drm/radeon/kms: ATPX switcheroo fixes

When we switch the display mux, also switch
the i2c mux.  Also use the start and finish
methods to let the sbios know that the switch
is happening.

Should fix:
https://bugs.freedesktop.org/show_bug.cgi?id=35398

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_atpx_handler.c

@@ -15,6 +15,9 @@
 #define ATPX_VERSION 0
 #define ATPX_GPU_PWR 2
 #define ATPX_MUX_SELECT 3
+#define ATPX_I2C_MUX_SELECT 4
+#define ATPX_SWITCH_START 5
+#define ATPX_SWITCH_END 6
 
 #define ATPX_INTEGRATED 0
 #define ATPX_DISCRETE 1
@@ -149,13 +152,35 @@ static int radeon_atpx_switch_mux(acpi_handle handle, int mux_id)
 	return radeon_atpx_execute(handle, ATPX_MUX_SELECT, mux_id);
 }
 
+static int radeon_atpx_switch_i2c_mux(acpi_handle handle, int mux_id)
+{
+	return radeon_atpx_execute(handle, ATPX_I2C_MUX_SELECT, mux_id);
+}
+
+static int radeon_atpx_switch_start(acpi_handle handle, int gpu_id)
+{
+	return radeon_atpx_execute(handle, ATPX_SWITCH_START, gpu_id);
+}
+
+static int radeon_atpx_switch_end(acpi_handle handle, int gpu_id)
+{
+	return radeon_atpx_execute(handle, ATPX_SWITCH_END, gpu_id);
+}
 
 static int radeon_atpx_switchto(enum vga_switcheroo_client_id id)
 {
+	int gpu_id;
+
 	if (id == VGA_SWITCHEROO_IGD)
-		radeon_atpx_switch_mux(radeon_atpx_priv.atpx_handle, 0);
+		gpu_id = ATPX_INTEGRATED;
 	else
-		radeon_atpx_switch_mux(radeon_atpx_priv.atpx_handle, 1);
+		gpu_id = ATPX_DISCRETE;
+
+	radeon_atpx_switch_start(radeon_atpx_priv.atpx_handle, gpu_id);
+	radeon_atpx_switch_mux(radeon_atpx_priv.atpx_handle, gpu_id);
+	radeon_atpx_switch_i2c_mux(radeon_atpx_priv.atpx_handle, gpu_id);
+	radeon_atpx_switch_end(radeon_atpx_priv.atpx_handle, gpu_id);
+
 	return 0;
 }