroma-systems.com>
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 v2 1/7] i2c: mux: add the ability to share mux core
address with child nodes
Hi!
Regarding the subject (and elsewhere) I think of "mux core" as roughly
the code in the i2c-mux.c file. So, for me, the "mux core" does not have
an address, it is a mux "driver instance" or "device" that sits on the
I2C address that you need to share.
2024-05-06 at 13:37, Farouk Bouabid wrote:
> Allow the mux core (if it's an i2c device) to have the same address as
> a child device. This is useful when the mux core can only use an i2c
> address that is used by a child device because no other addresses are
> free to use. eg. the mux core can only use address 0x18 which is used by
> amc6821 connected to the mux.
Use I2C in text, not i2c (applies to other patches as well).
>
> Signed-off-by: Farouk Bouabid <farouk.bouabid@...rry.de>
> ---
> drivers/i2c/i2c-core-base.c | 6 +++++-
> drivers/i2c/i2c-mux.c | 25 ++++++++++++++++++++++++-
> include/linux/i2c-mux.h | 1 +
> include/linux/i2c.h | 7 +++++++
> 4 files changed, 37 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index ff5c486a1dbb..ce2425b0486d 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -821,9 +821,13 @@ 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 && adapter->quirks->flags & I2C_AQ_SKIP_ADDR_CHECK)
> + skip_check = adapter->quirks->skip_addr_in_parent == addr;
> +
> + 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..bdb75a130cab 100644
> --- a/drivers/i2c/i2c-mux.c
> +++ b/drivers/i2c/i2c-mux.c
> @@ -334,7 +334,30 @@ 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 core 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 && muxc->dev->type == &i2c_client_type) {
> + struct i2c_adapter_quirks *quirks = devm_kzalloc(muxc->dev,
> + sizeof(*quirks), GFP_KERNEL);
> + struct i2c_client *client = to_i2c_client(muxc->dev);
The above section has overly long lines without good reason. Please
rewrite as something like this:
/*
* 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 device 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 &&
muxc->dev->type == &i2c_client_type)
{
struct i2c_client *client = to_i2c_client(muxc->dev);
struct i2c_adapter_quirks *quirks;
quirks = devm_kzalloc(muxc->dev, sizeof(*quirks), GFP_KERNEL);
I also wonder if that second condition (...->type == &i2c_client_type) should
be a WARN_ON_ONCE? I don't see how the flag can be set sanely on an adapter
that is not itself an I2C client. Can it?
> +
> + if (!quirks)
> + return -ENOMEM;
> +
> + if (parent->quirks)
> + memcpy(quirks, parent->quirks, sizeof(*quirks));
> +
> + quirks->flags |= I2C_AQ_SKIP_ADDR_CHECK;
> + quirks->skip_addr_in_parent = client->addr;
> + priv->adap.quirks = quirks;
The I2C_AQ_SKIP_ADDR_CHECK flag should probably not be propagated?
} else if (priv->adap.quirks &&
priv->adap.quirks->flags & I2C_AQ_SKIP_ADDR_CHECK)
{
struct i2c_adapter_quirks *quirks;
quirks = devm_kzalloc(muxc->dev, sizeof(*quirks), GFP_KERNEL);
if (!quirks)
return -ENOMEM;
memcpy(quirks, parent->quirks, sizeof(*quirks));
quirks->flags &= ~I2C_AQ_SKIP_ADDR_CHECK;
priv->adap.quirks = quirks;
(My code written directly in the mua, there's probably something silly in
there...)
Cheers,
Peter
> + } else {
> + priv->adap.quirks = parent->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..c3acbaaadae9 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -670,6 +670,7 @@ int i2c_generic_scl_recovery(struct i2c_adapter *adap);
> * @max_read_len: maximum length of a read message
> * @max_comb_1st_msg_len: maximum length of the first msg in a combined message
> * @max_comb_2nd_msg_len: maximum length of the second msg in a combined message
> + * @skip_addr_in_parent: No conflict check on parent adapter for a given address
> *
> * Note about combined messages: Some I2C controllers can only send one message
> * per transfer, plus something called combined message or write-then-read.
> @@ -690,6 +691,7 @@ struct i2c_adapter_quirks {
> u16 max_read_len;
> u16 max_comb_1st_msg_len;
> u16 max_comb_2nd_msg_len;
> + unsigned short skip_addr_in_parent;
> };
>
> /* enforce max_num_msgs = 2 and use max_comb_*_len for length checks */
> @@ -711,6 +713,11 @@ 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)
> +/**
> + * do not check for conflict on a given address
> + * used accordingly with "struct i2c_adapter_quirks.skip_addr_in_parent"
> + */
> +#define I2C_AQ_SKIP_ADDR_CHECK BIT(8)
>
> /*
> * i2c_adapter is the structure used to identify a physical i2c bus along
>
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