[PATCH 1/1] UBUNTU: SAUCE: drm/i915: Disable writing of TMDS_OE on Lenovo ThinkPad X1 series

[Aaron Ma]

BugLink: https://bugs.launchpad.net/bugs/1738523

There is a hw design on Lenovo ThinkPad X1 yoga/carbon:
Intel GEN9 display -> AlpineRidge -> PS8407 -> HDMI output

When switch mode on this HDMI output, it failed to writing on
I2C device 0x40/0x50. Then sometimes the HDMI output is disabled.

>From Parade's support, tmds_oe is enabled by default, and keep it
enabled to fix this issue.

Add a workaround to bypass this TMDS_OE writing on identified
laptop models.

Signed-off-by: Aaron Ma <aaron.ma at canonical.com>
---
 drivers/gpu/drm/i915/i915_drv.h   |  3 +++
 drivers/gpu/drm/i915/intel_bios.c | 18 ++++++++++++++++++
 drivers/gpu/drm/i915/intel_hdmi.c |  5 +++++
 3 files changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0d3848b4f000..46bc91ad6719 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2576,6 +2576,9 @@ struct drm_i915_private {
 
 	bool ipc_enabled;
 
+	/* Hack to bypass TMDS_OE write on DP->HDMI dongle */
+	bool bypass_tmds_oe;
+
 	/* Used to save the pipe-to-encoder mapping for audio */
 	struct intel_encoder *av_enc_map[I915_MAX_PIPES];
 
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index f814359c86c9..0be1d38feaec 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -29,6 +29,7 @@
 #include <drm/drmP.h>
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
+#include <linux/dmi.h>
 
 #define _INTEL_BIOS_PRIVATE
 #include "intel_vbt_defs.h"
@@ -1481,6 +1482,22 @@ static const struct vbt_header *find_vbt(void __iomem *bios, size_t size)
 	return NULL;
 }
 
+#define DRM_DMI_PRODUCT_VERSION 0x6
+
+static void parse_product_info(struct drm_i915_private *dev_priv)
+{
+	const char *product_ver = dmi_get_system_info(DRM_DMI_PRODUCT_VERSION);
+	if (!product_ver)
+		return;
+
+	if (!strncmp(product_ver, "ThinkPad X1", 11)) {
+		DRM_DEBUG_KMS("dmi: %s, Bypassing TMDS_OE write\n", product_ver);
+		dev_priv->bypass_tmds_oe = true;
+	}
+
+	return;
+}
+
 /**
  * intel_bios_init - find VBT and initialize settings from the BIOS
  * @dev_priv: i915 device instance
@@ -1537,6 +1554,7 @@ void intel_bios_init(struct drm_i915_private *dev_priv)
 	parse_mipi_config(dev_priv, bdb);
 	parse_mipi_sequence(dev_priv, bdb);
 	parse_ddi_ports(dev_priv, bdb);
+	parse_product_info(dev_priv);
 
 out:
 	if (!vbt) {
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index ec0779a52d53..01837b9f7d76 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -851,6 +851,11 @@ void intel_dp_dual_mode_set_tmds_output(struct intel_hdmi *hdmi, bool enable)
 	if (hdmi->dp_dual_mode.type < DRM_DP_DUAL_MODE_TYPE2_DVI)
 		return;
 
+	if (dev_priv->bypass_tmds_oe) {
+		DRM_DEBUG_KMS("Bypassing TMDS_OE setting\n");
+		return;
+	}
+
 	DRM_DEBUG_KMS("%s DP dual mode adaptor TMDS output\n",
 		      enable ? "Enabling" : "Disabling");
 
-- 
2.13.6