linux-kernel - Re: [PATCH v2 2/3] hwmon (xdpe12284): Add support for xdpe11280

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Date:   Thu, 17 Feb 2022 07:20:47 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marcello Sylvester Bauer <sylv@...v.io>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 2/3] hwmon (xdpe12284): Add support for xdpe11280

On 2/17/22 06:41, Marcello Sylvester Bauer wrote:
> Add support for another family of Infineon Multi-phase controllers.
> The xdpe11280 uses linear instead of vid data format for VOUT.
> Add the required logic to detect VOUT_MODE during identification,
> and set the format accordingly.
> 
This talks about the chip, but ...

> Signed-off-by: Marcello Sylvester Bauer <sylv@...v.io>
> ---
>   Documentation/hwmon/xdpe12284.rst | 10 +++++++---
>   drivers/hwmon/pmbus/xdpe12284.c   | 17 ++++++++++++++++-
>   2 files changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/hwmon/xdpe12284.rst b/Documentation/hwmon/xdpe12284.rst
> index 67d1f87808e5..e9a5a19b0c3d 100644
> --- a/Documentation/hwmon/xdpe12284.rst
> +++ b/Documentation/hwmon/xdpe12284.rst
> @@ -5,6 +5,10 @@ Kernel driver xdpe122
>   
>   Supported chips:
>   
> +  * Infineon XDPE11280
> +
> +    Prefix: 'xdpe11280'
> +
>     * Infineon XDPE12254
>   
>       Prefix: 'xdpe12254'
> @@ -20,9 +24,9 @@ Authors:
>   Description
>   -----------
>   
> -This driver implements support for Infineon Multi-phase XDPE122 family
> -dual loop voltage regulators.
> -The family includes XDPE12284 and XDPE12254 devices.
> +This driver implements support for Infineon Multi-phase XDPE112 and XDPE122
> +family dual loop voltage regulators.
> +These families include XDPE11280, XDPE12284 and XDPE12254 devices.
>   The devices from this family complaint with:

Hmm, s/complaint/compliant/.

Anyway, is it still correct that the XDPE11280 is compliant with the
Intel specifications ? The datasheet isn't public, so I can not check myself
what the chip actually supports.

>   
>   - Intel VR13 and VR13HC rev 1.3, IMVP8 rev 1.2 and IMPVP9 rev 1.3 DC-DC
> diff --git a/drivers/hwmon/pmbus/xdpe12284.c b/drivers/hwmon/pmbus/xdpe12284.c
> index b07da06a40c9..ec947c697670 100644
> --- a/drivers/hwmon/pmbus/xdpe12284.c
> +++ b/drivers/hwmon/pmbus/xdpe12284.c
> @@ -27,6 +27,9 @@ static int xdpe122_read_word_data(struct i2c_client *client, int page,
>   	s32 mantissa;
>   	int ret;
>   
> +	if (info->format[PSC_VOLTAGE_OUT] == linear)
> +		return -ENODATA;
> +
>   	switch (reg) {
>   	case PMBUS_VOUT_OV_FAULT_LIMIT:
>   	case PMBUS_VOUT_UV_FAULT_LIMIT:
> @@ -75,9 +78,19 @@ static int xdpe122_read_word_data(struct i2c_client *client, int page,
>   static int xdpe122_identify(struct i2c_client *client,
>   			    struct pmbus_driver_info *info)
>   {
> -	u8 vout_params;
> +	u8 vout_mode, vout_params;
>   	int i, ret;
>   
> +	ret = pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE);
> +	if (ret < 0)
> +		return ret;
> +
> +	vout_mode = ret >> 5;
> +	if (vout_mode == 0) {
> +		info->format[PSC_VOLTAGE_OUT] = linear;
> +		return 0;
> +	}

.... the code above is not chip dependent but this code checks the
mode register on page 0. At the very least this is confusing.

What the driver should do instead is to check the chip type during
probe and make the necessary changes there, ie set the output format
for xdpe11280 to linear and drop the pointers to the .identify
and .read_word_data.

Guenter

> +
>   	for (i = 0; i < XDPE122_PAGE_NUM; i++) {
>   		/* Read the register with VOUT scaling value.*/
>   		ret = pmbus_read_byte_data(client, i, PMBUS_VOUT_MODE);
> @@ -140,6 +153,7 @@ static int xdpe122_probe(struct i2c_client *client)
>   }
>   
>   static const struct i2c_device_id xdpe122_id[] = {
> +	{"xdpe11280", 0},
>   	{"xdpe12254", 0},
>   	{"xdpe12284", 0},
>   	{}
> @@ -148,6 +162,7 @@ static const struct i2c_device_id xdpe122_id[] = {
>   MODULE_DEVICE_TABLE(i2c, xdpe122_id);
>   
>   static const struct of_device_id __maybe_unused xdpe122_of_match[] = {
> +	{.compatible = "infineon,xdpe11280"},
>   	{.compatible = "infineon,xdpe12254"},
>   	{.compatible = "infineon,xdpe12284"},
>   	{}