From a16d6ebca6efb73f6402f36e5aebf84f61721856 Mon Sep 17 00:00:00 2001 From: Wolfram Sang Date: Sun, 3 Apr 2016 20:44:45 +0200 Subject: i2c: introduce helper function to get 8 bit address from a message Drivers do this in various ways, let's use one standard way of doing it. Note: I2C_M_RD is bit 0, so the code could be simplified. To be extremly robust and to advertise good coding practices, I still use the ternary operator and let the compilers do the optimizing job. Reviewed-by: Andy Shevchenko Signed-off-by: Wolfram Sang --- include/linux/i2c.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/i2c.h') diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 200cf13b00f6..c30833b7b073 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -654,6 +654,11 @@ static inline int i2c_adapter_id(struct i2c_adapter *adap) return adap->nr; } +static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg) +{ + return (msg->addr << 1) | (msg->flags & I2C_M_RD ? 1 : 0); +} + /** * module_i2c_driver() - Helper macro for registering a modular I2C driver * @__i2c_driver: i2c_driver struct -- cgit v1.2.3 From 8320f495cf441d593f7cd4f30e6b63455be71a2c Mon Sep 17 00:00:00 2001 From: Peter Rosin Date: Wed, 4 May 2016 22:15:27 +0200 Subject: i2c: allow adapter drivers to override the adapter locking Add i2c_lock_bus() and i2c_unlock_bus(), which call the new lock_bus and unlock_bus ops in the adapter. These funcs/ops take an additional flags argument that indicates for what purpose the adapter is locked. There are two flags, I2C_LOCK_ROOT_ADAPTER and I2C_LOCK_SEGMENT, but they are both implemented the same. For now. Locking the root adapter means that the whole bus is locked, locking the segment means that only the current bus segment is locked (i.e. i2c traffic on the parent side of a mux is still allowed even if the child side of the mux is locked). Also support a trylock_bus op (but no function to call it, as it is not expected to be needed outside of the i2c core). Implement i2c_lock_adapter/i2c_unlock_adapter in terms of the new locking scheme (i.e. lock with the I2C_LOCK_ROOT_ADAPTER flag). Locking the root adapter and locking the segment is the same thing for all root adapters (e.g. in the normal case of a simple topology with no i2c muxes). The two locking variants are also the same for traditional muxes (aka parent-locked muxes). These muxes traverse the tree, locking each level as they go until they reach the root. This patch is preparatory for a later patch in the series introducing mux-locked muxes, which behave differently depending on the requested locking. Since all current users are using i2c_lock_adapter, which is a wrapper for I2C_LOCK_ROOT_ADAPTER, we only need to annotate the calls that will not need to lock the root adapter for mux-locked muxes. I.e. the instances that needs to use I2C_LOCK_SEGMENT instead of i2c_lock_adapter/I2C_LOCK_ROOT_ADAPTER. Those instances are in the i2c_transfer and i2c_smbus_xfer functions, so that mux-locked muxes can single out normal i2c accesses to its slave side and adjust the locking for those accesses. Signed-off-by: Peter Rosin Signed-off-by: Wolfram Sang --- include/linux/i2c.h | 44 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 42 insertions(+), 2 deletions(-) (limited to 'include/linux/i2c.h') diff --git a/include/linux/i2c.h b/include/linux/i2c.h index c30833b7b073..50934d6e1050 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -538,6 +538,10 @@ struct i2c_adapter { struct i2c_bus_recovery_info *bus_recovery_info; const struct i2c_adapter_quirks *quirks; + + void (*lock_bus)(struct i2c_adapter *, unsigned int flags); + int (*trylock_bus)(struct i2c_adapter *, unsigned int flags); + void (*unlock_bus)(struct i2c_adapter *, unsigned int flags); }; #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev) @@ -567,8 +571,44 @@ i2c_parent_is_i2c_adapter(const struct i2c_adapter *adapter) int i2c_for_each_dev(void *data, int (*fn)(struct device *, void *)); /* Adapter locking functions, exported for shared pin cases */ -void i2c_lock_adapter(struct i2c_adapter *); -void i2c_unlock_adapter(struct i2c_adapter *); +#define I2C_LOCK_ROOT_ADAPTER BIT(0) +#define I2C_LOCK_SEGMENT BIT(1) + +/** + * i2c_lock_bus - Get exclusive access to an I2C bus segment + * @adapter: Target I2C bus segment + * @flags: I2C_LOCK_ROOT_ADAPTER locks the root i2c adapter, I2C_LOCK_SEGMENT + * locks only this branch in the adapter tree + */ +static inline void +i2c_lock_bus(struct i2c_adapter *adapter, unsigned int flags) +{ + adapter->lock_bus(adapter, flags); +} + +/** + * i2c_unlock_bus - Release exclusive access to an I2C bus segment + * @adapter: Target I2C bus segment + * @flags: I2C_LOCK_ROOT_ADAPTER unlocks the root i2c adapter, I2C_LOCK_SEGMENT + * unlocks only this branch in the adapter tree + */ +static inline void +i2c_unlock_bus(struct i2c_adapter *adapter, unsigned int flags) +{ + adapter->unlock_bus(adapter, flags); +} + +static inline void +i2c_lock_adapter(struct i2c_adapter *adapter) +{ + i2c_lock_bus(adapter, I2C_LOCK_ROOT_ADAPTER); +} + +static inline void +i2c_unlock_adapter(struct i2c_adapter *adapter) +{ + i2c_unlock_bus(adapter, I2C_LOCK_ROOT_ADAPTER); +} /*flags for the client struct: */ #define I2C_CLIENT_PEC 0x04 /* Use Packet Error Checking */ -- cgit v1.2.3 From 6ef91fcca8a8ba3df9810a4cc6cd6a9d3f21bf45 Mon Sep 17 00:00:00 2001 From: Peter Rosin Date: Wed, 4 May 2016 22:15:29 +0200 Subject: i2c: mux: relax locking of the top i2c adapter during mux-locked muxing With a i2c topology like the following GPIO ---| ------ BAT1 | v / I2C -----+----------+---- MUX | \ EEPROM ------ BAT2 there is a locking problem with the GPIO controller since it is a client on the same i2c bus that it muxes. Transfers to the mux clients (e.g. BAT1) will lock the whole i2c bus prior to attempting to switch the mux to the correct i2c segment. In the above case, the GPIO device is an I/O expander with an i2c interface, and since the GPIO subsystem knows nothing (and rightfully so) about the lockless needs of the i2c mux code, this results in a deadlock when the GPIO driver issues i2c transfers to modify the mux. So, observing that while it is needed to have the i2c bus locked during the actual MUX update in order to avoid random garbage on the slave side, it is not strictly a must to have it locked over the whole sequence of a full select-transfer-deselect mux client operation. The mux itself needs to be locked, so transfers to clients behind the mux are serialized, and the mux needs to be stable during all i2c traffic (otherwise individual mux slave segments might see garbage, or worse). Introduce this new locking concept as "mux-locked" muxes, and call the pre-existing mux locking scheme "parent-locked". Modify the i2c mux locking so that muxes that are "mux-locked" locks only the muxes on the parent adapter instead of the whole i2c bus when there is a transfer to the slave side of the mux. This lock serializes transfers to the slave side of the muxes on the parent adapter. Add code to i2c-mux-gpio and i2c-mux-pinctrl that checks if all involved gpio/pinctrl devices have a parent that is an i2c adapter in the same adapter tree that is muxed, and request a "mux-locked mux" if that is the case. Modify the select-transfer-deselect code for "mux-locked" muxes so that each of the select-transfer-deselect ops locks the mux parent adapter individually. Signed-off-by: Peter Rosin Signed-off-by: Wolfram Sang --- include/linux/i2c.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/i2c.h') diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 50934d6e1050..96a25ae14494 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -524,6 +524,7 @@ struct i2c_adapter { /* data fields that are valid for all devices */ struct rt_mutex bus_lock; + struct rt_mutex mux_lock; int timeout; /* in jiffies */ int retries; -- cgit v1.2.3