Leaving the mux enabled causes needless I2C traffic on the downstream
bus. De-selecting after every request causes excess I2C traffic and
switching.
This patch implements a hybrid solution: After 200ms of inactivity,
the mux is disabled.
Signed-off-by: Mike Looijmans <mike.looijm...@topic.nl>
---
drivers/i2c/muxes/i2c-mux-pca954x.c | 45 ++++++++++++++++++++++++++++++++---
1 file changed, 42 insertions(+), 3 deletions(-)
diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c
b/drivers/i2c/muxes/i2c-mux-pca954x.c
index a531d80..1241c97 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -41,6 +41,7 @@
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
+#include <linux/workqueue.h>
#include <linux/i2c/pca954x.h>
@@ -60,7 +61,8 @@ enum pca_type {
struct pca954x {
enum pca_type type;
struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
-
+ struct i2c_client *client;
+ struct delayed_work deselect_work;
u8 last_chan; /* last register value */
};
@@ -168,11 +170,43 @@ static int pca954x_select_chan(struct i2c_adapter *adap,
return ret;
}
-static int pca954x_deselect_mux(struct i2c_adapter *adap,
+static void pca954x_deselect_work(struct work_struct *work)
+{
+ struct pca954x *data = container_of(
+ work, struct pca954x, deselect_work.work);
+ /* Use the adapter lock as a mutex because any method that changes
+ * the mux state will also hold this mutex. If the bus is in use,
+ * the lock will assure that at least that transaction will
+ * complete. */
+ i2c_lock_adapter(data->client->adapter);
+ if (data->last_chan != 0) {
+ int res;
+ /* Disable mux */
+ dev_dbg(&client->dev, "deselecting mux\n");
+ data->last_chan = 0;
+ res = pca954x_reg_write(data->client->adapter,
+ data->client, data->last_chan);
+ if (res < 0)
+ dev_err(&client->dev,
+ "%s: pca954x_reg_write failed: %d\n",
+ __func__, res);
+ }
+ i2c_unlock_adapter(data->client->adapter);
+}
+
+static int pca954x_deselect_mux_delayed(struct i2c_adapter *adap,
void *client, u32 chan)
{
struct pca954x *data = i2c_get_clientdata(client);
+ /* Setup timer to disable at a later interval */
+ schedule_delayed_work(&data->deselect_work, msecs_to_jiffies(200));
+ return 0;
+}
+static int pca954x_deselect_mux_immediate(struct i2c_adapter *adap,
+ void *client, u32 chan)
+{
+ struct pca954x *data = i2c_get_clientdata(client);
/* Deselect active channel */
data->last_chan = 0;
return pca954x_reg_write(adap, client, data->last_chan);
@@ -212,6 +246,8 @@ static int pca954x_probe(struct i2c_client *client,
data->type = id->driver_data;
data->last_chan = 0; /* force the first selection */
+ data->client = client;
+ INIT_DELAYED_WORK(&data->deselect_work, pca954x_deselect_work);
/* Now create an adapter for each channel */
for (num = 0; num < chips[data->type].nchans; num++) {
@@ -231,7 +267,8 @@ static int pca954x_probe(struct i2c_client *client,
i2c_add_mux_adapter(adap, &client->dev, client,
force, num, class, pca954x_select_chan,
(pdata && pdata->modes[num].deselect_on_exit)
- ? pca954x_deselect_mux : NULL);
+ ? pca954x_deselect_mux_immediate
+ : pca954x_deselect_mux_delayed);
if (data->virt_adaps[num] == NULL) {
ret = -ENODEV;
@@ -264,6 +301,8 @@ static int pca954x_remove(struct i2c_client *client)
const struct chip_desc *chip = &chips[data->type];
int i;
+ cancel_delayed_work_sync(&data->deselect_work);
+
for (i = 0; i < chip->nchans; ++i)
if (data->virt_adaps[i]) {
i2c_del_mux_adapter(data->virt_adaps[i]);
--
1.7.9.5
--
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