From: Victor Duicu <victor.duicu@xxxxxxxxxxxxx>
This patch implements ACPI support to Microchip pac1921.
The driver can read shunt resistor value and label from ACPI table.
Signed-off-by: Victor Duicu <victor.duicu@xxxxxxxxxxxxx>
---
The patch was tested on minnowboard and sama5.
Differences related to previous versions:
v8:
- fix multiple coding style errors.
- in pac1921_match_acpi_device change error type to ENOMEM
at label is NULL branch.
- in pac1921_match_acpi_device when reading label,
change accesing method of string.
- change name of PAC1921_ACPI_GET_UOHMS_VALS to
PAC1921_ACPI_GET_uOHMS_VALS.
- add limits.h in include list.
- change integer constant in PAC1921_MAX_SHUNT_VALUE_OHMS
to INT_MAX / MICRO.
- change pac1921_shunt_is_invalid to pac1921_shunt_is_valid.
- in pac1921_match_acpi_device change name of variable rez to status.
v7:
- in pac1921_shunt_is_invalid remove brackets in return.
- in pac1921_match_acpi_device and pac1921_parse_of_fw move checking of
shunt value and scale calculation to pac1921_probe.
- in pac1921_match_acpi_device change devm_kmemdup to devm_kstrdup
and add label check for NULL.
- in pac1921_match_acpi_device and pac1921_parse_of_fw remove unnecessary
entry arguments. Now indio_dev is the only entry argument.
- in pac1921_probe, pac1921_match_acpi_device and pac1921_parse_of_fw
standardised structure accesing.
v6:
- set maximum acceptable value of shunt resistor to INT_MAX UOHMS
in devicetree, ACPI table and user input.
- in pac1921_match_acpi_device remove temp variable.
v5:
- set maximum acceptable value of shunt resistor to 2KOHM in devicetree,
ACPI table and user input. The chosen value is lesser than INT_MAX,
which is about 2.1KOHM.
- in pac1921_match_acpi_device and pac1921_parse_of_fw change to only
read 32b values for resistor shunt.
v4:
- change name of pac1921_shunt_is_valid to pac1921_shunt_is_invalid.
- fix coding style.
- in pac1921_parse_of_fw change back to device_property_read_u32.
v3:
- simplify and make inline function pac1921_shunt_is_valid. Make argument u64.
- fix link to DSM documentation.
- in pac1921_match_acpi_device and pac1921_parse_of_fw, the shunt value is
read as u64.
- in pac1921_parse_of_fw remove code for reading label value from
devicetree.
- in pac1921_write_shunt_resistor cast the multiply result to u64 in order
to fix overflow.
v2:
- remove name variable from priv. Driver reads label attribute with
sysfs.
- define pac1921_shunt_is_valid function.
- move default assignments in pac1921_probe to original position.
- roll back coding style changes.
- add documentation for DSM(the linked document was used as reference).
- remove acpi_match_device in pac1921_match_acpi_device.
- remove unnecessary null assignment and comment.
- change name of function pac1921_match_of_device to
pac1921_parse_of_fw.
v1:
- initial version for review.
drivers/iio/adc/pac1921.c | 98 +++++++++++++++++++++++++++++++++++----
1 file changed, 89 insertions(+), 9 deletions(-)
diff --git a/drivers/iio/adc/pac1921.c b/drivers/iio/adc/pac1921.c
index b0f6727cfe38..e24015390503 100644
--- a/drivers/iio/adc/pac1921.c
+++ b/drivers/iio/adc/pac1921.c
@@ -14,6 +14,7 @@
#include <linux/iio/triggered_buffer.h>
#include <linux/regmap.h>
#include <linux/units.h>
+#include <linux/limits.h>
/* pac1921 registers */
#define PAC1921_REG_GAIN_CFG 0x00
@@ -67,6 +68,12 @@ enum pac1921_mxsl {
#define PAC1921_DEFAULT_DI_GAIN 0 /* 2^(value): 1x gain (HW default) */
#define PAC1921_DEFAULT_NUM_SAMPLES 0 /* 2^(value): 1 sample (HW default) */
+#define PAC1921_ACPI_GET_uOHMS_VALS 0
+#define PAC1921_ACPI_GET_LABEL 1
+#define PAC1921_DSM_UUID "f7bb9932-86ee-4516-a236-7a7a742e55cb"
+/* The maximum accepted value of shunt_resistor in uOHMS <= INT_MAX */
+#define PAC1921_MAX_SHUNT_VALUE_OHMS (INT_MAX / MICRO)
+
/*
* Pre-computed scale factors for BUS voltage
* format: IIO_VAL_INT_PLUS_NANO
@@ -204,6 +211,11 @@ struct pac1921_priv {
} scan;
};
+static inline bool pac1921_shunt_is_valid(u32 shunt_val)
+{
+ return shunt_val > 0 && shunt_val <= INT_MAX;
+}
+
/*
* Check if first integration after configuration update has completed.
*
@@ -782,7 +794,7 @@ static ssize_t pac1921_write_shunt_resistor(struct iio_dev *indio_dev,
const char *buf, size_t len)
{
struct pac1921_priv *priv = iio_priv(indio_dev);
- u64 rshunt_uohm;
+ u32 rshunt_uohm;
int val, val_fract;
int ret;
@@ -793,8 +805,13 @@ static ssize_t pac1921_write_shunt_resistor(struct iio_dev *indio_dev,
if (ret)
return ret;
+ /* This check is to ensure val * MICRO won't overflow */
+ if (val > PAC1921_MAX_SHUNT_VALUE_OHMS)
+ return -EINVAL;
+
rshunt_uohm = val * MICRO + val_fract;
- if (rshunt_uohm == 0 || rshunt_uohm > INT_MAX)
+ /* This check is to ensure rshunt_uohm is non-zero positive */
+ if (!pac1921_shunt_is_valid(rshunt_uohm))
return -EINVAL;
guard(mutex)(&priv->lock);
@@ -1151,6 +1168,60 @@ static void pac1921_regulator_disable(void *data)
regulator_disable(regulator);
}
+/*
+ * Documentation related to the ACPI device definition
+ * https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ApplicationNotes/ApplicationNotes/PAC193X-Integration-Notes-for-Microsoft-Windows-10-and-Windows-11-Driver-Support-DS00002534.pdf
+ */
+static int pac1921_match_acpi_device(struct iio_dev *indio_dev)
+{
+ acpi_handle handle;
+ union acpi_object *status;
+ guid_t guid;
+ char *label;
+ struct pac1921_priv *priv = iio_priv(indio_dev);
+ struct device *dev = &priv->client->dev;
+
+ guid_parse(PAC1921_DSM_UUID, &guid);
+ handle = ACPI_HANDLE(dev);
+
+ status = acpi_evaluate_dsm(handle, &guid, 1, PAC1921_ACPI_GET_uOHMS_VALS, NULL);
+ if (!status)
+ return dev_err_probe(dev, -EINVAL,
+ "Could not read shunt from ACPI table\n");
+
+ priv->rshunt_uohm = status->package.elements[0].integer.value;
+ ACPI_FREE(status);
+
+ status = acpi_evaluate_dsm(handle, &guid, 1, PAC1921_ACPI_GET_LABEL, NULL);
+ if (!status)
+ return dev_err_probe(dev, -EINVAL,
+ "Could not read label from ACPI table\n");
+
+ label = devm_kstrdup(dev, status->package.elements[0].string.pointer, GFP_KERNEL);
+ if (!label)
+ return -ENOMEM;
+
+ indio_dev->label = label;
+ ACPI_FREE(status);
+
+ return 0;
+}
+
+static int pac1921_parse_of_fw(struct iio_dev *indio_dev)
+{
+ int ret;
+ struct pac1921_priv *priv = iio_priv(indio_dev);
+ struct device *dev = &priv->client->dev;
+
+ ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
+ &priv->rshunt_uohm);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "Cannot read shunt resistor property\n");
+
+ return 0;
+}
+
static int pac1921_probe(struct i2c_client *client)
{
struct device *dev = &client->dev;
@@ -1179,14 +1250,16 @@ static int pac1921_probe(struct i2c_client *client)
priv->di_gain = PAC1921_DEFAULT_DI_GAIN;
priv->n_samples = PAC1921_DEFAULT_NUM_SAMPLES;
- ret = device_property_read_u32(dev, "shunt-resistor-micro-ohms",
- &priv->rshunt_uohm);
- if (ret)
+ if (ACPI_HANDLE(dev))
+ ret = pac1921_match_acpi_device(indio_dev);
+ else
+ ret = pac1921_parse_of_fw(indio_dev);
+ if (ret < 0)
return dev_err_probe(dev, ret,
- "Cannot read shunt resistor property\n");
- if (priv->rshunt_uohm == 0 || priv->rshunt_uohm > INT_MAX)
- return dev_err_probe(dev, -EINVAL,
- "Invalid shunt resistor: %u\n",
+ "Parameter parsing error\n");
+
+ if (!pac1921_shunt_is_valid(priv->rshunt_uohm))
+ return dev_err_probe(dev, -EINVAL, "Invalid shunt resistor: %u\n",
priv->rshunt_uohm);
pac1921_calc_current_scales(priv);
@@ -1246,11 +1319,18 @@ static const struct of_device_id pac1921_of_match[] = {
};
MODULE_DEVICE_TABLE(of, pac1921_of_match);
+static const struct acpi_device_id pac1921_acpi_match[] = {
+ { "MCHP1921" },
+ { }
+};
+MODULE_DEVICE_TABLE(acpi, pac1921_acpi_match);
+
static struct i2c_driver pac1921_driver = {
.driver = {
.name = "pac1921",
.pm = pm_sleep_ptr(&pac1921_pm_ops),
.of_match_table = pac1921_of_match,
+ .acpi_match_table = pac1921_acpi_match,
},
.probe = pac1921_probe,
.id_table = pac1921_id,
base-commit: 6415477ba63dea58b5cbf9ddcae75f18f33c71a4
--
2.43.0
