From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
The Parade LSPCON on KBL NUCs forgets to turn off scrambling/bit clock
rate when switching from a mode that needs them to a mode that does
not. This manifests as a "no signal" on my TV when I try to go from
4k to 1080p for example. Resetting the SCDC register bits with
i2cset is sufficient to restore the picture to the screen.
Here's the OUI/fw revision for the LSPCON chip in question:
DP branch: OUI 00-1c-f8 dev-ID 175IB0 HW-rev 1.0 SW-rev 7.32 quirks 0x0000
Asking users to poke at SCDC with i2cset is a bit much, so
let's work around this in the driver. We don't need to go all
out here and compute whether scrambling is needed or not as
LSPCON will do that itself. If scrambling is actually
required LSPCON does not forget to enable it.
Cc: Shashank Sharma <shashank.sharma@xxxxxxxxx>
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_ddi.c | 52 ++++++++++++++++++++++++++++---
drivers/gpu/drm/i915/intel_drv.h | 1 +
drivers/gpu/drm/i915/intel_hdmi.c | 5 ++-
3 files changed, 51 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 47960c92cbbf..ef502fc9add1 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2984,6 +2984,23 @@ static void intel_ddi_pre_enable(struct intel_encoder *encoder,
intel_ddi_pre_enable_dp(encoder, crtc_state, conn_state);
}
+static void intel_ddi_pre_enable_lspcon(struct intel_encoder *encoder,
+ const struct intel_crtc_state *crtc_state,
+ const struct drm_connector_state *conn_state)
+{
+ struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
+
+ intel_ddi_pre_enable(encoder, crtc_state, conn_state);
+
+ /*
+ * Parade LSPCON forgets to turn off scrambling/bit clock rate
+ * when switching from a mode that needs them to a mode that
+ * does not.
+ */
+ intel_hdmi_handle_sink_scrambling(encoder, conn_state->connector,
+ &intel_dp->aux.ddc, false, false);
+}
+
static void intel_disable_ddi_buf(struct intel_encoder *encoder)
{
struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
@@ -3086,6 +3103,23 @@ static void intel_ddi_post_disable(struct intel_encoder *encoder,
old_crtc_state, old_conn_state);
}
+static void intel_ddi_post_disable_lspcon(struct intel_encoder *encoder,
+ const struct intel_crtc_state *old_crtc_state,
+ const struct drm_connector_state *old_conn_state)
+{
+ struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
+
+ /*
+ * Parade LSPCON forgets to turn off scrambling/bit clock rate
+ * when switching from a mode that needs them to a mode that
+ * does not.
+ */
+ intel_hdmi_handle_sink_scrambling(encoder, old_conn_state->connector,
+ &intel_dp->aux.ddc, false, false);
+
+ intel_ddi_post_disable(encoder, old_crtc_state, old_conn_state);
+}
