Date:   Wed, 16 Oct 2019 03:24:26 +0000
From:   Biwen Li <biwen.li@....com>
To:     Peter Rosin <peda@...ntia.se>, Leo Li <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: [EXT] Re: [v2,2/2] i2c: mux: pca954x: add property idle-state

> 
> On 2019-10-15 06:48, Biwen Li wrote:
> > This adds property idle-state
> >
> > Signed-off-by: Biwen Li <biwen.li@....com>
> > ---
> > Change in v2:
> >       - update subject and description
> >       - add property idle-state
> >
> >  drivers/i2c/muxes/i2c-mux-pca954x.c | 47
> > ++++++++++++++++++-----------
> >  1 file changed, 30 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c
> > b/drivers/i2c/muxes/i2c-mux-pca954x.c
> > index 923aa3a5a3dc..8ec586342b92 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)
> > @@ -402,6 +402,25 @@ 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) {
> > +     /*
> > +      * Write the mux register at addr to verify
> > +      * that the mux is in fact present. This also
> > +      * initializes the mux to disconnected state.
> > +      */
> 
> This comment belongs in pca954x_probe, before the call to this function.
> However, the comment may now be be wrong since the mux is not always
> initialized to the disconnected state.
Got it, I will update it in v3.
> 
> > +     if (data->idle_state >= 0) {
> > +             /* Always enable multiplexer */
> 
> While I understand that it is important for your case that the mux is always
> enabled, this is just a side effect of having a specific idle-state. I suggest that
> you remove this comment.
Got it, I will remove it in v3.
> 
> > +             if (data->chip->muxtype == pca954x_ismux)
> > +                     data->last_chan = data->idle_state |
> data->chip->enable;
> > +             else
> > +                     data->last_chan = 1 << data->idle_state;
> 
> The meat of this "if" is still duplicated, I was suggesting a helper that only did
> the regval calculation so that the new helper could also be used from
> pca954x_select_chan.o
> 
> > +     } else {
> > +             /* Disconnect multiplexer */
> > +             data->last_chan = 0; /* force the first selection */
> 
> These two comments should be combined.
Got it.
> 
> > +     }
> > +     return i2c_smbus_write_byte(client, data->last_chan); }
> >  /*
> >   * I2C init/probing/exit functions
> >   */
> > @@ -411,7 +430,6 @@ 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 +480,18 @@ static int pca954x_probe(struct i2c_client
> *client,
> >               }
> >       }
> >
> > -     /* 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 (of_property_read_u32(np, "idle-state", &data->idle_state))
> > +             data->idle_state = MUX_IDLE_AS_IS;
> > +
> > +     if (of_property_read_bool(np, "i2c-mux-idle-disconnect"))
> > +             data->idle_state = MUX_IDLE_DISCONNECT;
> 
> I think you should ignore i2c-mux-idle-disconnect if idle-state is present.
> I.e. move this "if" statement into the body of the former "if". Also, you have
> broken things if np is NULL.
Got it, I will modify it in v3.
> 
> Cheers,
> Peter
> 
> > +
> > +     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)
> > @@ -531,8 +545,7 @@ 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);
> > +     return pca954x_init(client, data);
> >  }
> >  #endif
> >
> >

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