drm: Add helper for DP++ adaptors

Add a helper which aids in the identification of DP dual mode
(aka. DP++) adaptors. There are several types of adaptors
specified: type 1 DVI, type 1 HDMI, type 2 DVI, type 2 HDMI

Type 1 adaptors have a max TMDS clock limit of 165MHz, type 2 adaptors
may go as high as 300MHz and they provide a register informing the
source device what the actual limit is. Supposedly also type 1 adaptors
may optionally implement this register. This TMDS clock limit is the
main reason why we need to identify these adaptors.

Type 1 adaptors provide access to their internal registers and the sink
DDC bus through I2C. Type 2 adaptors provide this access both via I2C
and I2C-over-AUX. A type 2 source device may choose to implement either
of these methods. If a source device implements the I2C-over-AUX
method, then the driver will obviously need specific support for such
adaptors since the port is driven like an HDMI port, but DDC
communication happes over the AUX channel.

This helper should be enough to identify the adaptor type (some
type 1 DVI adaptors may be a slight exception) and the maximum TMDS
clock limit. Another feature that may be available is control over
the TMDS output buffers on the adaptor, possibly allowing for some
power saving when the TMDS link is down.

Other user controllable features that may be available in the adaptors
are downstream i2c bus speed control when using i2c-over-aux, and
some control over the CEC pin. I chose not to provide any helper
functions for those since I have no use for them in i915 at this time.
The rest of the registers in the adaptor are mostly just information,
eg. IEEE OUI, hardware and firmware revision, etc.

v2: Pass adaptor type to helper functions to ease driver implementation
    Fix a bunch of typoes (Paulo)
    Add DRM_DP_DUAL_MODE_UNKNOWN for the case where we don't (yet) know
    the type (Paulo)
    Reject 0x00 and 0xff DP_DUAL_MODE_MAX_TMDS_CLOCK values (Paulo)
    Adjust drm_dp_dual_mode_detect() type2 vs. type1 detection to
    ease future LSPCON enabling
    Remove the unused DP_DUAL_MODE_LAST_RESERVED define
v3: Fix kernel doc function argument descriptions (Jani)
    s/NONE/UNKNOWN/ in drm_dp_dual_mode_detect() docs
    Add kernel doc for enum drm_dp_dual_mode_type
    Actually build the docs
    Fix more typoes
v4: Adjust code indentation of type2 adaptor detection (Shashank)
    Add debug messages for failurs cases (Shashank)
v5: EXPORT_SYMBOL(drm_dp_dual_mode_read) (Paulo)

Cc: stable@vger.kernel.org
Cc: Tore Anderson <tore@fud.no>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com> (v4)
Link: http://patchwork.freedesktop.org/patch/msgid/1462542412-25533-1-git-send-email-ville.syrjala@linux.intel.com

Documentation/DocBook/gpu.tmpl

@@ -1621,6 +1621,12 @@ void intel_crt_init(struct drm_device *dev)
 !Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
 !Iinclude/drm/drm_dp_helper.h
 !Edrivers/gpu/drm/drm_dp_helper.c
+    </sect2>
+    <sect2>
+      <title>Display Port Dual Mode Adaptor Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_dp_dual_mode_helper.c dp dual mode helpers
+!Iinclude/drm/drm_dp_dual_mode_helper.h
+!Edrivers/gpu/drm/drm_dp_dual_mode_helper.c
     </sect2>
     <sect2>
       <title>Display Port MST Helper Functions Reference</title>

drivers/gpu/drm/Makefile

@@ -23,7 +23,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o
 
 drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
 		drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
-		drm_kms_helper_common.o
+		drm_kms_helper_common.o drm_dp_dual_mode_helper.o
 
 drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o

include/drm/drm_dp_dual_mode_helper.h

+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef DRM_DP_DUAL_MODE_HELPER_H
+#define DRM_DP_DUAL_MODE_HELPER_H
+
+#include <linux/types.h>
+
+/*
+ * Optional for type 1 DVI adaptors
+ * Mandatory for type 1 HDMI and type 2 adaptors
+ */
+#define DP_DUAL_MODE_HDMI_ID 0x00 /* 00-0f */
+#define  DP_DUAL_MODE_HDMI_ID_LEN 16
+/*
+ * Optional for type 1 adaptors
+ * Mandatory for type 2 adaptors
+ */
+#define DP_DUAL_MODE_ADAPTOR_ID 0x10
+#define  DP_DUAL_MODE_REV_MASK 0x07
+#define  DP_DUAL_MODE_REV_TYPE2 0x00
+#define  DP_DUAL_MODE_TYPE_MASK 0xf0
+#define  DP_DUAL_MODE_TYPE_TYPE2 0xa0
+#define DP_DUAL_MODE_IEEE_OUI 0x11 /* 11-13*/
+#define  DP_DUAL_IEEE_OUI_LEN 3
+#define DP_DUAL_DEVICE_ID 0x14 /* 14-19 */
+#define  DP_DUAL_DEVICE_ID_LEN 6
+#define DP_DUAL_MODE_HARDWARE_REV 0x1a
+#define DP_DUAL_MODE_FIRMWARE_MAJOR_REV 0x1b
+#define DP_DUAL_MODE_FIRMWARE_MINOR_REV 0x1c
+#define DP_DUAL_MODE_MAX_TMDS_CLOCK 0x1d
+#define DP_DUAL_MODE_I2C_SPEED_CAP 0x1e
+#define DP_DUAL_MODE_TMDS_OEN 0x20
+#define  DP_DUAL_MODE_TMDS_DISABLE 0x01
+#define DP_DUAL_MODE_HDMI_PIN_CTRL 0x21
+#define  DP_DUAL_MODE_CEC_ENABLE 0x01
+#define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22
+
+struct i2c_adapter;
+
+ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
+			      u8 offset, void *buffer, size_t size);
+ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
+			       u8 offset, const void *buffer, size_t size);
+
+/**
+ * enum drm_dp_dual_mode_type - Type of the DP dual mode adaptor
+ * @DRM_DP_DUAL_MODE_NONE: No DP dual mode adaptor
+ * @DRM_DP_DUAL_MODE_UNKNOWN: Could be either none or type 1 DVI adaptor
+ * @DRM_DP_DUAL_MODE_TYPE1_DVI: Type 1 DVI adaptor
+ * @DRM_DP_DUAL_MODE_TYPE1_HDMI: Type 1 HDMI adaptor
+ * @DRM_DP_DUAL_MODE_TYPE2_DVI: Type 2 DVI adaptor
+ * @DRM_DP_DUAL_MODE_TYPE2_HDMI: Type 2 HDMI adaptor
+ */
+enum drm_dp_dual_mode_type {
+	DRM_DP_DUAL_MODE_NONE,
+	DRM_DP_DUAL_MODE_UNKNOWN,
+	DRM_DP_DUAL_MODE_TYPE1_DVI,
+	DRM_DP_DUAL_MODE_TYPE1_HDMI,
+	DRM_DP_DUAL_MODE_TYPE2_DVI,
+	DRM_DP_DUAL_MODE_TYPE2_HDMI,
+};
+
+enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter);
+int drm_dp_dual_mode_max_tmds_clock(enum drm_dp_dual_mode_type type,
+				    struct i2c_adapter *adapter);
+int drm_dp_dual_mode_get_tmds_output(enum drm_dp_dual_mode_type type,
+				     struct i2c_adapter *adapter, bool *enabled);
+int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
+				     struct i2c_adapter *adapter, bool enable);
+const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type);
+
+#endif