drm/panel: Enable DSI transactions on the RPi panel.

It turns out that I had just mistaken what type of write the register
writes were supposed to be, using DCS instead of generic long writes.

Switching to transactions instead of using the atmel as a bridge also
seems to resolve the sparkling pixels problem I've had.

Signed-off-by: Eric Anholt <eric@anholt.net>
Fixes: 2f733d6194bd ("drm/panel: Add support for the Raspberry Pi 7" Touchscreen.")
Link: https://patchwork.freedesktop.org/patch/msgid/20171031193258.17373-2-eric@anholt.net
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
Acked-by: Thierry Reding <treding@nvidia.com>

diff --git a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
index d964d45..2c9c972 100644 (file)
--- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
+++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
@@ -238,12 +238,6 @@ static void rpi_touchscreen_i2c_write(struct rpi_touchscreen *ts,
 
 static int rpi_touchscreen_write(struct rpi_touchscreen *ts, u16 reg, u32 val)
 {
-#if 0
-       /* The firmware uses LP DSI transactions like this to bring up
-        * the hardware, which should be faster than using I2C to then
-        * pass to the Toshiba.  However, I was unable to get it to
-        * work.
-        */
        u8 msg[] = {
                reg,
                reg >> 8,
@@ -253,13 +247,7 @@ static int rpi_touchscreen_write(struct rpi_touchscreen *ts, u16 reg, u32 val)
                val >> 24,
        };
 
-       mipi_dsi_dcs_write_buffer(ts->dsi, msg, sizeof(msg));
-#else
-       rpi_touchscreen_i2c_write(ts, REG_WR_ADDRH, reg >> 8);
-       rpi_touchscreen_i2c_write(ts, REG_WR_ADDRL, reg);
-       rpi_touchscreen_i2c_write(ts, REG_WRITEH, val >> 8);
-       rpi_touchscreen_i2c_write(ts, REG_WRITEL, val);
-#endif
+       mipi_dsi_generic_write(ts->dsi, msg, sizeof(msg));
 
        return 0;
 }