hwmon: (tmp102) Improve handling of initial read delay

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.

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

Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 30 insertions, 14 deletions

diff --git a/drivers/hwmon/tmp102.c b/drivers/hwmon/tmp102.c
index 5bdf262e6a0e..fd4a4515692a 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 */
@@ -73,13 +77,14 @@ static const u8 tmp102_reg[] = {
         TMP102_THIGH_REG,
 };
 
-static struct tmp102 *tmp102_update_device(struct device *dev)
+static void tmp102_update_device(struct device *dev)
 {
         struct tmp102 *tmp102 = dev_get_drvdata(dev);
         struct i2c_client *client = tmp102->client;
 
         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,
@@ -88,22 +93,22 @@ 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;
 }
 
 static int tmp102_read_temp(void *dev, int *temp)
 {
-        struct tmp102 *tmp102 = tmp102_update_device(dev);
+        struct tmp102 *tmp102 = dev_get_drvdata(dev);
 
-        /* Is it too early even to return a conversion? */
-        if (tmp102->first_time) {
+        if (time_before(jiffies, tmp102->ready_time)) {
                 dev_dbg(dev, "%s: Conversion not ready yet..\n", __func__);
                 return -EAGAIN;
         }
 
+        tmp102_update_device(dev);
+
         *temp = tmp102->temp[0];
 
         return 0;
@@ -114,12 +119,13 @@ static ssize_t tmp102_show_temp(struct device *dev,
                                 char *buf)
 {
         struct sensor_device_attribute *sda = to_sensor_dev_attr(attr);
-        struct tmp102 *tmp102 = tmp102_update_device(dev);
+        struct tmp102 *tmp102 = dev_get_drvdata(dev);
 
-        /* Is it too early even to return a read? */
-        if (tmp102->first_time)
+        if (time_before(jiffies, tmp102->ready_time))
                 return -EAGAIN;
 
+        tmp102_update_device(dev);
+
         return sprintf(buf, "%d\n", tmp102->temp[sda->index]);
 }
 
@@ -224,11 +230,18 @@ 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 +274,15 @@ 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);
 }