[PATCH 3/5] hwmon: (tmp102) Improve handling of initial read delay

Guenter Roeck
2016-06-24T00:28:58Z

If the chip was in shutdown mode when the driver was loaded, the first
conversion is ready no more than 35 milli-seconds after the chip was
taken out of shutdown. The driver delay was so far set to 333 ms (HZ / 3),
which is much higher than the maximum time needed by the chip.

Reduce the time to 35 milli-seconds. Instead of returning -EAGAIN if data
is not yet available, go to sleep for the remaining time.

Introduce a 'valid' flag to ensure that sensor data is actually read
even if requested less than 333 ms after the driver was loaded.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
drivers/hwmon/tmp102.c | 44 ++++++++++++++++++++++++++++----------------
1 file changed, 28 insertions(+), 16 deletions(-)

diff --git a/drivers/hwmon/tmp102.c b/drivers/hwmon/tmp102.c
index 5bdf262e6a0e..615f9c176aaf 100644
--- a/drivers/hwmon/tmp102.c
+++ b/drivers/hwmon/tmp102.c
@@ -13,6 +13,7 @@
* GNU General Public License for more details.
*/

+#include <linux/delay.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
@@ -46,13 +47,16 @@
#define TMP102_TLOW_REG 0x02
#define TMP102_THIGH_REG 0x03

+#define CONVERSION_TIME_MS 35 /* in milli-seconds */
+
struct tmp102 {
struct i2c_client *client;
struct mutex lock;
u16 config_orig;
unsigned long last_update;
+ unsigned long ready_time;
+ bool valid;
int temp[3];
- bool first_time;
};

/* convert left adjusted 13-bit TMP102 register value to milliCelsius */
@@ -78,8 +82,16 @@ static struct tmp102 *tmp102_update_device(struct device *dev)
struct tmp102 *tmp102 = dev_get_drvdata(dev);
struct i2c_client *client = tmp102->client;

+ /* Is it too early to return a conversion ? */
+ if (time_before(jiffies, tmp102->ready_time)) {
+ unsigned long sleeptime = tmp102->ready_time - jiffies;
+
+ msleep(jiffies_to_msecs(sleeptime));
+ }
+
mutex_lock(&tmp102->lock);
- if (time_after(jiffies, tmp102->last_update + HZ / 3)) {
+ if (!tmp102->valid ||
+ time_after(jiffies, tmp102->last_update + HZ / 3)) {
int i;
for (i = 0; i < ARRAY_SIZE(tmp102->temp); ++i) {
int status = i2c_smbus_read_word_swapped(client,
@@ -88,7 +100,7 @@ static struct tmp102 *tmp102_update_device(struct device *dev)
tmp102->temp[i] = tmp102_reg_to_mC(status);
}
tmp102->last_update = jiffies;
- tmp102->first_time = false;
+ tmp102->valid = true;
}
mutex_unlock(&tmp102->lock);
return tmp102;
@@ -98,12 +110,6 @@ static int tmp102_read_temp(void *dev, int *temp)
{
struct tmp102 *tmp102 = tmp102_update_device(dev);

- /* Is it too early even to return a conversion? */
- if (tmp102->first_time) {
- dev_dbg(dev, "%s: Conversion not ready yet..\n", __func__);
- return -EAGAIN;
- }
-
*temp = tmp102->temp[0];

return 0;
@@ -116,10 +122,6 @@ static ssize_t tmp102_show_temp(struct device *dev,
struct sensor_device_attribute *sda = to_sensor_dev_attr(attr);
struct tmp102 *tmp102 = tmp102_update_device(dev);

- /* Is it too early even to return a read? */
- if (tmp102->first_time)
- return -EAGAIN;
-
return sprintf(buf, "%d\n", tmp102->temp[sda->index]);
}

@@ -224,11 +226,18 @@ static int tmp102_probe(struct i2c_client *client,
dev_err(dev, "config settings did not stick\n");
return -ENODEV;
}
- tmp102->last_update = jiffies;
- /* Mark that we are not ready with data until conversion is complete */
- tmp102->first_time = true;
+
mutex_init(&tmp102->lock);

+ tmp102->ready_time = jiffies;
+ if (tmp102->config_orig & TMP102_CONF_SD) {
+ /*
+ * Mark that we are not ready with data until the first
+ * conversion is complete
+ */
+ tmp102->ready_time += msecs_to_jiffies(CONVERSION_TIME_MS);
+ }
+
hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
tmp102,
tmp102_groups);
@@ -261,12 +270,15 @@ static int tmp102_suspend(struct device *dev)
static int tmp102_resume(struct device *dev)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct tmp102 *tmp102 = i2c_get_clientdata(client);
int config;

config = i2c_smbus_read_word_swapped(client, TMP102_CONF_REG);
if (config < 0)
return config;

+ tmp102->ready_time = jiffies + msecs_to_jiffies(CONVERSION_TIME_MS);
+
config &= ~TMP102_CONF_SD;
return i2c_smbus_write_word_swapped(client, TMP102_CONF_REG, config);
}
--
2.5.0