Input: mt6779-keypad - implement row/column selection

The MediaTek keypad has a total of 6 input rows and 6 input columns.
By default, rows/columns 0-2 are enabled.

This is controlled by the KP_SEL register:
- bits[9:4]   control row selection
- bits[15:10] control column selection

Each bit enables the corresponding row/column number (e.g KP_SEL[4]
enables ROW0)

Depending on how the keypad is wired, this may result in wrong readings
of the keypad state.

Program the KP_SEL register to limit the key detection to n_rows,
n_cols we retrieve from the device tree.

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20220707075236.126631-3-mkorpershoek@baylibre.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/keyboard/mt6779-keypad.c

@@ -17,6 +17,11 @@
 #define MTK_KPD_DEBOUNCE	0x0018
 #define MTK_KPD_DEBOUNCE_MASK	GENMASK(13, 0)
 #define MTK_KPD_DEBOUNCE_MAX_MS	256
+#define MTK_KPD_SEL		0x0020
+#define MTK_KPD_SEL_COL	GENMASK(15, 10)
+#define MTK_KPD_SEL_ROW	GENMASK(9, 4)
+#define MTK_KPD_SEL_COLMASK(c)	GENMASK((c) + 9, 10)
+#define MTK_KPD_SEL_ROWMASK(r)	GENMASK((r) + 3, 4)
 #define MTK_KPD_NUM_MEMS	5
 #define MTK_KPD_NUM_BITS	136	/* 4*32+8 MEM5 only use 8 BITS */
 
@@ -161,6 +166,11 @@ static int mt6779_keypad_pdrv_probe(struct platform_device *pdev)
 	regmap_write(keypad->regmap, MTK_KPD_DEBOUNCE,
 		     (debounce * (1 << 5)) & MTK_KPD_DEBOUNCE_MASK);
 
+	regmap_update_bits(keypad->regmap, MTK_KPD_SEL, MTK_KPD_SEL_ROW,
+			   MTK_KPD_SEL_ROWMASK(keypad->n_rows));
+	regmap_update_bits(keypad->regmap, MTK_KPD_SEL, MTK_KPD_SEL_COL,
+			   MTK_KPD_SEL_COLMASK(keypad->n_cols));
+
 	keypad->clk = devm_clk_get(&pdev->dev, "kpd");
 	if (IS_ERR(keypad->clk))
 		return PTR_ERR(keypad->clk);