Hello Laurent,
On 15/12/14 09:40, ext Laurent Pinchart wrote:
>> of: i2c: Add DT bindings for idle states to PCA954x mux driver
>>
>> Introduce two new device tree bindings to specify idle state of PCA954x
>> family of I2C multiplexors:
>> - idle-state: specifies particular child bus to be selected in idle;
>> - idle-disconnect: signals that mux should disconnect all child buses in
>> idle;
>
> Could you please briefly explain your use case(s) for those two properties ?
idle-state specifies which bus will be connected when there is no data transfer.
i2c-mux-gpio also has "idle-state" (though, it can replace both connect and
disconnect cases in my patch). i2c-mux-pinctrl has special "idle" convention,
specifying idle state as last in the list of states. Again, it can serve for
both my properties.
idle-disconnect is what we actually use for some security reasons (so that
I2C bus of the external SFP cage is not connected to the rest of I2C bus
in idle).
>> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxx>
>> ---
>> .../devicetree/bindings/i2c/i2c-mux-pca954x.txt | 3 +
>> drivers/i2c/muxes/i2c-mux-pca954x.c | 51 +++++++++++++++--
>> 2 files changed, 48 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt
>> b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt index
>> 34a3fb6..1fbe287 100644
>> --- a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt
>> +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt
>> @@ -16,6 +16,9 @@ Required Properties:
>> Optional Properties:
>>
>> - reset-gpios: Reference to the GPIO connected to the reset input.
>> + - idle-state: Child bus connected in idle state (specified by its "reg"
>> value) + - idle-disconnect: Boolean; if defined, forces mux to disconnect
>> all children + in idle state
>>
>>
>> Example:
>> diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c
>> b/drivers/i2c/muxes/i2c-mux-pca954x.c index ec11b40..69cf603 100644
>> --- a/drivers/i2c/muxes/i2c-mux-pca954x.c
>> +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
>> @@ -43,6 +43,7 @@
>> #include <linux/module.h>
>> #include <linux/pm.h>
>> #include <linux/slab.h>
>> +#include <linux/of.h>
>
> Could you please keep headers sorted alphabetically ?
Yes...
>> #define PCA954X_MAX_NCHANS 8
>>
>> @@ -62,6 +63,8 @@ struct pca954x {
>> struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
>>
>> u8 last_chan; /* last register value */
>> + bool idle_disconnect;
>> + s8 idle_chan; /* valid if not negative */
>> };
>>
>> struct chip_desc {
>> @@ -172,10 +175,20 @@ static int pca954x_deselect_mux(struct i2c_adapter
>> *adap, void *client, u32 chan)
>> {
>> struct pca954x *data = i2c_get_clientdata(client);
>> + struct pca954x_platform_data *pdata =
>> + dev_get_platdata(&((struct i2c_client *)client)->dev);
>> +
>> + if ((pdata && pdata->modes[chan].deselect_on_exit) ||
>> + data->idle_disconnect) {
>
> I would copy pdata->modes[chan].deselect_on_exit to data->idle_disconnect in
> the probe function, so you could avoiding accessing pdata here.
Unfortunately, this pdata has different (per-channel) semantics. I cannot really
understand, why it was done this way, but anyway it's not possible to use one global
bit to represent per-channel bits without changing the behavior.
I'm not keen to brake out-of-tree code (if any), but may be it will be decided to
drop this per-channel deselect_on_exit, because it's not used at least in the
kernel tree...
>> + /* Deselect active channel */
>> + data->last_chan = 0;
>> + return pca954x_reg_write(adap, client, data->last_chan);
>> + }
>>
>> - /* Deselect active channel */
>> - data->last_chan = 0;
>> - return pca954x_reg_write(adap, client, data->last_chan);
>> + if (data->idle_chan >= 0)
>> + return pca954x_select_chan(adap, client, data->idle_chan);
>> +
>> + return 0;
>> }
>>
>> /*
>> @@ -186,6 +199,7 @@ static int pca954x_probe(struct i2c_client *client,
>> {
>> struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
>> struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev);
>> + struct device_node *of_node = client->dev.of_node;
>> struct gpio_desc *gpio;
>> int num, force, class;
>> struct pca954x *data;
>> @@ -216,6 +230,27 @@ static int pca954x_probe(struct i2c_client *client,
>>
>> data->type = id->driver_data;
>> data->last_chan = 0; /* force the first selection */
>> + data->idle_chan = -1; /* no forced idle state */
>> +
>> + if (of_node) {
>> + u32 ch;
>> +
>> + if (of_property_read_bool(of_node, "idle-disconnect"))
>> + data->idle_disconnect = true;
>> +
>> + if (!of_property_read_u32_index(of_node, "idle-state", 0, &ch)) {
>> + if (ch < PCA954X_MAX_NCHANS) {
>> + data->idle_chan = ch;
>> + /* Force idle state from the beginning */
>> + ret = pca954x_select_chan(adap, client, ch);
>> + if (ret)
>> + return ret;
>> + } else {
>> + dev_warn(&client->dev,
>> + "Invalid idle-state property\n");
>> + }
>> + }
>> + }
>>
>> /* Now create an adapter for each channel */
>> for (num = 0; num < chips[data->type].nchans; num++) {
>> @@ -234,8 +269,7 @@ static int pca954x_probe(struct i2c_client *client,
>> data->virt_adaps[num] =
>> 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);
>>
>> if (data->virt_adaps[num] == NULL) {
>> ret = -ENODEV;
>> @@ -281,7 +315,12 @@ static int pca954x_resume(struct device *dev)
>> struct pca954x *data = i2c_get_clientdata(client);
>>
>> data->last_chan = 0;
>> - return i2c_smbus_write_byte(client, 0);
>> + /* Restore idle state on resume */
>> + if (data->idle_chan >= 0)
>> + return pca954x_select_chan(to_i2c_adapter(client->dev.parent),
>> + client, data->idle_chan);
>> + else
>> + return i2c_smbus_write_byte(client, 0);
>> }
>> #endif
>
--
Best regards,
Alexander Sverdlin.
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