drm/panel/raspberrypi-ts: Insert delay before polling for startup state

In switching to the hardware I2C controller there is an issue
where we seem to not get back the correct state from the Pi
touchscreen.
Insert a delay before polling to avoid this condition.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

diff --git a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
index 7ebb5ee..abb8a85 100644 (file)
--- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
+++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
@@ -299,6 +299,7 @@ static int rpi_touchscreen_enable(struct drm_panel *panel)
        int i;
 
        rpi_touchscreen_i2c_write(ts, REG_POWERON, 1);
+       usleep_range(20000, 25000);
        /* Wait for nPWRDWN to go low to indicate poweron is done. */
        for (i = 0; i < 100; i++) {
                if (rpi_touchscreen_i2c_read(ts, REG_PORTB) & 1)