Re: [PATCH] STAGING:iio:light: fix ISL29018 init to handle brownout

[Jonathan Cameron <jic23@cam.ac.uk>]

On 08/09/11 23:18, Grant Grundler wrote:
> After a voltage brownout, sensor will now operate correctly.
>     
> Page 10 of ISL29018 data sheet and the Intersil Application Note 1534
> describe the required initialization sequence:
> 1. Write 0x00 to register 0x08 (TEST)
> 2. Write 0x00 to register 0x00 (CMD1)
> 3. msleep(1)
> 4. program remaining registers as before
> 
Nice clear comments.
> Signed-off-by: Grant Grundler <grundler@chromium.org>
> Reviewed-by: Bryan Freed <bfreed@chromium.org>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
> ---
> Change was tested on ARM/Nvidia Tegra2 (T25) machines.
> Diff below is against staging-2.6/staging-next.
> Please apply.
> 
> diff --git a/drivers/staging/iio/light/isl29018.c b/drivers/staging/iio/light/isl29018.c
> index 426b6af..da5bb33 100644
> --- a/drivers/staging/iio/light/isl29018.c
> +++ b/drivers/staging/iio/light/isl29018.c
> @@ -53,6 +53,10 @@
>  #define ISL29018_REG_ADD_DATA_MSB	0x03
>  #define ISL29018_MAX_REGS		ISL29018_REG_ADD_DATA_MSB
>  
> +#define ISL29018_REG_TEST		0x08
> +#define ISL29018_TEST_SHIFT		0
> +#define ISL29018_TEST_MASK		(0xFF << ISL29018_TEST_SHIFT)
> +
>  struct isl29018_chip {
>  	struct i2c_client	*client;
>  	struct mutex		lock;
> @@ -457,6 +461,48 @@ static int isl29018_chip_init(struct i2c_client *client)
>  
>  	memset(chip->reg_cache, 0, sizeof(chip->reg_cache));
>  
> +	/* Code added per Intersil Application Note 1534:
> +	 *     When VDD sinks to approximately 1.8V or below, some of
> +	 * the part's registers may change their state. When VDD
> +	 * recovers to 2.25V (or greater), the part may thus be in an
> +	 * unknown mode of operation. The user can return the part to
> +	 * a known mode of operation either by (a) setting VDD = 0V for
> +	 * 1 second or more and then powering back up with a slew rate
> +	 * of 0.5V/ms or greater, or (b) via I2C disable all ALS/PROX
> +	 * conversions, clear the test registers, and then rewrite all
> +	 * registers to the desired values.
> +	 * ...
> +	 * FOR ISL29011, ISL29018, ISL29021, ISL29023
> +	 * 1. Write 0x00 to register 0x08 (TEST)
> +	 * 2. Write 0x00 to register 0x00 (CMD1)
> +	 * 3. Rewrite all registers to the desired values
> +	 *
> +	 * ISL29018 Data Sheet (FN6619.1, Feb 11, 2010) essentially says
> +	 * the same thing EXCEPT the data sheet asks for a 1ms delay after
> +	 * writing the CMD1 register.
> +	 */
> +	status = isl29018_write_data(client, ISL29018_REG_TEST, 0,
> +				ISL29018_TEST_MASK, ISL29018_TEST_SHIFT);
> +	if (status < 0) {
> +		dev_err(&client->dev, "Failed to clear isl29018 TEST reg."
> +					"(%d)\n", status);
> +		return status;
> +	}
> +
> +	/* See Intersil AN1534 comments above.
> +	 * "Operating Mode" (COMMAND1) register is reprogrammed when
> +	 * data is read from the device.
> +	 */
> +	status = isl29018_write_data(client, ISL29018_REG_ADD_COMMAND1, 0,
> +				0xff, 0);
> +	if (status < 0) {
> +		dev_err(&client->dev, "Failed to clear isl29018 CMD1 reg."
> +					"(%d)\n", status);
> +		return status;
> +	}
> +
> +	msleep(1);	/* per data sheet, page 10 */
> +
>  	/* set defaults */
>  	status = isl29018_set_range(client, chip->range, &new_range);
>  	if (status < 0) {
>