Re: [PATCH] of: i2c: Add DT bindings for idle states to PCA954x mux driver

[Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>]

Hi Alexander,

Thank you for the patch.

On Monday 15 December 2014 02:25:18 Alexander Sverdlin 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 ?

> Signed-off-by: Alexander Sverdlin <alexander.sverdlin-OYasijW0DpE@public.gmane.org>
> ---
>  .../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 ?

>  #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.

> +		/* 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

-- 
Regards,

Laurent Pinchart