drm/radeon: program auxch directly (v2)

The atombios tables have an unfortunate restriction on only
being able to write 12 bytes, MST really wants 16-bytes here,
and since the hw can do it, we should just write directly to it.

This uses a module option to allow for it now, and maybe
we should provide the old code as a fallback for a while.

v2: (agd5f)
- move registers to a proper register header
- only enable on DCE5+
- enable by default on DCE5+
- Switch pad to aux mode before using it
- reformat instance handling to better match the
  rest of the driver

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
index 8d74de8..a014c7b 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -158,7 +158,7 @@
 #define HEADER_SIZE (BARE_ADDRESS_SIZE + 1)
 
 static ssize_t
-radeon_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
+radeon_dp_aux_transfer_atom(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
 {
 	struct radeon_i2c_chan *chan =
 		container_of(aux, struct radeon_i2c_chan, aux);
@@ -226,11 +226,20 @@
 
 void radeon_dp_aux_init(struct radeon_connector *radeon_connector)
 {
+	struct drm_device *dev = radeon_connector->base.dev;
+	struct radeon_device *rdev = dev->dev_private;
 	int ret;
 
 	radeon_connector->ddc_bus->rec.hpd = radeon_connector->hpd.hpd;
 	radeon_connector->ddc_bus->aux.dev = radeon_connector->base.kdev;
-	radeon_connector->ddc_bus->aux.transfer = radeon_dp_aux_transfer;
+	if (ASIC_IS_DCE5(rdev)) {
+		if (radeon_auxch)
+			radeon_connector->ddc_bus->aux.transfer = radeon_dp_aux_transfer_native;
+		else
+			radeon_connector->ddc_bus->aux.transfer = radeon_dp_aux_transfer_atom;
+	} else {
+		radeon_connector->ddc_bus->aux.transfer = radeon_dp_aux_transfer_atom;
+	}
 
 	ret = drm_dp_aux_register(&radeon_connector->ddc_bus->aux);
 	if (!ret)