drivers/leds/leds-lp5523.c: adjust delays and add comments to them

Delays were little bit too long.  Adjust delay times and add some comments
to them.

Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
index 053e1f8..4248d78 100644 (file)
--- a/drivers/leds/leds-lp5523.c
+++ b/drivers/leds/leds-lp5523.c
@@ -205,11 +205,14 @@ static int lp5523_configure(struct i2c_client *client)
 
        lp5523_write(client, LP5523_REG_RESET, 0xff);
 
-       usleep_range(10000, 100000);
+       usleep_range(10000, 20000); /*
+                                    * Exact value is not available. 10 - 20ms
+                                    * appears to be enough for reset.
+                                    */
 
        ret |= lp5523_write(client, LP5523_REG_ENABLE, LP5523_ENABLE);
-       /* Chip startup time after reset is 500 us */
-       usleep_range(1000, 10000);
+       /* Chip startup time is 500 us, 1 - 2 ms gives some margin */
+       usleep_range(1000, 2000);
 
        ret |= lp5523_write(client, LP5523_REG_CONFIG,
                            LP5523_AUTO_INC | LP5523_PWR_SAVE |
@@ -246,8 +249,8 @@ static int lp5523_configure(struct i2c_client *client)
                return -1;
        }
 
-       /* Wait 3ms and check the engine status */
-       usleep_range(3000, 20000);
+       /* Let the programs run for couple of ms and check the engine status */
+       usleep_range(3000, 6000);
        lp5523_read(client, LP5523_REG_STATUS, &status);
        status &= LP5523_ENG_STATUS_MASK;
 
@@ -452,10 +455,10 @@ static ssize_t lp5523_selftest(struct device *dev,
        /* Measure VDD (i.e. VBAT) first (channel 16 corresponds to VDD) */
        lp5523_write(chip->client, LP5523_REG_LED_TEST_CTRL,
                                    LP5523_EN_LEDTEST | 16);
-       usleep_range(3000, 10000);
+       usleep_range(3000, 6000); /* ADC conversion time is typically 2.7 ms */
        ret = lp5523_read(chip->client, LP5523_REG_STATUS, &status);
        if (!(status & LP5523_LEDTEST_DONE))
-               usleep_range(3000, 10000);
+               usleep_range(3000, 6000); /* Was not ready. Wait little bit */
 
        ret |= lp5523_read(chip->client, LP5523_REG_LED_TEST_ADC, &vdd);
        vdd--;  /* There may be some fluctuation in measurement */
@@ -471,16 +474,16 @@ static ssize_t lp5523_selftest(struct device *dev,
                        chip->pdata->led_config[i].led_current);
 
                lp5523_write(chip->client, LP5523_REG_LED_PWM_BASE + i, 0xff);
-               /* let current stabilize 2ms before measurements start */
-               usleep_range(2000, 10000);
+               /* let current stabilize 2 - 4ms before measurements start */
+               usleep_range(2000, 4000);
                lp5523_write(chip->client,
                             LP5523_REG_LED_TEST_CTRL,
                             LP5523_EN_LEDTEST | i);
-               /* ledtest takes 2.7ms */
-               usleep_range(3000, 10000);
+               /* ADC conversion time is 2.7 ms typically */
+               usleep_range(3000, 6000);
                ret = lp5523_read(chip->client, LP5523_REG_STATUS, &status);
                if (!(status & LP5523_LEDTEST_DONE))
-                       usleep_range(3000, 10000);
+                       usleep_range(3000, 6000);/* Was not ready. Wait. */
                ret |= lp5523_read(chip->client, LP5523_REG_LED_TEST_ADC, &adc);
 
                if (adc >= vdd || adc < LP5523_ADC_SHORTCIRC_LIM)
@@ -933,9 +936,9 @@ static int lp5523_probe(struct i2c_client *client,
 
        if (pdata->enable) {
                pdata->enable(0);
-               usleep_range(1000, 10000);
+               usleep_range(1000, 2000); /* Keep enable down at least 1ms */
                pdata->enable(1);
-               usleep_range(1000, 10000); /* Spec says min 500us */
+               usleep_range(1000, 2000); /* 500us abs min. */
        }
 
        ret = lp5523_detect(client);