[v6,2/3] i2c: mux: pca954x: support property idle-state

Biwen Li
2019-11-29T09:22:56Z

This supports property idle-state,if present,
overrides i2c-mux-idle-disconnect.

My use cases:
- Use the property idle-state to fix
an errata on LS2085ARDB and LS2088ARDB.
- Errata id: E-00013(board LS2085ARDB and
LS2088ARDB revision on Rev.B, Rev.C and Rev.D).
- About E-00013:
- Description: I2C1 and I2C3 buses
are missing pull-up.
- Impact: When the PCA954x device is tri-stated, the I2C bus
will float. This makes the I2C bus and its associated
downstream devices inaccessible.
- Hardware fix: Populate resistors R189 and R190 for I2C1
and resistors R228 and R229 for I2C3.
- Software fix: Remove the tri-state option from the PCA954x
driver(PCA954x always on enable status, specify a
channel zero in dts to fix the errata E-00013).

Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Biwen Li <biwen.li@nxp.com>
---
Change in v6:
- adjust log

Change in v5:
- add extra precaution for pca954x_init

Change in v4:
- rename function
pca954x_calculate_chan -> pca954x_regval

Change in v3:
- update subject and description
- add a helper function pca954x_calculate_chan()

Change in v2:
- update subject and description
- add property idle-state

drivers/i2c/muxes/i2c-mux-pca954x.c | 69 +++++++++++++++++++----------
1 file changed, 46 insertions(+), 23 deletions(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index cd8753b29a63..6577ec873f59 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -87,7 +87,7 @@ struct pca954x {

u8 last_chan; /* last register value */
/* MUX_IDLE_AS_IS, MUX_IDLE_DISCONNECT or >= 0 for channel */
- s8 idle_state;
+ s32 idle_state;

struct i2c_client *client;

@@ -237,20 +237,23 @@ static int pca954x_reg_write(struct i2c_adapter *adap,
I2C_SMBUS_BYTE, &dummy);
}

+static u8 pca954x_regval(struct pca954x *data, u8 chan)
+{
+ /* We make switches look like muxes, not sure how to be smarter. */
+ if (data->chip->muxtype == pca954x_ismux)
+ return chan | data->chip->enable;
+ else
+ return 1 << chan;
+}
+
static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
{
struct pca954x *data = i2c_mux_priv(muxc);
struct i2c_client *client = data->client;
- const struct chip_desc *chip = data->chip;
u8 regval;
int ret = 0;

- /* we make switches look like muxes, not sure how to be smarter */
- if (chip->muxtype == pca954x_ismux)
- regval = chan | chip->enable;
- else
- regval = 1 << chan;
-
+ regval = pca954x_regval(data, chan);
/* Only select the channel if its different from the last channel */
if (data->last_chan != regval) {
ret = pca954x_reg_write(muxc->parent, client, regval);
@@ -264,7 +267,7 @@ 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;
+ s32 idle_state;

idle_state = READ_ONCE(data->idle_state);
if (idle_state >= 0)
@@ -410,6 +413,22 @@ static void pca954x_cleanup(struct i2c_mux_core *muxc)
i2c_mux_del_adapters(muxc);
}

+static int pca954x_init(struct i2c_client *client, struct pca954x *data)
+{
+ int ret;
+ if (data->idle_state >= 0) {
+ data->last_chan = pca954x_regval(data, data->idle_state);
+ } else {
+ /* Disconnect multiplexer */
+ data->last_chan = 0;
+ }
+ ret = i2c_smbus_write_byte(client, data->last_chan);
+ if (ret < 0)
+ data->last_chan = 0;
+
+ return ret;
+}
+
/*
* I2C init/probing/exit functions
*/
@@ -419,7 +438,6 @@ static int pca954x_probe(struct i2c_client *client,
struct i2c_adapter *adap = client->adapter;
struct device *dev = &client->dev;
struct device_node *np = dev->of_node;
- bool idle_disconnect_dt;
struct gpio_desc *gpio;
struct i2c_mux_core *muxc;
struct pca954x *data;
@@ -470,23 +488,24 @@ static int pca954x_probe(struct i2c_client *client,
}
}

- /* Write the mux register at addr to verify
+ data->idle_state = MUX_IDLE_AS_IS;
+ if (of_property_read_u32(np, "idle-state", &data->idle_state)) {
+ if (np && of_property_read_bool(np, "i2c-mux-idle-disconnect"))
+ data->idle_state = MUX_IDLE_DISCONNECT;
+ }
+
+ /*
+ * Write the mux register at addr to verify
* that the mux is in fact present. This also
- * initializes the mux to disconnected state.
+ * initializes the mux to a channel
+ * or disconnected state.
*/
- if (i2c_smbus_write_byte(client, 0) < 0) {
+ ret = pca954x_init(client, data);
+ if (ret < 0) {
dev_warn(dev, "probe failed\n");
return -ENODEV;
}

- 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)
goto fail_cleanup;
@@ -538,9 +557,13 @@ static int pca954x_resume(struct device *dev)
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 ret;

- data->last_chan = 0;
- return i2c_smbus_write_byte(client, 0);
+ ret = pca954x_init(client, data);
+ if (ret < 0)
+ dev_err(&client->dev, "failed to verify the mux, the mux maybe not present in fact\n");
+
+ return ret;
}
#endif

--
2.17.1