[Intel-gfx] [PATCH RESEND FOR CI 07/10] drm/i915/dsi: Document always using v3 SHUTDOWN / MIPI_SEQ_DISPLAY_OFF order

[Jani Nikula]

From: Hans de Goede <hdegoede at redhat.com>

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>
Reviewed-by: Bob Paauwe <bob.j.paauwe at intel.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/i915/intel_dsi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index b132841587cc..5a50645c3a37 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -872,6 +872,11 @@ static void intel_dsi_pre_disable(struct intel_encoder *encoder,
 			I915_WRITE(MIPI_DEVICE_READY(port), 0);
 	}
 
+	/*
+	 * According to the spec we should send SHUTDOWN before
+	 * MIPI_SEQ_DISPLAY_OFF only for v3+ VBTs, but field testing
+	 * has shown that the v3 sequence works 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)
-- 
2.1.4