drivers/leds/leds-lp5521.c: check if reset is successful

Make sure that the reset is successful by issuing a dummy read to R
channel current register and check its default value.  On some platforms,
without this dummy read, any further access to {R/G/B}_EXEC will not have
any impact.

[akpm@linux-foundation.org: fix up code comment]
Signed-off-by: srinidhi kasagar <srinidhi.kasagar@stericsson.com>
Tested-by: Naga Radhesh <naga.radheshy@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/leds/leds-lp5521.c b/drivers/leds/leds-lp5521.c
index 16f281b8c2d0..cb641f1b3342 100644
--- a/drivers/leds/leds-lp5521.c
+++ b/drivers/leds/leds-lp5521.c
@@ -97,6 +97,9 @@
 /* Status */
 #define LP5521_EXT_CLK_USED             0x08
 
+/* default R channel current register value */
+#define LP5521_REG_R_CURR_DEFAULT       0xAF
+
 struct lp5521_engine {
         int             id;
         u8              mode;
@@ -643,6 +646,7 @@ static int __devinit lp5521_probe(struct i2c_client *client,
         struct lp5521_chip              *chip;
         struct lp5521_platform_data     *pdata;
         int ret, i, led;
+        u8 buf;
 
         chip = kzalloc(sizeof(*chip), GFP_KERNEL);
         if (!chip)
@@ -681,6 +685,20 @@ static int __devinit lp5521_probe(struct i2c_client *client,
                                      * Exact value is not available. 10 - 20ms
                                      * appears to be enough for reset.
                                      */
+
+        /*
+         * Make sure that the chip is reset by reading back the r channel
+         * current reg. This is dummy read is required on some platforms -
+         * otherwise further access to the R G B channels in the
+         * LP5521_REG_ENABLE register will not have any effect - strange!
+         */
+        lp5521_read(client, LP5521_REG_R_CURRENT, &buf);
+        if (buf != LP5521_REG_R_CURR_DEFAULT) {
+                dev_err(&client->dev, "error in reseting chip\n");
+                goto fail2;
+        }
+        usleep_range(10000, 20000);
+
         ret = lp5521_detect(client);
 
         if (ret) {