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    Subject[PATCH v3 1/3] hwmon: (tmp102) Improve handling of initial read delay
    Date
    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.

    Signed-off-by: Guenter Roeck <linux@roeck-us.net>
    ---
    v3: Don't go to sleep if sensor readings are not available;
    instead, return -EAGAIN (matching previous behavior)
    tmp102_update_device() is now a void function.
    v2: No change

    Note: This series depends on the following two patches in -next.

    hwmon: (tmp102) Drop FSF address
    hwmon: (tmp102) Use devm_add_action to register cleanup function

    drivers/hwmon/tmp102.c | 44 ++++++++++++++++++++++++++++++--------------
    1 file 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);
    }
    --
    2.5.0
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