[PATCH 15/18] drm/i915/dsi: Document always using v3 SHUTDOWN / MIPI_SEQ_DISPLAY_OFF order

[Hans de Goede]

According to the spec for v2 VBTs we should call MIPI_SEQ_DISPLAY_OFF
before sending SHUTDOWN, where as for v3 VBTs we should send SHUTDOWN
first.

Since the v2 order has known issues, we use the v3 order everywhere,
add a comment documenting this.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 drivers/gpu/drm/i915/intel_dsi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index 9b0c9152..7761806 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -708,6 +708,11 @@ static void intel_dsi_pre_disable(struct intel_encoder *encoder,
 	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_BACKLIGHT_OFF);
 	intel_panel_disable_backlight(intel_dsi->attached_connector);
 
+	/*
+	 * XXX: According to the spec we should send SHUTDOWN before
+	 * MIPI_SEQ_DISPLAY_OFF only for v3+ VBTs, but testing in the field
+	 * has shown that we should do this for v2 VBTs too?
+	 */
 	if (is_vid_mode(intel_dsi)) {
 		/* Send Shutdown command to the panel in LP mode */
 		for_each_dsi_port(port, intel_dsi->ports)
@@ -739,6 +744,8 @@ static void intel_dsi_post_disable(struct intel_encoder *encoder,
 	/*
 	 * if disable packets are sent before sending shutdown packet then in
 	 * some next enable sequence send turn on packet error is observed
+	 * XXX spec specifies SHUTDOWN before MIPI_SEQ_DISPLAY_OFF for
+	 * v3 VBTs, but not for v2 VBTs?
 	 */
 	intel_dsi_exec_vbt_sequence(intel_dsi, MIPI_SEQ_DISPLAY_OFF);
 
-- 
2.9.3