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Message-ID: <07b1e1d8-4112-d9b1-2a05-21da09fa020c@axentia.se>
Date: Mon, 21 Oct 2019 13:20:58 +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: [v4,2/2] i2c: mux: pca954x: support property idle-state
On 2019-10-21 10:00, Biwen Li wrote:
> This supports property idle-state
>
You should expand this a little bit to explain that idle-state, if present,
overrides i2c-mux-idle-disconnect. You could also mention your use case
where you need to avoid disconnects on probe/resume.
> Signed-off-by: Biwen Li <biwen.li@....com>
> ---
> 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 | 59 ++++++++++++++++++-----------
> 1 file changed, 36 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
> index 923aa3a5a3dc..e566c4cd8ba5 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;
>
> @@ -229,20 +229,23 @@ 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 */
I know you are just moving the comment around, but please fix the sentence
to start with a capital letter and end with a period. Sorry I didn't
catch this in v3.
> + 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, (u8)(chan & 0xff));
Both a mask and a cast to do what the compiler should be doing all by itself?
If you need to kill a warning, or something, please do just one or them. But
personally I prefer the short, sweet and uncluttered:
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);
> @@ -256,7 +259,7 @@ 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 +405,17 @@ 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)
> +{
> + if (data->idle_state >= 0) {
> + data->last_chan = pca954x_regval(data, (u8)(data->idle_state & 0xff));
Dito.
> + } else {
> + /* Disconnect multiplexer */
> + data->last_chan = 0;
> + }
> + return i2c_smbus_write_byte(client, data->last_chan);
Here's another thing I missed in the earlier iterations. If i2c_smbus_write_byte
fails here, I think you should set data->last_chan to zero. For the call from
probe it obviously doesn't matter much, but I think the call during resume is
better off with such extra precaution in place.
Cheers,
Peter
> +}
> +
> /*
> * I2C init/probing/exit functions
> */
> @@ -411,7 +425,6 @@ 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;
> @@ -462,23 +475,24 @@ 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;
> @@ -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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