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Message-ID: <318b22c7-4e90-4055-a893-bb995c16e8da@cherry.de>
Date: Thu, 2 May 2024 17:01:58 +0200
From: Farouk Bouabid <farouk.bouabid@...rry.de>
To: Peter Rosin <peda@...ntia.se>,
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 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)
"""
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
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