diff options
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x | 20 | ||||
| -rw-r--r-- | drivers/i2c/muxes/i2c-mux-pca954x.c | 85 |
2 files changed, 97 insertions, 8 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x b/Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x new file mode 100644 index 000000000000..0b0de8cd0d13 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-bus-i2c-devices-pca954x @@ -0,0 +1,20 @@ +What: /sys/bus/i2c/.../idle_state +Date: January 2019 +KernelVersion: 5.2 +Contact: Robert Shearman <robert.shearman@att.com> +Description: + Value that exists only for mux devices that can be + written to control the behaviour of the multiplexer on + idle. Possible values: + -2 - disconnect on idle, i.e. deselect the last used + channel, which is useful when there is a device + with an address that conflicts with another + device on another mux on the same parent bus. + -1 - leave the mux as-is, which is the most optimal + setting in terms of I2C operations and is the + default mode. + 0..<nchans> - set the mux to a predetermined channel, + which is useful if there is one channel that is + used almost always, and you want to reduce the + latency for normal operations after rare + transactions on other channels diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index e32fef560684..923aa3a5a3dc 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -49,6 +49,7 @@ #include <linux/pm.h> #include <linux/slab.h> #include <linux/spinlock.h> +#include <dt-bindings/mux/mux.h> #define PCA954X_MAX_NCHANS 8 @@ -84,7 +85,9 @@ struct pca954x { const struct chip_desc *chip; u8 last_chan; /* last register value */ - u8 deselect; + /* MUX_IDLE_AS_IS, MUX_IDLE_DISCONNECT or >= 0 for channel */ + s8 idle_state; + struct i2c_client *client; struct irq_domain *irq; @@ -253,15 +256,71 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan) { struct pca954x *data = i2c_mux_priv(muxc); struct i2c_client *client = data->client; + s8 idle_state; + + idle_state = READ_ONCE(data->idle_state); + if (idle_state >= 0) + /* Set the mux back to a predetermined channel */ + return pca954x_select_chan(muxc, idle_state); + + if (idle_state == MUX_IDLE_DISCONNECT) { + /* Deselect active channel */ + data->last_chan = 0; + return pca954x_reg_write(muxc->parent, client, + data->last_chan); + } - if (!(data->deselect & (1 << chan))) - return 0; + /* otherwise leave as-is */ - /* Deselect active channel */ - data->last_chan = 0; - return pca954x_reg_write(muxc->parent, client, data->last_chan); + return 0; +} + +static ssize_t idle_state_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct i2c_client *client = to_i2c_client(dev); + struct i2c_mux_core *muxc = i2c_get_clientdata(client); + struct pca954x *data = i2c_mux_priv(muxc); + + return sprintf(buf, "%d\n", READ_ONCE(data->idle_state)); +} + +static ssize_t idle_state_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct i2c_client *client = to_i2c_client(dev); + struct i2c_mux_core *muxc = i2c_get_clientdata(client); + struct pca954x *data = i2c_mux_priv(muxc); + int val; + int ret; + + ret = kstrtoint(buf, 0, &val); + if (ret < 0) + return ret; + + if (val != MUX_IDLE_AS_IS && val != MUX_IDLE_DISCONNECT && + (val < 0 || val >= data->chip->nchans)) + return -EINVAL; + + i2c_lock_bus(muxc->parent, I2C_LOCK_SEGMENT); + + WRITE_ONCE(data->idle_state, val); + /* + * Set the mux into a state consistent with the new + * idle_state. + */ + if (data->last_chan || val != MUX_IDLE_DISCONNECT) + ret = pca954x_deselect_mux(muxc, 0); + + i2c_unlock_bus(muxc->parent, I2C_LOCK_SEGMENT); + + return ret < 0 ? ret : count; } +static DEVICE_ATTR_RW(idle_state); + static irqreturn_t pca954x_irq_handler(int irq, void *dev_id) { struct pca954x *data = dev_id; @@ -328,8 +387,11 @@ static int pca954x_irq_setup(struct i2c_mux_core *muxc) static void pca954x_cleanup(struct i2c_mux_core *muxc) { struct pca954x *data = i2c_mux_priv(muxc); + struct i2c_client *client = data->client; int c, irq; + device_remove_file(&client->dev, &dev_attr_idle_state); + if (data->irq) { for (c = 0; c < data->chip->nchans; c++) { irq = irq_find_mapping(data->irq, c); @@ -410,9 +472,12 @@ static int pca954x_probe(struct i2c_client *client, } data->last_chan = 0; /* force the first selection */ + data->idle_state = MUX_IDLE_AS_IS; idle_disconnect_dt = np && of_property_read_bool(np, "i2c-mux-idle-disconnect"); + if (idle_disconnect_dt) + data->idle_state = MUX_IDLE_DISCONNECT; ret = pca954x_irq_setup(muxc); if (ret) @@ -420,8 +485,6 @@ static int pca954x_probe(struct i2c_client *client, /* Now create an adapter for each channel */ for (num = 0; num < data->chip->nchans; num++) { - data->deselect |= idle_disconnect_dt << num; - ret = i2c_mux_add_adapter(muxc, 0, num, 0); if (ret) goto fail_cleanup; @@ -436,6 +499,12 @@ static int pca954x_probe(struct i2c_client *client, goto fail_cleanup; } + /* + * The attr probably isn't going to be needed in most cases, + * so don't fail completely on error. + */ + device_create_file(dev, &dev_attr_idle_state); + dev_info(dev, "registered %d multiplexed busses for I2C %s %s\n", num, data->chip->muxtype == pca954x_ismux ? "mux" : "switch", client->name); |