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Date: Fri, 15 Nov 2019 10:21:22 +0000
From: Biwen Li <biwen.li@....com>
To: Biwen Li <biwen.li@....com>, "peda@...ntia.se" <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: [v5,2/3] i2c: mux: pca954x: support property idle-state
Hi Peter,
Any comments?
If no comments, could you give me a reviewed-by?
Best Regards,
Biwen Li
> This supports property idle-state,if present, overrides i2c-mux-idle-disconnect.
>
> My use cases:
> - Use the property idle-state to fix
> an errata on LS2085ARDB and LS2088ARDB.
> - Errata id: E-00013(board LS2085ARDB and
> LS2088ARDB revision on Rev.B, Rev.C and Rev.D).
> - About E-00013:
> - Description: I2C1 and I2C3 buses
> are missing pull-up.
> - Impact: When the PCA954x device is tri-stated, the I2C bus
> will float. This makes the I2C bus and its associated
> downstream devices inaccessible.
> - Hardware fix: Populate resistors R189 and R190 for I2C1
> and resistors R228 and R229 for I2C3.
> - Software fix: Remove the tri-state option from the PCA954x
> driver(PCA954x always on enable status, specify a
> channel zero in dts to fix the errata E-00013).
>
> Signed-off-by: Biwen Li <biwen.li@....com>
> ---
> Change in v5:
> - add extra precaution for pca954x_init
>
> 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 | 67 +++++++++++++++++++----------
> 1 file changed, 44 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c
> b/drivers/i2c/muxes/i2c-mux-pca954x.c
> index 923aa3a5a3dc..218ba1a5ed7e 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. */
> + 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, 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 +405,25 @@ 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) {
> + int ret;
> + if (data->idle_state >= 0) {
> + data->last_chan = pca954x_regval(data, data->idle_state);
> + } else {
> + /* Disconnect multiplexer */
> + data->last_chan = 0;
> + }
> + ret = i2c_smbus_write_byte(client, data->last_chan);
> + if (ret < 0) {
> + data->last_chan = 0;
> + dev_err(&client->dev, "failed to verify the mux, \
> + the mux maybe not present in fact\n");
> + }
> +
> + return ret;
> +}
> +
> /*
> * I2C init/probing/exit functions
> */
> @@ -411,7 +433,6 @@ 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 +483,24 @@ 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 +553,7 @@ 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
>
> --
> 2.17.1
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