| Message ID | 20200910170821.1988467-1-linchuyuan@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | hwmon: pmbus: max20730: adjust the vout reading given voltage divider | expand |
On 9/10/20 10:08 AM, 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@google.com> > --- > drivers/hwmon/pmbus/max20730.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c > index c0bb05487e0e..4b56810fa894 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 +112,12 @@ 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) return ret; > + if (data->vout_voltage_divider[0] && data->vout_voltage_divider[1]) > + ret = DIV_ROUND_CLOSEST(ret * data->vout_voltage_divider[1], > + data->vout_voltage_divider[0]); With no range checks, ret * data->vout_voltage_divider[1] can easily overflow if vout_voltage_divider[] is larger than 0xffff. Also, the pmbus core does not expect register values larger than 0xffff (it typecasts the returned value explicitly to u16). [ Grumble. The PMBus specification has VOUT_SCALE commands to handle this situation. It is quite annoying that this chip does not support it. ] Guenter > + break; > default: > ret = -ENODATA; > break; > @@ -329,6 +336,15 @@ 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) >
diff --git a/drivers/hwmon/pmbus/max20730.c b/drivers/hwmon/pmbus/max20730.c index c0bb05487e0e..4b56810fa894 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 +112,12 @@ 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 (data->vout_voltage_divider[0] && data->vout_voltage_divider[1]) + ret = DIV_ROUND_CLOSEST(ret * data->vout_voltage_divider[1], + data->vout_voltage_divider[0]); + break; default: ret = -ENODATA; break; @@ -329,6 +336,15 @@ 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)
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@google.com> --- drivers/hwmon/pmbus/max20730.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)