diff mbox series

[1/2] hwmon: pmbus: Add support for ltc2971

Message ID 20241026-add-ltc2971-v1-1-109ec21687bc@gmail.com (mailing list archive)
State Changes Requested
Headers show
Series Add support for LTC2971 power manager | expand

Commit Message

Patryk Oct. 26, 2024, 9:08 a.m. UTC 
LTC2971 is a power manager similar to already supported LTC2972,
it uses the same register set but supports a different voltage range.

Signed-off-by: Patryk Biel <pbiel7@gmail.com>
---
 drivers/hwmon/pmbus/ltc2978.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

Comments

Guenter Roeck Oct. 26, 2024, 4:18 p.m. UTC | #1 
On 10/26/24 02:08, Patryk Biel wrote:
> LTC2971 is a power manager similar to already supported LTC2972,
> it uses the same register set but supports a different voltage range.
> 
> Signed-off-by: Patryk Biel <pbiel7@gmail.com>
> ---
>   drivers/hwmon/pmbus/ltc2978.c | 34 +++++++++++++++++++++++++++++++---

Please also update Documentation/hwmon/ltc2978.rst and drivers/hwmon/pmbus/Kconfig.

>   1 file changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/ltc2978.c b/drivers/hwmon/pmbus/ltc2978.c
> index 73a86f4d647288be97615f19a5c6314e4036e6a3..681e7b811dbcc263fe8f5e4f9da30fcbc7e019ad 100644
> --- a/drivers/hwmon/pmbus/ltc2978.c
> +++ b/drivers/hwmon/pmbus/ltc2978.c
> @@ -21,7 +21,8 @@
>   
>   enum chips {
>   	/* Managers */
> -	ltc2972, ltc2974, ltc2975, ltc2977, ltc2978, ltc2979, ltc2980,
> +	ltc2971, ltc2972, ltc2974, ltc2975, ltc2977, ltc2978,
> +	ltc2979, ltc2980,
>   	/* Controllers */
>   	ltc3880, ltc3882, ltc3883, ltc3884, ltc3886, ltc3887, ltc3889, ltc7132, ltc7880,
>   	/* Modules */
> @@ -61,6 +62,7 @@ enum chips {
>   
>   #define LTC2978_ID_MASK			0xfff0
>   
> +#define LTC2971_ID			0x0320
>   #define LTC2972_ID			0x0310
>   #define LTC2974_ID			0x0210
>   #define LTC2975_ID			0x0220
> @@ -533,6 +535,7 @@ static int ltc2978_write_word_data(struct i2c_client *client, int page,
>   }
>   
>   static const struct i2c_device_id ltc2978_id[] = {
> +	{"ltc2971", ltc2971},
>   	{"ltc2972", ltc2972},
>   	{"ltc2974", ltc2974},
>   	{"ltc2975", ltc2975},
> @@ -564,11 +567,19 @@ MODULE_DEVICE_TABLE(i2c, ltc2978_id);
>   
>   #if IS_ENABLED(CONFIG_SENSORS_LTC2978_REGULATOR)
>   #define LTC2978_ADC_RES	0xFFFF
> +#define LTC2978_UV_STEP	1000
> +
> +/* Common for most chips */
>   #define LTC2978_N_ADC	122
>   #define LTC2978_MAX_UV	(LTC2978_ADC_RES * LTC2978_N_ADC)
> -#define LTC2978_UV_STEP	1000
>   #define LTC2978_N_VOLTAGES	((LTC2978_MAX_UV / LTC2978_UV_STEP) + 1)
>   

Please just add the chip specific defines as you do below, and don't move
the defines above around. It happens a lot that there are common definitions
followed by chip specific ones. Spelling that out explicitly doesn't really
add much if any value and just results in rearranged code whenever a new
chip with other parameters is added.

> +/* LTC2971 */
> +#define LTC2971_N_ADC	4500
> +#define LTC2971_MAX_UV	(LTC2978_ADC_RES * LTC2971_N_ADC)

I think something is wrong here.

4500 * 65535 uV ~= 295V.

However, the datasheet says that the output voltage is calculated by
(register value / 1024), where the register value is a 16-bit value.
65535 / 1024 ~= 64V. Where does the 4,500 come from ?

> +#define LTC2971_N_VOLTAGES	((LTC2971_MAX_UV / LTC2978_UV_STEP) + 1)

Does the chip really support 294,908 voltages ? That seems impossible since
the VOUT_COMMAND register is only 16 bit wide.

Unless I misunderstand the datasheet, the voltage resolution should be 1/1024V
or 976 uV, and there should be 65,536 voltages. This is from the chip datasheet,
PMBus Command Description, Note 1: Data Formats, for L16 data.

If my understanding is wrong, please explain and document your numbers.

Thanks,
Guenter
Patryk Oct. 27, 2024, 10:52 a.m. UTC | #2 
Hi,
> Unless I misunderstand the datasheet, the voltage resolution should be 1/1024V
> or 976 uV, and there should be 65,536 voltages. This is from the chip datasheet,
> PMBus Command Description, Note 1: Data Formats, for L16 data.
I really screwed up, I took 4500 (N_ADC 4.5 mV) from datasheet from
ADC characteristics section and mistakenly interpreted it as the
voltage resolution. Should've spent more time on this, please
disregard this patch series and I apologize for the hassle.

Best regards,
Patryk
diff mbox series

Patch

diff --git a/drivers/hwmon/pmbus/ltc2978.c b/drivers/hwmon/pmbus/ltc2978.c
index 73a86f4d647288be97615f19a5c6314e4036e6a3..681e7b811dbcc263fe8f5e4f9da30fcbc7e019ad 100644
--- a/drivers/hwmon/pmbus/ltc2978.c
+++ b/drivers/hwmon/pmbus/ltc2978.c
@@ -21,7 +21,8 @@ 
 
 enum chips {
 	/* Managers */
-	ltc2972, ltc2974, ltc2975, ltc2977, ltc2978, ltc2979, ltc2980,
+	ltc2971, ltc2972, ltc2974, ltc2975, ltc2977, ltc2978,
+	ltc2979, ltc2980,
 	/* Controllers */
 	ltc3880, ltc3882, ltc3883, ltc3884, ltc3886, ltc3887, ltc3889, ltc7132, ltc7880,
 	/* Modules */
@@ -61,6 +62,7 @@  enum chips {
 
 #define LTC2978_ID_MASK			0xfff0
 
+#define LTC2971_ID			0x0320
 #define LTC2972_ID			0x0310
 #define LTC2974_ID			0x0210
 #define LTC2975_ID			0x0220
@@ -533,6 +535,7 @@  static int ltc2978_write_word_data(struct i2c_client *client, int page,
 }
 
 static const struct i2c_device_id ltc2978_id[] = {
+	{"ltc2971", ltc2971},
 	{"ltc2972", ltc2972},
 	{"ltc2974", ltc2974},
 	{"ltc2975", ltc2975},
@@ -564,11 +567,19 @@  MODULE_DEVICE_TABLE(i2c, ltc2978_id);
 
 #if IS_ENABLED(CONFIG_SENSORS_LTC2978_REGULATOR)
 #define LTC2978_ADC_RES	0xFFFF
+#define LTC2978_UV_STEP	1000
+
+/* Common for most chips */
 #define LTC2978_N_ADC	122
 #define LTC2978_MAX_UV	(LTC2978_ADC_RES * LTC2978_N_ADC)
-#define LTC2978_UV_STEP	1000
 #define LTC2978_N_VOLTAGES	((LTC2978_MAX_UV / LTC2978_UV_STEP) + 1)
 
+/* LTC2971 */
+#define LTC2971_N_ADC	4500
+#define LTC2971_MAX_UV	(LTC2978_ADC_RES * LTC2971_N_ADC)
+#define LTC2971_N_VOLTAGES	((LTC2971_MAX_UV / LTC2978_UV_STEP) + 1)
+
+/* Common for most chips */
 static const struct regulator_desc ltc2978_reg_desc[] = {
 	PMBUS_REGULATOR_STEP("vout", 0, LTC2978_N_VOLTAGES, LTC2978_UV_STEP, 0),
 	PMBUS_REGULATOR_STEP("vout", 1, LTC2978_N_VOLTAGES, LTC2978_UV_STEP, 0),
@@ -580,6 +591,12 @@  static const struct regulator_desc ltc2978_reg_desc[] = {
 	PMBUS_REGULATOR_STEP("vout", 7, LTC2978_N_VOLTAGES, LTC2978_UV_STEP, 0),
 };
 
+/* LTC2971 */
+static const struct regulator_desc ltc2971_reg_desc[] = {
+	PMBUS_REGULATOR_STEP("vout", 0, LTC2971_N_VOLTAGES, LTC2978_UV_STEP, 0),
+	PMBUS_REGULATOR_STEP("vout", 1, LTC2971_N_VOLTAGES, LTC2978_UV_STEP, 0),
+};
+
 static const struct regulator_desc ltc2978_reg_desc_default[] = {
 	PMBUS_REGULATOR("vout", 0),
 	PMBUS_REGULATOR("vout", 1),
@@ -624,7 +641,9 @@  static int ltc2978_get_id(struct i2c_client *client)
 
 	chip_id &= LTC2978_ID_MASK;
 
-	if (chip_id == LTC2972_ID)
+	if (chip_id == LTC2971_ID)
+		return ltc2971;
+	else if (chip_id == LTC2972_ID)
 		return ltc2972;
 	else if (chip_id == LTC2974_ID)
 		return ltc2974;
@@ -731,6 +750,7 @@  static int ltc2978_probe(struct i2c_client *client)
 	data->temp2_max = 0x7c00;
 
 	switch (data->id) {
+	case ltc2971:
 	case ltc2972:
 		info->read_word_data = ltc2975_read_word_data;
 		info->pages = LTC2972_NUM_PAGES;
@@ -861,6 +881,13 @@  static int ltc2978_probe(struct i2c_client *client)
 #if IS_ENABLED(CONFIG_SENSORS_LTC2978_REGULATOR)
 	info->num_regulators = info->pages;
 	switch (data->id) {
+	case ltc2971:
+		info->reg_desc = ltc2971_reg_desc;
+		if (info->num_regulators > ARRAY_SIZE(ltc2971_reg_desc)) {
+			dev_warn(&client->dev, "num_regulators too large!");
+			info->num_regulators = ARRAY_SIZE(ltc2971_reg_desc);
+		}
+		break;
 	case ltc2972:
 	case ltc2974:
 	case ltc2975:
@@ -892,6 +919,7 @@  static int ltc2978_probe(struct i2c_client *client)
 
 #ifdef CONFIG_OF
 static const struct of_device_id ltc2978_of_match[] = {
+	{ .compatible = "lltc,ltc2971" },
 	{ .compatible = "lltc,ltc2972" },
 	{ .compatible = "lltc,ltc2974" },
 	{ .compatible = "lltc,ltc2975" },