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

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

[Srinidhi KASAGAR]

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.

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>
---
 drivers/leds/leds-lp5521.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/drivers/leds/leds-lp5521.c b/drivers/leds/leds-lp5521.c
index 9fc122c..91a2928 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 +685,21 @@ 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
+	 * r channel current reg. This is a dummy read, otherwise
+	 * in some platforms, access to R G B channel program
+	 * execution mode to 'Run' in LP5521_REG_ENABLE register
+	 * will not have any affect - 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) {
-- 
1.7.4.3

RE: [PATCH] drivers/leds/leds-lp5521.c: check if reset is successful

[Srinidhi KASAGAR]

Richard,
Did you get a chance to look at this patch?

srinidhi

> -----Original Message-----
> From: Srinidhi KASAGAR
> Sent: Monday, October 10, 2011 5:00 PM
> To: rpurdie@rpsys.net
> Cc: linux-kernel@vger.kernel.org; linus.walleij@linaro.org; Srinidhi
> KASAGAR
> Subject: [PATCH] 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.
> 
> 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>
> ---
>  drivers/leds/leds-lp5521.c |   19 +++++++++++++++++++
>  1 files changed, 19 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/leds/leds-lp5521.c b/drivers/leds/leds-lp5521.c
> index 9fc122c..91a2928 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 +685,21 @@ 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
> +	 * r channel current reg. This is a dummy read, otherwise
> +	 * in some platforms, access to R G B channel program
> +	 * execution mode to 'Run' in LP5521_REG_ENABLE register
> +	 * will not have any affect - 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) {
> --
> 1.7.4.3

Re: [PATCH] drivers/leds/leds-lp5521.c: check if reset is successful

[Andrew Morton]

On Mon, 10 Oct 2011 17:00:02 +0530
Srinidhi KASAGAR <srinidhi.kasagar@stericsson.com> wrote:

> 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.
> 
> ...
>
> @@ -681,6 +685,21 @@ 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
> +	 * r channel current reg. This is a dummy read, otherwise
> +	 * in some platforms, access to R G B channel program
> +	 * execution mode to 'Run' in LP5521_REG_ENABLE register
> +	 * will not have any affect - 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);

Sorry, but I found that comment very hard to follow.

Is this version accurate and complete?

	/*
	 * Make sure that the chip is reset by reading back the r channel
	 * current reg. This 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!
	 */

RE: [PATCH] drivers/leds/leds-lp5521.c: check if reset is successful

[Srinidhi KASAGAR]

> -----Original Message-----
> From: Andrew Morton [mailto:akpm00@gmail.com] On Behalf Of Andrew
> Morton
> Sent: Wednesday, October 19, 2011 2:41 AM
> To: Srinidhi KASAGAR
> Cc: rpurdie@rpsys.net; linux-kernel@vger.kernel.org;
> linus.walleij@linaro.org
> Subject: Re: [PATCH] drivers/leds/leds-lp5521.c: check if reset is
> successful
> 
> On Mon, 10 Oct 2011 17:00:02 +0530
> Srinidhi KASAGAR <srinidhi.kasagar@stericsson.com> wrote:
> 
> > 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.
> >
> > ...
> >
> > @@ -681,6 +685,21 @@ 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
> > +	 * r channel current reg. This is a dummy read, otherwise
> > +	 * in some platforms, access to R G B channel program
> > +	 * execution mode to 'Run' in LP5521_REG_ENABLE register
> > +	 * will not have any affect - 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);
> 
> Sorry, but I found that comment very hard to follow.
> 
> Is this version accurate and complete?
> 
> 	/*
> 	 * Make sure that the chip is reset by reading back the r channel
> 	 * current reg. This 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!
> 	 */

That should be ok.

Thanks Andrew.

Srinidhi