On 9/10/20 5:00 PM, Chu Lin wrote:
> Problem:
> We use voltage dividers so that the voltage presented at the voltage
> sense pins is confusing. We might need to convert these readings to more
> meaningful readings given the voltage divider.
>
> Solution:
> Read the voltage divider resistance from dts and convert the voltage
> reading to a more meaningful reading.
>
> Testing:
> max20730 with voltage divider
>
> Signed-off-by: Chu Lin <linchuyuan@xxxxxxxxxx>
For my reference:
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
We'll have to wait for DT review before I can apply the patch.
Thanks,
Guenter
> ---
> ChangeLog v1 -> v2
> - Don't do anything to the ret if an error is returned from
> pmbus_read_word
> - avoid overflow when doing multiplication
>
> drivers/hwmon/pmbus/max20730.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c
> index c0bb05487e0e..83affdad4060 100644
> --- a/drivers/hwmon/pmbus/max20730.c
> +++ b/drivers/hwmon/pmbus/max20730.c
> @@ -29,6 +29,7 @@ struct max20730_data {
> struct pmbus_driver_info info;
> struct mutex lock; /* Used to protect against parallel writes */
> u16 mfr_devset1;
> + u32 vout_voltage_divider[2];
> };
>
> #define to_max20730_data(x) container_of(x, struct max20730_data, info)
> @@ -111,6 +112,14 @@ static int max20730_read_word_data(struct i2c_client *client, int page,
> max_c = max_current[data->id][(data->mfr_devset1 >> 5) & 0x3];
> ret = val_to_direct(max_c, PSC_CURRENT_OUT, info);
> break;
> + case PMBUS_READ_VOUT:
> + ret = pmbus_read_word_data(client, page, phase, reg);
> + if (ret > 0 && data->vout_voltage_divider[0] && data->vout_voltage_divider[1]) {
> + u64 temp = DIV_ROUND_CLOSEST_ULL((u64)ret * data->vout_voltage_divider[1],
> + data->vout_voltage_divider[0]);
> + ret = clamp_val(temp, 0, 0xffff);
> + }
> + break;
> default:
> ret = -ENODATA;
> break;
> @@ -329,6 +338,15 @@ static int max20730_probe(struct i2c_client *client,
> data->id = chip_id;
> mutex_init(&data->lock);
> memcpy(&data->info, &max20730_info[chip_id], sizeof(data->info));
> + if (of_property_read_u32_array(client->dev.of_node, "vout-voltage-divider",
> + data->vout_voltage_divider,
> + ARRAY_SIZE(data->vout_voltage_divider)) != 0)
> + memset(data->vout_voltage_divider, 0, sizeof(data->vout_voltage_divider));
> + if (data->vout_voltage_divider[1] < data->vout_voltage_divider[0]) {
> + dev_err(dev,
> + "The total resistance of voltage divider is less than output resistance\n");
> + return -ENODEV;
> + }
>
> ret = i2c_smbus_read_word_data(client, MAX20730_MFR_DEVSET1);
> if (ret < 0)
>
