linux-kernel - Re: [PATCH 2/2] i2c: mux: pca954x: replace property i2c-mux-idle-disconnect

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Date:   Mon, 14 Oct 2019 16:03:08 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Biwen Li <biwen.li@....com>,
        "leoyang.li@....com" <leoyang.li@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/2] i2c: mux: pca954x: replace property
 i2c-mux-idle-disconnect

On 2019-10-14 13:25, Biwen Li wrote:
> This replaces property i2c-mux-idle-disconnect with idle-state
> 
> Signed-off-by: Biwen Li <biwen.li@....com>
> ---
>  drivers/i2c/muxes/i2c-mux-pca954x.c | 44 ++++++++++++++++++++---------
>  1 file changed, 31 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
> index 923aa3a5a3dc..a330929c4d67 100644
> --- a/drivers/i2c/muxes/i2c-mux-pca954x.c
> +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
> @@ -86,7 +86,7 @@ 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;
>  
> @@ -256,7 +256,7 @@ 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)
> @@ -411,7 +411,6 @@ 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;
> @@ -462,22 +461,31 @@ static int pca954x_probe(struct i2c_client *client,
>  		}
>  	}
>  
> +	if (of_property_read_u32(np, "idle-state", &data->idle_state))
> +		data->idle_state = MUX_IDLE_AS_IS;
> +
>  	/* Write the mux register at addr to verify
>  	 * that the mux is in fact present. This also
>  	 * initializes the mux to disconnected state.
>  	 */
> -	if (i2c_smbus_write_byte(client, 0) < 0) {
> +	if (data->idle_state >= 0){

Space before {

> +		data->last_chan = data->idle_state;

data->last_chan should have the actual register value, i.e. (untested)

		if (data->chip->muxtype == pca954x_ismux)
			data->last_chan = data->idle_state | data->chip->enable;
		else
			data->last_chan = 1 << data->idle_state;

		ret = i2c_smbus_write_byte(client, data->last_chan);

But since this regval calculation is now needed in three places, it should
be moved to a helper function.

> +		/* Always enable multiplexer */
> +		ret = i2c_smbus_write_byte(client, data->last_chan |
> +				(data->chip->muxtype == pca954x_ismux ?
> +				 data->chip->enable : 0));
> +	}
> +	else{

Space before {

Naturally, you have the exact same issues in the pca954x_resume hunk, below.

> +		data->last_chan = 0;		   /* force the first selection */
> +		/* Disconnect multiplexer */
> +		ret = i2c_smbus_write_byte(client, data->last_chan);
> +	}
> +
> +	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;

In case the idle-state property is missing, you need to fall back to the
old behavior and handle i2c-mux-idle-disconnect as before.

Cheers,
Peter

>  
>  	ret = pca954x_irq_setup(muxc);
>  	if (ret)
> @@ -531,8 +539,18 @@ static int pca954x_resume(struct device *dev)
>  	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
>  	struct pca954x *data = i2c_mux_priv(muxc);
>  
> -	data->last_chan = 0;
> -	return i2c_smbus_write_byte(client, 0);
> +	if (data->idle_state >= 0){
> +		data->last_chan = data->idle_state;
> +		/* Always enable multiplexer */
> +		return i2c_smbus_write_byte(client, data->last_chan |
> +				(data->chip->muxtype == pca954x_ismux ?
> +				 data->chip->enable : 0));
> +	}
> +	else{
> +		data->last_chan = 0;
> +		/* Disconnect multiplexer */
> +		return i2c_smbus_write_byte(client, data->last_chan);
> +	}
>  }
>  #endif
>  
>