[PATCH v2] drm/i915/dmc: fix assert_dmc_loaded WARN during async firmware load

[James Xiong <james.xiong@intel.com>]

During driver probe, DMC firmware is loaded asynchronously via a
workqueue. There is a race between parse_dmc_fw() setting the payload
pointer (making has_dmc_id_fw() return true) and intel_dmc_load_program()
writing the firmware to hardware registers. If the probe thread calls
intel_dmc_enable_pipe() -> assert_dmc_loaded() in this window via
intel_modeset_setup_hw_state(), it sees parsed payload but stale HW
registers, triggering a ~20% intermittent WARNING on ADL-N warm boot.

v2: Fix by calling intel_dmc_wait_fw_load() in
    intel_modeset_setup_hw_state() before iterating the CRTCs (Gustavo
    Sousa).

Signed-off-by: James Xiong <james.xiong@intel.com>
---
 drivers/gpu/drm/i915/display/intel_modeset_setup.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_modeset_setup.c b/drivers/gpu/drm/i915/display/intel_modeset_setup.c
index e88082c8caac..277e56848470 100644
--- a/drivers/gpu/drm/i915/display/intel_modeset_setup.c
+++ b/drivers/gpu/drm/i915/display/intel_modeset_setup.c
@@ -961,6 +961,8 @@ void intel_modeset_setup_hw_state(struct intel_display *display,
 	 * intel_sanitize_plane_mapping() may need to do vblank
 	 * waits, so we need vblank interrupts restored beforehand.
 	 */
+	intel_dmc_wait_fw_load(display);
+
 	for_each_intel_crtc(display->drm, crtc) {
 		struct intel_crtc_state *crtc_state =
 			to_intel_crtc_state(crtc->base.state);
-- 
2.34.1