Re: [PATCH v2] drivers: hwmon: max31827: Add PEC support
From: Guenter Roeck
Date: Fri May 24 2024 - 09:22:59 EST
On 5/24/24 00:00, Nuno Sá wrote:
On Thu, 2024-05-23 at 07:19 -0700, Guenter Roeck wrote:
On Thu, May 23, 2024 at 03:10:56PM +0300, Radu Sabau wrote:
Add support for PEC by attaching PEC attribute to the i2c device.
Add pec_store and pec_show function for accesing the "pec" file.
Signed-off-by: Radu Sabau <radu.sabau@xxxxxxxxxx>
---
Change log missing.
Documentation/hwmon/max31827.rst | 13 +++++--
drivers/hwmon/max31827.c | 64 ++++++++++++++++++++++++++++++++
2 files changed, 74 insertions(+), 3 deletions(-)
diff --git a/Documentation/hwmon/max31827.rst b/Documentation/hwmon/max31827.rst
index 44ab9dc064cb..9c11a9518c67 100644
--- a/Documentation/hwmon/max31827.rst
+++ b/Documentation/hwmon/max31827.rst
@@ -131,7 +131,14 @@ The Fault Queue bits select how many consecutive temperature
faults must occur
before overtemperature or undertemperature faults are indicated in the
corresponding status bits.
-Notes
------
+PEC Support
+-----------
+
+When reading a register value, the PEC byte is computed and sent by the chip.
+
+PEC on word data transaction respresents a signifcant increase in bandwitdh
+usage (+33% for both write and reads) in normal conditions.
-PEC is not implemented.
+Since this operation implies there will be an extra delay to each
+transaction, PEC can be disabled or enabled through sysfs.
+Just write 1 to the "pec" file for enabling PEC and 0 for disabling it.
diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index f8a13b30f100..e86f8890ee72 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -24,6 +24,7 @@
#define MAX31827_CONFIGURATION_1SHOT_MASK BIT(0)
#define MAX31827_CONFIGURATION_CNV_RATE_MASK GENMASK(3, 1)
+#define MAX31827_CONFIGURATION_PEC_EN_MASK BIT(4)
#define MAX31827_CONFIGURATION_TIMEOUT_MASK BIT(5)
#define MAX31827_CONFIGURATION_RESOLUTION_MASK GENMASK(7, 6)
#define MAX31827_CONFIGURATION_ALRM_POL_MASK BIT(8)
@@ -475,6 +476,54 @@ static ssize_t temp1_resolution_store(struct device *dev,
static DEVICE_ATTR_RW(temp1_resolution);
+static ssize_t pec_show(struct device *dev, struct device_attribute *devattr,
+ char *buf)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+
+ return scnprintf(buf, PAGE_SIZE, "%d\n", !!(client->flags &
I2C_CLIENT_PEC));
+}
+
+static ssize_t pec_store(struct device *dev, struct device_attribute *devattr,
+ const char *buf, size_t count)
+{
+ struct max31827_state *st = dev_get_drvdata(dev);
+ struct i2c_client *client = to_i2c_client(dev);
+ unsigned int val;
+ int err;
+
+ err = kstrtouint(buf, 10, &val);
+ if (err < 0)
+ return err;
+
+ switch (val) {
+ case 0:
+ err = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+ MAX31827_CONFIGURATION_PEC_EN_MASK,
+ val);
While correct, this is misleading. Should write 0.
+ if (err)
+ return err;
+
+ client->flags &= ~I2C_CLIENT_PEC;
+ break;
+ case 1:
+ err = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
+ MAX31827_CONFIGURATION_PEC_EN_MASK,
+ val);
This is wrong. s/val/MAX31827_CONFIGURATION_PEC_EN_MASK/
Then, maybe use regmap_set_bits()...
Good point, and regmap_clear_bits() above.
Guenter
- Nuno Sá