Input: matrix_keypad - add settle time after enabling all columns

Matrix keypads with high capacity need a longer settle time after
enabling all columns before re-enabling interrupts. The delay gives
the system time to settle and avoids spurious interrupts.

Add a new optional device property to configure the delay after
enabling all columns. The default is no delay.

Signed-off-by: Markus Burri <markus.burri@mt.com>
Reviewed-by: Manuel Traut <manuel.traut@mt.com>
Link: https://lore.kernel.org/r/20250110054906.354296-7-markus.burri@mt.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Author: Markus Burri

drivers/input/keyboard/matrix_keypad.c

@@ -26,6 +26,7 @@ struct matrix_keypad {
 	unsigned int row_shift;
 
 	unsigned int col_scan_delay_us;
+	unsigned int all_cols_on_delay_us;
 	/* key debounce interval in milli-second */
 	unsigned int debounce_ms;
 	bool drive_inactive_cols;
@@ -77,6 +78,9 @@ static void activate_all_cols(struct matrix_keypad *keypad, bool on)
 
 	for (col = 0; col < keypad->num_col_gpios; col++)
 		__activate_col(keypad, col, on);
+
+	if (on && keypad->all_cols_on_delay_us)
+		fsleep(keypad->all_cols_on_delay_us);
 }
 
 static bool row_asserted(struct matrix_keypad *keypad, int row)
@@ -392,6 +396,8 @@ static int matrix_keypad_probe(struct platform_device *pdev)
 				 &keypad->debounce_ms);
 	device_property_read_u32(&pdev->dev, "col-scan-delay-us",
 				 &keypad->col_scan_delay_us);
+	device_property_read_u32(&pdev->dev, "all-cols-on-delay-us",
+				 &keypad->all_cols_on_delay_us);
 
 	err = matrix_keypad_init_gpio(pdev, keypad);
 	if (err)