Re: [PATCH v2] i2c: Add support for NXP PCA984x family.

Peter Rosin
2017-12-11T14:59:25Z

On 2017-12-11 15:27, Adrian Fiergolski wrote:
> This patch exetends the current i2c-mux-pca954x driver and adds suuport for
> a newer PCA984x family of the I2C switches and multiplexers from NXP.
> In probe function, the patch supports device ID function, introduced in the
> new family, and checks it against configuration provided by the
> devicetree. Moreover, it also performs software reset which is now
> available for the new devices.
> The reset of the code remains common with the legacy PCA954x devices.
>
> Signed-off-by: Adrian Fiergolski <adrian.fiergolski@cern.ch>
> ---

Somewhere below this triple-dash and before the start of the diff is a good
place to keep a list of changes for the patch.

> .../devicetree/bindings/i2c/i2c-mux-pca954x.txt | 5 +-
> drivers/i2c/muxes/Kconfig | 2 +-
> drivers/i2c/muxes/i2c-mux-pca954x.c | 164 ++++++++++++++++++++-
> 3 files changed, 161 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt
> index aa097045a10e..b428bc0d81b1 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt
> @@ -1,10 +1,13 @@
> * NXP PCA954x I2C bus switch
>
> +The driver supports NXP PCA954x and PCA984x I2C mux/switch devices.
> +
> Required Properties:
>
> - compatible: Must contain one of the following.
> "nxp,pca9540", "nxp,pca9542", "nxp,pca9543", "nxp,pca9544",
> - "nxp,pca9545", "nxp,pca9546", "nxp,pca9547", "nxp,pca9548"
> + "nxp,pca9545", "nxp,pca9546", "nxp,pca9547", "nxp,pca9548",
> + "nxp,pca9846", "nxp,pca9847", "nxp,pca9848", "nxp,pca9849"
>
> - reg: The I2C address of the device.
>
> diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
> index 0f5c8fc36625..5da2e04585a9 100644
> --- a/drivers/i2c/muxes/Kconfig
> +++ b/drivers/i2c/muxes/Kconfig
> @@ -68,7 +68,7 @@ config I2C_MUX_PCA954x
> depends on GPIOLIB || COMPILE_TEST
> help
> If you say yes here you get support for the Philips PCA954x
> - I2C mux/switch devices.
> + and PCA984x I2C mux/switch devices.
>
> This driver can also be built as a module. If so, the module
> will be called i2c-mux-pca954x.
> diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
> index 2ca068d8b92d..88de57ae5b7a 100644
> --- a/drivers/i2c/muxes/i2c-mux-pca954x.c
> +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
> @@ -1,14 +1,16 @@
> /*
> * I2C multiplexer
> *
> + * Copyright (c) 2017 Adrian Fiergolski <Adrian.Fiergolski@cern.ch>
> * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
> * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
> *
> - * This module supports the PCA954x series of I2C multiplexer/switch chips
> - * made by Philips Semiconductors.
> + * This module supports the PCA954x and PCA954x series of I2C multiplexer/switch
> + * chips made by Philips Semiconductors.
> * This includes the:
> * PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
> * and PCA9548.
> + * PCA9846, PCA9847, PCA9848 and PCA9849

This could be formatted in a nicer way.

> *
> * These chips are all controlled via the I2C bus itself, and all have a
> * single 8-bit register. The upstream "parent" bus fans out to two,
> @@ -54,6 +56,12 @@
>
> #define PCA954X_IRQ_OFFSET 4
>
> +//PCA984x family I2C other addresses
> +#define GENERAL_CALL 0x00
> +#define SOFTWARE_RESET 0x06
> +#define DEVICE_ID_ADDRESS 0x7C
> +#define NXP_ID 0x00
> +
> enum pca_type {
> pca_9540,
> pca_9542,
> @@ -63,6 +71,11 @@ enum pca_type {
> pca_9546,
> pca_9547,
> pca_9548,
> + pca_9846,
> + pca_9847,
> + pca_9848,
> + pca_9849,
> +

Drop this empty line.

> };
>
> struct chip_desc {
> @@ -73,6 +86,7 @@ struct chip_desc {
> pca954x_ismux = 0,
> pca954x_isswi
> } muxtype;
> + u16 deviceID; //used by PCA984x family only

Except it isn't used at all. Maybe just drop it?

> };
>
> struct pca954x {
> @@ -89,6 +103,7 @@ struct pca954x {
>
> /* Provide specs for the PCA954x types we know about */
> static const struct chip_desc chips[] = {
> + //954x family

This line adds nothing of interest.

> [pca_9540] = {
> .nchans = 2,
> .enable = 0x4,
> @@ -129,9 +144,36 @@ static const struct chip_desc chips[] = {
> .nchans = 8,
> .muxtype = pca954x_isswi,
> },
> +
> + //984x family

Drop the empty line here as well as below between the other chip_descs.
Also drop the family comment, I don't feel it adds anything relevant.

> + [pca_9846] = {
> + .nchans = 4,
> + .muxtype = pca954x_isswi,
> + .deviceID = 0x10B,
> + },
> +
> + [pca_9847] = {
> + .nchans = 8,
> + .muxtype = pca954x_ismux,
> + .deviceID = 0x108,
> + },
> +
> + [pca_9848] = {
> + .nchans = 8,
> + .muxtype = pca954x_isswi,
> + .deviceID = 0x10A,
> + },
> +
> + [pca_9849] = {
> + .nchans = 4,
> + .muxtype = pca954x_ismux,
> + .deviceID = 0x109,
> + },
> +
> };
>
> static const struct i2c_device_id pca954x_id[] = {
> + //954x family

Drop this.

> { "pca9540", pca_9540 },
> { "pca9542", pca_9542 },
> { "pca9543", pca_9543 },
> @@ -140,12 +182,20 @@ static const struct i2c_device_id pca954x_id[] = {
> { "pca9546", pca_9546 },
> { "pca9547", pca_9547 },
> { "pca9548", pca_9548 },
> +
> + //984x family

Drop the empty line and the comment.

> + { "pca9846", pca_9846 },
> + { "pca9847", pca_9847 },
> + { "pca9848", pca_9848 },
> + { "pca9849", pca_9849 },
> +

Drop the empty line.

> { }
> };
> MODULE_DEVICE_TABLE(i2c, pca954x_id);
>
> #ifdef CONFIG_OF
> static const struct of_device_id pca954x_of_match[] = {
> + //954x family

Dito.

> { .compatible = "nxp,pca9540", .data = &chips[pca_9540] },
> { .compatible = "nxp,pca9542", .data = &chips[pca_9542] },
> { .compatible = "nxp,pca9543", .data = &chips[pca_9543] },
> @@ -154,6 +204,14 @@ static const struct of_device_id pca954x_of_match[] = {
> { .compatible = "nxp,pca9546", .data = &chips[pca_9546] },
> { .compatible = "nxp,pca9547", .data = &chips[pca_9547] },
> { .compatible = "nxp,pca9548", .data = &chips[pca_9548] },
> +
> +
> + //984x family

Dito.

> + { .compatible = "nxp,pca9846", .data = &chips[pca_9846] },
> + { .compatible = "nxp,pca9847", .data = &chips[pca_9847] },
> + { .compatible = "nxp,pca9848", .data = &chips[pca_9848] },
> + { .compatible = "nxp,pca9849", .data = &chips[pca_9849] },
> +

Dito.

> {}
> };
> MODULE_DEVICE_TABLE(of, pca954x_of_match);
> @@ -304,6 +362,78 @@ static void pca954x_cleanup(struct i2c_mux_core *muxc)
> i2c_mux_del_adapters(muxc);
> }
>
> +/*
> + * Part of probe function specific for pca954x family
> + */
> +inline int _pca954x_probe(struct i2c_client *client,
> + const struct i2c_device_id *id){

The brace should be on a line by itself. No need to manually
say inline, any decent compiler will inline whatever is
appropriate, just use static instead. And lose the leading
underscore.

> +
> + /* 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)
> + return -ENODEV;
> +
> + return 0;
> +}
> +
> +/*
> + * Part of probe function specific for pca984x family
> + */
> +inline int _pca984x_probe(struct i2c_client *client,
> + const struct i2c_device_id *id){

Dito.

> +
> + struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
> + union i2c_smbus_data device_id_raw;
> + u16 manufacturer_id; //12 bits
> +
> + if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
> + dev_warn(&client->dev, "PCA9846 family: I2c adapter doesn't support I2C_FUNC_SMBUS_WRITE_BYTE_DATA");
> + return -ENODEV;
> + }
> +
> + if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
> + dev_warn(&client->dev, "PCA9846 family: I2c adapter doesn't support I2C_FUNC_SMBUS_READ_I2C_BLOCK");
> + return -ENODEV;
> + }
> +
> + /*
> + * Software reset
> + */

This could be a single line comment.

> + if (i2c_smbus_xfer(client->adapter, GENERAL_CALL, client->flags,
> + I2C_SMBUS_WRITE, SOFTWARE_RESET, I2C_SMBUS_BYTE, NULL) < 0) {
> + dev_warn(&client->dev, "PCA9846 family: Sofrware reset failed\n");
> + return -ENODEV;
> + }

This is extremely invasive, and not appropriate for this driver. Do you
need it? Why?

> +
> + /*
> + * Get device ID
> + */

This could be a single line comment.

> + device_id_raw.block[0] = 3; //read 3 bytes
> + if (i2c_smbus_xfer(client->adapter, DEVICE_ID_ADDRESS, client->flags,
> + I2C_SMBUS_READ, client->addr << 1,
> + I2C_SMBUS_I2C_BLOCK_DATA, &device_id_raw)) {
> + dev_warn(&client->dev, "PCA9846 family: Get device ID failed\n");
> + return -ENODEV;
> + }
> +
> + //Device ID contains only 3 bytes

I don't much care for // comments, and the missing space after them is especially
disturbing.

> + if (device_id_raw.block[0] != 3) {
> + dev_warn(&client->dev, "PCA9846 family: Get device ID failed\n");
> + return -ENODEV;
> + }
> +
> + //Check manufacturer ID (12 bits)
> + manufacturer_id = ((u16) device_id_raw.block[1] << 4) | (device_id_raw.block[2] >> 4);

This is just broken, and works by chance only because NXP_ID happens to be
zero.

I get the feeling that you don't need to go digging up the manufacturer. That
way you could avoid the split of the probe for the two families. So, what do
you gain by verifying the manufacturer?

> + if (manufacturer_id != NXP_ID) {
> + dev_warn(&client->dev, "PCA9846 family: Manufacturer ID does not match NXP\n");
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> /*
> * I2C init/probing/exit functions
> */
> @@ -339,11 +469,29 @@ static int pca954x_probe(struct i2c_client *client,
> if (IS_ERR(gpio))
> return PTR_ERR(gpio);
>
> - /* 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) {
> + switch (id->driver_data) {
> + case pca_9540:
> + case pca_9542:
> + case pca_9543:
> + case pca_9544:
> + case pca_9545:
> + case pca_9546:
> + case pca_9547:
> + case pca_9548:
> + ret = _pca954x_probe(client, id);
> + break;
> + case pca_9846:
> + case pca_9847:
> + case pca_9848:
> + case pca_9849:
> + ret = _pca984x_probe(client, id);
> + break;
> + default: //unknown device
> + ret = -ENODEV;
> + break;
> + }
> +
> + if (ret < 0) {
> dev_warn(&client->dev, "probe failed\n");
> return -ENODEV;
> }
> @@ -443,6 +591,6 @@ static struct i2c_driver pca954x_driver = {
>
> module_i2c_driver(pca954x_driver);
>
> -MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
> +MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>, Adrian Fiergolski <Adrian.Fiergolski@cern.ch>");
> MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
> MODULE_LICENSE("GPL v2");
>