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Date:   Thu, 8 Apr 2021 19:08:26 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Václav Kubernát <kubernat@...net.cz>
Cc:     Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
        linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] hwmon: Add driver for fsp-3y PSUs and PDUs

On 4/8/21 6:27 PM, Václav Kubernát wrote:
> This patch adds support for these devices:
> - YH-5151E - the PDU
> - YM-2151E - the PSU
> 
> The device datasheet says that the devices support PMBus 1.2, but in my
> testing, a lot of the commands aren't supported and if they are, they
> sometimes behave strangely or inconsistently. For example, writes to the
> PAGE command requires using PEC, otherwise the write won't work and the
> page won't switch, even though, the standard says that PEC is opiotnal.
> On the other hand, writes the SMBALERT don't require PEC. Because of
> this, the driver is mostly reverse engineered with the help of a tool
> called pmbus_peek written by David Brownell (and later adopted by my
> colleague Jan Kundrát).
> 
> The device also has some sort of a timing issue when switching pages,
> which is explained further in the code.
> 
> Because of this, the driver support is limited. It exposes only the
> values, that have been tested to work correctly.
> 
> Signed-off-by: Václav Kubernát <kubernat@...net.cz>
> ---
>  Documentation/hwmon/fsp-3y.rst |  26 ++++
>  drivers/hwmon/pmbus/Kconfig    |  10 ++
>  drivers/hwmon/pmbus/Makefile   |   1 +
>  drivers/hwmon/pmbus/fsp-3y.c   | 236 +++++++++++++++++++++++++++++++++
>  4 files changed, 273 insertions(+)
>  create mode 100644 Documentation/hwmon/fsp-3y.rst
>  create mode 100644 drivers/hwmon/pmbus/fsp-3y.c
> 
> diff --git a/Documentation/hwmon/fsp-3y.rst b/Documentation/hwmon/fsp-3y.rst
> new file mode 100644
> index 000000000000..68a547021846
> --- /dev/null
> +++ b/Documentation/hwmon/fsp-3y.rst
> @@ -0,0 +1,26 @@
> +Kernel driver fsp3y
> +======================
> +Supported devices:
> +  * 3Y POWER YH-5151E
> +  * 3Y POWER YM-2151E
> +
> +Author: Václav Kubernát <kubernat@...net.cz>
> +
> +Description
> +-----------
> +This driver implements limited support for two 3Y POWER devices.
> +
> +Sysfs entries
> +-------------
> +in1_input            input voltage
> +in2_input            12V output voltage
> +in3_input            5V output voltage
> +curr1_input          input current
> +curr2_input          12V output current
> +curr3_input          5V output current
> +fan1_input           fan rpm
> +temp1_input          temperature 1
> +temp2_input          temperature 2
> +temp3_input          temperature 3
> +power1_input         input power
> +power2_input         output power
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 03606d4298a4..9d12d446396c 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -56,6 +56,16 @@ config SENSORS_BEL_PFE
>  	  This driver can also be built as a module. If so, the module will
>  	  be called bel-pfe.
>  
> +config SENSORS_FSP_3Y
> +	tristate "FSP/3Y-Power power supplies"
> +	help
> +	  If you say yes here you get hardware monitoring support for
> +	  FSP/3Y-Power hot-swap power supplies.
> +	  Supported models: YH-5151E, YM-2151E
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called fsp-3y.
> +
>  config SENSORS_IBM_CFFPS
>  	tristate "IBM Common Form Factor Power Supply"
>  	depends on LEDS_CLASS
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index 6a4ba0fdc1db..bfe218ad898f 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_SENSORS_PMBUS)	+= pmbus.o
>  obj-$(CONFIG_SENSORS_ADM1266)	+= adm1266.o
>  obj-$(CONFIG_SENSORS_ADM1275)	+= adm1275.o
>  obj-$(CONFIG_SENSORS_BEL_PFE)	+= bel-pfe.o
> +obj-$(CONFIG_SENSORS_FSP_3Y)	+= fsp-3y.o
>  obj-$(CONFIG_SENSORS_IBM_CFFPS)	+= ibm-cffps.o
>  obj-$(CONFIG_SENSORS_INSPUR_IPSPS) += inspur-ipsps.o
>  obj-$(CONFIG_SENSORS_IR35221)	+= ir35221.o
> diff --git a/drivers/hwmon/pmbus/fsp-3y.c b/drivers/hwmon/pmbus/fsp-3y.c
> new file mode 100644
> index 000000000000..f03c4e27ec8c
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/fsp-3y.c
> @@ -0,0 +1,236 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Hardware monitoring driver for FSP 3Y-Power PSUs
> + *
> + * Copyright (c) 2021 Václav Kubernát, CESNET
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include "pmbus.h"
> +
> +#define YM2151_PAGE_12V_LOG	0x00
> +#define YM2151_PAGE_12V_REAL	0x00
> +#define YM2151_PAGE_5VSB_LOG	0x01
> +#define YM2151_PAGE_5VSB_REAL	0x20
> +#define YH5151E_PAGE_12V_LOG	0x00
> +#define YH5151E_PAGE_12V_REAL	0x00
> +#define YH5151E_PAGE_5V_LOG	0x01
> +#define YH5151E_PAGE_5V_REAL	0x10
> +#define YH5151E_PAGE_3V3_LOG	0x02
> +#define YH5151E_PAGE_3V3_REAL	0x11
> +
> +enum chips {
> +	ym2151e,
> +	yh5151e
> +};
> +
> +struct fsp3y_data {
> +	struct pmbus_driver_info info;
> +	enum chips chip;
> +	int page;
> +};
> +
> +#define to_fsp3y_data(x) container_of(x, struct fsp3y_data, info)
> +
> +static int page_log_to_page_real(int page_log, enum chips chip)
> +{
> +	switch (chip) {
> +	case ym2151e:
> +		switch (page_log) {
> +		case YM2151_PAGE_12V_LOG:
> +			return YM2151_PAGE_12V_REAL;
> +		case YM2151_PAGE_5VSB_LOG:
> +			return YM2151_PAGE_5VSB_REAL;
> +		}
> +		return -EINVAL;
> +	case yh5151e:
> +		switch (page_log) {
> +		case YH5151E_PAGE_12V_LOG:
> +			return YH5151E_PAGE_12V_REAL;
> +		case YH5151E_PAGE_5V_LOG:
> +			return YH5151E_PAGE_5V_LOG;
> +		case YH5151E_PAGE_3V3_LOG:
> +			return YH5151E_PAGE_3V3_REAL;
> +		}
> +		return -EINVAL;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int set_page(struct i2c_client *client, int page_log)
> +{
> +	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
> +	struct fsp3y_data *data = to_fsp3y_data(info);
> +	int rv;
> +	int page_real;
> +
> +	if (page_log < 0)
> +		return 0;
> +
> +	page_real = page_log_to_page_real(page_log, data->chip);
> +	if (page_real < 0)
> +		return page_real;
> +
> +	if (data->page != page_real) {
> +		rv = pmbus_set_page(client, page_real, 0xff);

Uh, that won't work. pmbus_set_page() indexes its internal data with the
passed page number, or in other words needs to use the logical page number.
You'll have to call i2c_smbus_write_byte_data(client, PMBUS_PAGE, page_real)
directly here.

> +		if (rv < 0)
> +			return rv;
> +
> +		data->page = page_real;
> +
> +		/* Testing showed that the device has a timing issue. After
> +		 * setting a page, it takes a while, before the device actually
> +		 * gives the correct values from the correct page. 20 ms was
> +		 * tested to be enough to not give wrong values (15 ms wasn't
> +		 * enough)
> +		 */
> +		usleep_range(20000, 30000);
> +	}
> +
> +	return 0;
> +}
> +
> +static int fsp3y_read_byte_data(struct i2c_client *client, int page, int reg)
> +{
> +	int rv;
> +
> +	rv = set_page(client, page);
> +	if (rv < 0)
> +		return rv;
> +
> +	return i2c_smbus_read_byte_data(client, reg);
> +}
> +
> +static int fsp3y_read_word_data(struct i2c_client *client, int page, int phase, int reg)
> +{
> +	int rv;
> +
> +	switch (reg) {
> +	case PMBUS_READ_FAN_SPEED_1:
> +	case PMBUS_READ_IIN:
> +	case PMBUS_READ_IOUT:
> +	case PMBUS_READ_PIN:
> +	case PMBUS_READ_POUT:
> +	case PMBUS_READ_TEMPERATURE_1:
> +	case PMBUS_READ_TEMPERATURE_2:
> +	case PMBUS_READ_TEMPERATURE_3:
> +	case PMBUS_READ_VIN:
> +	case PMBUS_READ_VOUT:
> +	case PMBUS_STATUS_WORD:
> +		break;
> +	default:

Add a comment here, explaining why other registers are ignored (because
it is unknown what exactly they report).

> +		return -ENXIO;
> +	}
> +
> +	rv = set_page(client, page);
> +	if (rv < 0)
> +		return rv;
> +
> +	return i2c_smbus_read_word_data(client, reg);
> +}
> +
> +struct pmbus_driver_info fsp3y_info[] = {
> +	[ym2151e] = {
> +		.pages = 2,
> +		.func[YM2151_PAGE_12V_LOG] =
> +			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
> +			PMBUS_HAVE_PIN | PMBUS_HAVE_POUT  |
> +			PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 |
> +			PMBUS_HAVE_VIN | PMBUS_HAVE_IIN |
> +			PMBUS_HAVE_FAN12,
> +		.func[YM2151_PAGE_5VSB_LOG] =
> +			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT,
> +			PMBUS_HAVE_IIN,
> +		.read_word_data = fsp3y_read_word_data,
> +		.read_byte_data = fsp3y_read_byte_data,
> +	},
> +	[yh5151e] = {
> +		.pages = 3,
> +		.func[YH5151E_PAGE_12V_LOG] =
> +			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
> +			PMBUS_HAVE_POUT  |
> +			PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 | PMBUS_HAVE_TEMP3,
> +		.func[YH5151E_PAGE_5V_LOG] =
> +			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
> +			PMBUS_HAVE_POUT,
> +		.func[YH5151E_PAGE_3V3_LOG] =
> +			PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
> +			PMBUS_HAVE_POUT,
> +		.read_word_data = fsp3y_read_word_data,
> +		.read_byte_data = fsp3y_read_byte_data,
> +	}
> +};
> +
> +static int fsp3y_detect(struct i2c_client *client)
> +{
> +	int rv;
> +	u8 buf[I2C_SMBUS_BLOCK_MAX];
> +
> +	rv = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
> +	if (rv < 0)
> +		return rv;
> +
> +	if (rv == 8 && !strncmp(buf, "YM-2151E", strlen("YM-2151E")))
> +		return ym2151e;
> +	else if (rv == 8 && !strncmp(buf, "YH-5151E", strlen("YH-5151E")))
> +		return yh5151e;
> +
> +	dev_err(&client->dev, "Unsupported model %.*s\n", rv, buf);
> +	return -ENODEV;
> +}
> +
> +static const struct i2c_device_id fsp3y_id[] = {
> +	{"ym2151e", ym2151e},
> +	{"yh5151e", yh5151e}
> +};
> +
> +static int fsp3y_probe(struct i2c_client *client)
> +{
> +	struct fsp3y_data *data;
> +	const struct i2c_device_id *id;
> +	int rv;
> +
> +	data = devm_kzalloc(&client->dev, sizeof(struct fsp3y_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->chip = fsp3y_detect(client);

fsp3y_detect() can return an error which needs to be checked.
Easiest way would be to declare 'data->chip' as int and use

	data->chip = fsp3y_detect(client);
	if (data->chip < 0)
		return data->chip;

> +
> +	id = i2c_match_id(fsp3y_id, client);
> +	if (data->chip != id->driver_data)
> +		dev_warn(&client->dev,
> +			 "Device mismatch: Configured %s (%d), detected %d\n",
> +			 id->name,
> +			 (int)id->driver_data,
> +			 data->chip);

Please drop excessive continuation lines.

> +
> +	rv = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
> +	if (rv < 0)
> +		return rv;
> +	data->page = rv;
> +
> +	data->info = fsp3y_info[data->chip];
> +
> +	return pmbus_do_probe(client, &data->info);
> +}
> +
> +MODULE_DEVICE_TABLE(i2c, pmbus_id);
> +
> +/* This is the driver that will be inserted */
> +static struct i2c_driver fsp3y_driver = {
> +	.driver = {
> +		   .name = "fsp3y",
> +		   },
> +	.probe_new = fsp3y_probe,
> +	.id_table = fsp3y_id
> +};
> +
> +module_i2c_driver(fsp3y_driver);
> +
> +MODULE_AUTHOR("Václav Kubernát");
> +MODULE_DESCRIPTION("PMBus driver for FSP/3Y-Power power supplies");
> +MODULE_LICENSE("GPL");
> 

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