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

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

firmware/target/arm/imx233/button-lradc-imx233.c

@@ -58,6 +58,10 @@
 /* delay's delay */
 #define DELAY   (LRADC_DELAY_FREQ / RATE / SAMPLES)
 
+#ifdef IMX233_BUTTON_LRADC_VDDIO
+#define HAS_VDDIO
+#endif
+
 static int button_delay;
 static int button_chan;
 static int button_val[2];
@@ -65,9 +69,18 @@ static int button_idx;
 static int button_mask;
 static int table_size;
 static int raw_val;
+#ifdef HAS_VDDIO
+static int vddio_chan;
+static int vddio_val;
+#endif
+static int delay_chan_mask; // trigger channel mask
+static int irq_chan_mask; // triggered channel mask
 
 static int button_find(int val)
 {
+#ifdef IMX233_BUTTON_LRADC_VDDIO
+        val = (val * IMX233_BUTTON_LRADC_VDDIO) / vddio_val;
+#endif
     // shortcuts
     struct imx233_button_lradc_mapping_t *table = imx233_button_lradc_mapping;
     /* FIXME use a dichotomy */
@@ -91,18 +104,35 @@ static int button_find(int val)
 
 static void button_lradc_irq(int chan)
 {
-    (void) chan;
+    /* read value, clear channel */
-    /* read value, kick channel */
+#ifdef HAS_VDDIO
-    raw_val = imx233_lradc_read_channel(button_chan) / SAMPLES;
+    if(chan == vddio_chan)
-    imx233_lradc_clear_channel(button_chan);
+    {
-    imx233_lradc_setup_channel(button_chan, true, true, SAMPLES - 1, LRADC_SRC(CHAN));
+        vddio_val = imx233_lradc_read_channel(vddio_chan) / SAMPLES;
-    imx233_lradc_setup_delay(button_delay, 1 << button_chan, 0, SAMPLES - 1, DELAY);
+        vddio_val *= 2; /* VDDIO channel has internal divider */
-    imx233_lradc_kick_delay(button_delay);
+        imx233_lradc_clear_channel(vddio_chan);
-    /* compute mask, compare to previous one */
+        imx233_lradc_setup_channel(vddio_chan, true, true, SAMPLES - 1, LRADC_SRC_VDDIO);
-    button_val[button_idx] = button_find(raw_val);
+    }
-    button_idx = 1 - button_idx;
+#endif
-    if(button_val[0] == button_val[1])
+    if(chan == button_chan)
-        button_mask = button_val[0];
+    {
+        raw_val = imx233_lradc_read_channel(button_chan) / SAMPLES;
+        imx233_lradc_clear_channel(button_chan);
+        imx233_lradc_setup_channel(button_chan, true, true, SAMPLES - 1, LRADC_SRC(CHAN));
+    }
+    /* record irq, trigger delay if all IRQs have been fired */
+    irq_chan_mask |= 1 << chan;
+    if(irq_chan_mask == delay_chan_mask)
+    {
+        irq_chan_mask = 0;
+        imx233_lradc_setup_delay(button_delay, delay_chan_mask, 0, SAMPLES - 1, DELAY);
+        imx233_lradc_kick_delay(button_delay);
+        /* compute mask, compare to previous one */
+        button_val[button_idx] = button_find(raw_val);
+        button_idx = 1 - button_idx;
+        if(button_val[0] == button_val[1])
+            button_mask = button_val[0];
+    }
 }
 
 void imx233_button_lradc_init(void)
@@ -118,9 +148,19 @@ void imx233_button_lradc_init(void)
     if(button_delay < 0)
         panicf("Cannot get delay for button-lradc");
     imx233_lradc_setup_channel(button_chan, true, true, SAMPLES - 1, LRADC_SRC(CHAN));
-    imx233_lradc_setup_delay(button_delay, 1 << button_chan, 0, SAMPLES - 1, DELAY);
     imx233_lradc_enable_channel_irq(button_chan, true);
     imx233_lradc_set_channel_irq_callback(button_chan, button_lradc_irq);
+    delay_chan_mask = 1 << button_chan;
+#ifdef HAS_VDDIO
+    vddio_chan = imx233_lradc_acquire_channel(LRADC_SRC_VDDIO, TIMEOUT_NOBLOCK);
+    if(vddio_chan < 0)
+        panicf("Cannot get vddio channel for button-lradc");
+    imx233_lradc_setup_channel(vddio_chan, true, true, SAMPLES - 1, LRADC_SRC_VDDIO);
+    imx233_lradc_enable_channel_irq(vddio_chan, true);
+    imx233_lradc_set_channel_irq_callback(vddio_chan, button_lradc_irq);
+    delay_chan_mask |= 1 << vddio_chan;
+#endif
+    imx233_lradc_setup_delay(button_delay, delay_chan_mask, 0, SAMPLES - 1, DELAY);
     imx233_lradc_kick_delay(button_delay);
 #if defined(HAS_BUTTON_HOLD) && IMX233_BUTTON_LRADC_HOLD_DET == BLH_GPIO
     imx233_pinctrl_acquire(BLH_GPIO_BANK, BLH_GPIO_PIN, "button_lradc_hold");
@@ -164,3 +204,10 @@ int imx233_button_lradc_read_raw(void)
 {
     return raw_val;
 }
+
+#ifdef HAS_VDDIO
+int imx233_button_lradc_read_vddio(void)
+{
+    return vddio_val; // the VDDIO channel has an internal divider
+}
+#endif

firmware/target/arm/imx233/button-lradc-imx233.h

@@ -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__ */

firmware/target/arm/imx233/creative-zen/button-target.h

@@ -25,11 +25,22 @@
 
 bool button_debug_screen(void);
 
+/* HOLD button */
 #if !defined(CREATIVE_ZENXFISTYLE)
 #define HAS_BUTTON_HOLD
 #define IMX233_BUTTON_LRADC_HOLD_DET BLH_ADC
 #endif
 
+/* VDDIO value */
+#if defined(CREATIVE_ZENXFISTYLE)
+#define IMX233_BUTTON_LRADC_VDDIO   3660
+#elif defined(CREATIVE_ZEN)
+#define IMX233_BUTTON_LRADC_VDDIO   3480
+#elif defined(CREATIVE_ZENXFI)
+#define IMX233_BUTTON_LRADC_VDDIO   3500
+#endif
+
+/* LRADC channel */
 #if defined(CREATIVE_ZENXFISTYLE)
 #define IMX233_BUTTON_LRADC_CHANNEL 2
 #else

firmware/target/arm/imx233/lradc-imx233.h

@@ -65,6 +65,9 @@
 /* frequency of the delay counter */
 #define LRADC_DELAY_FREQ    2000
 
+/* maximum value of a sample (without accumulation), defines the precision */
+#define LRADC_MAX_VALUE     4096
+
 typedef void (*lradc_irq_fn_t)(int chan);
 
 void imx233_lradc_init(void);