| Message ID | 20240506-dev-mule-i2c-mux-v2-1-a91c954f65d7@cherry.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add Mule I2C multiplexer support | expand |
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@cherry.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 >
Hi Peter, On 5/6/24 11:26 PM, Peter Rosin wrote: > 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. > I'm the one who suggested mux core here (privately) :) The issue is that in my head a mux device is the i2c adapter/bus (from i2c-mux.yaml dt binding example): """ i2c { #address-cells = <1>; #size-cells = <0>; i2c-mux@70 { compatible = "nxp,pca9548"; reg = <0x70>; #address-cells = <1>; #size-cells = <0>; i2c@3 { #address-cells = <1>; #size-cells = <0>; reg = <3>; gpio@20 { compatible = "nxp,pca9555"; gpio-controller; #gpio-cells = <2>; reg = <0x20>; }; }; i2c@4 { #address-cells = <1>; #size-cells = <0>; reg = <4>; gpio@20 { compatible = "nxp,pca9555"; gpio-controller; #gpio-cells = <2>; reg = <0x20>; }; }; }; }; """ "mux core" here would refer to i2c-mux@70, "mux device"/"mux" i2c@3 or i2c@4. E.g. when I'm saying "in mux 3", I'm talking about i2c@3 here. For me a driver instance is a device, so "mux driver instance" would be a "mux device". Ah... naming is hard. Anyway, up to you, I just wanted to make sure we're talking about the same thing and there's no confusion here. [...] > 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? > Agreed, good suggestion here... Though... https://lwn.net/Articles/969923/ it seems new additions of WARN_ON are now discouraged? Not looking to start a discussion here about whether WARN_ON is good or bad, merely pointing at this if it was missed somehow. >> + >> + 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? > Oh... you mean if we have a mux on an i2c adapter of a mux and the adapters handled by the parent mux have SKIP_ADDR set and we don't want the adapters handled by the leaf mux to have this flag as well? Is that what you meant? Cheers, Quentin
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); + + 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; + } 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
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. Signed-off-by: Farouk Bouabid <farouk.bouabid@cherry.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(-)