drm/i915: Add function to output Aksv over GMBUS

Once the Aksv is available in the PCH, we need to get it on the wire to
the receiver via DDC. The hardware doesn't allow us to read the value
directly, so we need to tell GMBUS to source the Aksv internally and
send it to the right offset on the receiver.

The way we do this is to initiate an indexed write where the index is
the Aksv register offset. We write dummy values to GMBUS3 as if we were
sending the key, and the hardware slips in the "real" values when it
goes out.

Changes in v2:
- None
Changes in v3:
- Uses new index write feature (Ville)
Changes in v4:
- None
Changes in v5:
- checkpatch whitespace fix
Changes in v6:
- None

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180108195545.218615-8-seanpaul@chromium.org

1 files changed, 44 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index d9e6993fa718..6f7ef4e225ee 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -30,6 +30,7 @@
 #include <linux/i2c-algo-bit.h>
 #include <linux/export.h>
 #include <drm/drmP.h>
+#include <drm/drm_hdcp.h>
 #include "intel_drv.h"
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
@@ -507,7 +508,8 @@ gmbus_index_xfer(struct drm_i915_private *dev_priv, struct i2c_msg *msgs)
 }
 
 static int
-do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
+do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num,
+	      u32 gmbus0_source)
 {
 	struct intel_gmbus *bus = container_of(adapter,
 					       struct intel_gmbus,
@@ -524,7 +526,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 		pch_gmbus_clock_gating(dev_priv, false);
 
 retry:
-	I915_WRITE_FW(GMBUS0, bus->reg0);
+	I915_WRITE_FW(GMBUS0, gmbus0_source | bus->reg0);
 
 	for (; i < num; i += inc) {
 		inc = 1;
@@ -649,7 +651,7 @@ gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 		if (ret < 0)
 			bus->force_bit &= ~GMBUS_FORCE_BIT_RETRY;
 	} else {
-		ret = do_gmbus_xfer(adapter, msgs, num);
+		ret = do_gmbus_xfer(adapter, msgs, num, 0);
 		if (ret == -EAGAIN)
 			bus->force_bit |= GMBUS_FORCE_BIT_RETRY;
 	}
@@ -659,6 +661,45 @@ gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
 	return ret;
 }
 
+int intel_gmbus_output_aksv(struct i2c_adapter *adapter)
+{
+	struct intel_gmbus *bus = container_of(adapter, struct intel_gmbus,
+					       adapter);
+	struct drm_i915_private *dev_priv = bus->dev_priv;
+	int ret;
+	u8 cmd = DRM_HDCP_DDC_AKSV;
+	u8 buf[DRM_HDCP_KSV_LEN] = { 0 };
+	struct i2c_msg msgs[] = {
+		{
+			.addr = DRM_HDCP_DDC_ADDR,
+			.flags = 0,
+			.len = sizeof(cmd),
+			.buf = &cmd,
+		},
+		{
+			.addr = DRM_HDCP_DDC_ADDR,
+			.flags = 0,
+			.len = sizeof(buf),
+			.buf = buf,
+		}
+	};
+
+	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
+	mutex_lock(&dev_priv->gmbus_mutex);
+
+	/*
+	 * In order to output Aksv to the receiver, use an indexed write to
+	 * pass the i2c command, and tell GMBUS to use the HW-provided value
+	 * instead of sourcing GMBUS3 for the data.
+	 */
+	ret = do_gmbus_xfer(adapter, msgs, ARRAY_SIZE(msgs), GMBUS_AKSV_SELECT);
+
+	mutex_unlock(&dev_priv->gmbus_mutex);
+	intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);
+
+	return ret;
+}
+
 static u32 gmbus_func(struct i2c_adapter *adapter)
 {
 	return i2c_bit_algo.functionality(adapter) &