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imx233: make button-lradc drive able to handle VDDIO derived values

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In most devices, the button ladder is not actually derived from VDDIO but
from a constant voltage source, making it very easy to read it. However on
some devices like ther ZEN X-Fi Style, the ladder is wired to VDDIO we
can be changed so it's crucial that the button driver correctly scales the
values wrt VDDIO.

Change-Id: Ifc11abe2838fa7d16d0d60ecd96964a8dc5ea6d7
This commit is contained in:
Amaury Pouly 2014-02-04 00:23:35 +01:00
parent 0e0c610df0
commit 0324bf59a8
4 changed files with 93 additions and 13 deletions
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19
firmware/target/arm/imx233/button-lradc-imx233.h
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@ -30,7 +30,19 @@
* - imx233_button_lradc_mapping: target-defined table of adc values and mapping
* - IMX233_BUTTON_LRADC_CHANNEL: lradc channel to use
* - IMX233_BUTTON_LRADC_HOLD_DET: define hold detection method (ignored if !HAS_BUTTON_HOLD)
* - IMX233_BUTTON_LRADC_MODE: define the button lradc mode
*
* The LRADC code supports two modes of operations: VDDIO relative or absolute.
* In the (default) absolute value mode, the LRADC channel is sampled and its value
* is compared to the one in the imx233_button_lradc_mapping table. This is
* appropriate when the resistor ladder is derived from a fixed voltage.
* In the VDDIO relative mode, the values in imx233_button_lradc_mapping are
* the values for a specific value of VDDIO which is given by
* IMX233_BUTTON_LRADC_VDDIO. In this mode, the code will also sample VDDIO
* and do the following comparison:
* lradc_value <=? imx233_button_lradc_mapping[i] * vddio_ref / vddio_value
* where vddio_ref is IMX233_BUTTON_LRADC_VDDIO.
*
* The available values of IMX233_BUTTON_LRADC_HOLD are:
* - BLH_ADC: detect hold using adc
* - BLH_EXT: target button driver implements imx233_button_lradc_hold() using
@ -40,6 +52,10 @@
* + BLH_GPIO_PIN: pin in bank
* + BLH_GPIO_INVERTED: define if inverted, default is active high
* + BLH_GPIO_PULLUP: define if pins needs pullup
*
* WARNING
* There must always be entry in imx233_button_lradc_mapping whose value is the steady
* value of the channel when no button is pressed, and which maps to no button (.btn = 0)
*/
/* hold detect method */
@ -74,5 +90,8 @@ int imx233_button_lradc_read(int others);
bool imx233_button_lradc_hold(void);
#endif
int imx233_button_lradc_read_raw(void); // return raw adc value
#ifdef IMX233_BUTTON_LRADC_VDDIO
int imx233_button_lradc_read_vddio(void);
#endif
#endif /* __button_lradc_imx233__ */