From b3daa5ef52c26acd7432c787989bd92d48070c76 Mon Sep 17 00:00:00 2001 From: Ville Syrjälä Date: Fri, 6 May 2016 16:46:52 +0300 Subject: drm: Add helper for DP++ adaptors MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Paulo Zanoni Cc: Shashank Sharma Cc: Daniel Vetter Cc: Shashank Sharma Signed-off-by: Ville Syrjälä Reviewed-by: Shashank Sharma (v4) Link: http://patchwork.freedesktop.org/patch/msgid/1462542412-25533-1-git-send-email-ville.syrjala@linux.intel.com (cherry picked from commit ede53344dbfd1dd43bfd73eb6af743d37c56a7c3) Signed-off-by: Jani Nikula --- Documentation/DocBook/gpu.tmpl | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'Documentation') diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl index 1464fb2f3c46..c248124357df 100644 --- a/Documentation/DocBook/gpu.tmpl +++ b/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 + + + Display Port Dual Mode Adaptor Helper Functions Reference +!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 Display Port MST Helper Functions Reference -- cgit v1.2.3