drm/bridge: add support for sn65dsi86 bridge driver

Add support for TI's sn65dsi86 dsi2edp bridge chip.
The chip converts DSI transmitted signal to eDP signal,
which is fed to the connected eDP panel.

This chip can be controlled via either i2c interface or
dsi interface. Currently in driver all the control registers
are being accessed through i2c interface only.
Also as of now HPD support has not been added to bridge
chip driver.

Changes in v1:
 - Split the dt-bindings and the driver support into separate patches
   (Andrzej Hajda).
 - Use of gpiod APIs to parse and configure gpios instead of obsolete ones
   (Andrzej Hajda).
 - Use macros to define the register offsets (Andrzej Hajda).

Changes in v2:
 - Separate out edp panel specific HW resource handling from bridge
   driver and create a separate edp panel drivers to handle panel
   specific mode information and HW resources (Sean Paul).
 - Replace pr_* APIs to DRM_* APIs to log error or debug information
   (Sean Paul).
 - Remove some of the unnecessary structure/variable from driver (Sean
   Paul).
 - Rename the function and structure prefix "sn65dsi86" to "ti_sn_bridge"
   (Sean Paul / Rob Herring).
 - Remove most of the hard-coding and modified the bridge init sequence
   based on current mode (Sean Paul).
 - Remove the existing function to retrieve the EDID data and
   implemented this as an i2c_adapter and use drm_get_edid() (Sean Paul).
 - Remove the dummy irq handler implementation, will add back the
   proper irq handling later (Sean Paul).
 - Capture the required enable gpios in a single array based on dt entry
   instead of having individual descriptor for each gpio (Sean Paul).

Changes in v3:
 - Remove usage of irq_gpio and replace it as "interrupts" property (Rob
   Herring).
 - Remove the unnecessary header file inclusions (Sean Paul).
 - Rearrange the header files in alphabetical order (Sean Paul).
 - Use regmap interface to perform i2c transactions.
 - Update Copyright/License field and address other review comments
   (Jordan Crouse).

Changes in v4:
 - Update License/Copyright (Sean Paul).
 - Add Kconfig and Makefile changes (Sean Paul).
 - Drop i2c gpio handling from this bridge driver, since i2c sda/scl gpios
   will be handled by i2c master.
 - Update required supplies names.
 - Remove unnecessary goto statements (Sean Paul).
 - Add mutex lock to power_ctrl API to avoid race conditions (Sean
   Paul).
 - Add support to parse reference clk frequency from dt(optional).
 - Update the bridge chip enable/disable sequence.

Changes in v5:
 - Fixed Kbuild test service reported warnings.

Changes in v6:
 - Use PM runtime based ref-counting instead of local ref_count mechanism
   (Stephen Boyd).
 - Clean up some debug logs and indentations (Sean Paul).
 - Simplify dp rate calculation (Sean Paul).
 - Add support to configure refclk based on input REFCLK pin or DACP/N
   pin (Stephen Boyd).

Changes in v7:
 - Use static supply entries instead of dynamic allocation (Andrzej
   Hajda).
 - Defer bridge driver probe if panel is not probed (Andrzej Hajda).
 - Update of_graph APIs for correct node reference management. (Andrzej
   Hajda).
 - Remove local display_mode object (Andrzej Hajda).
 - Remove version id check function from driver.

Changes in v8:
 - Move dsi register/attach function to bridge driver probe (Andrzej
   Hajda).
 - Introduce a new helper function to write 16bit words into consecutive
   registers (Andrzej Hajda).
 - Remove unnecessary macros (Andrzej Hajda).

Changes in v9:
 - Remove dsi register/attach from bridge probe, since dsi dev register
   completion also waits for any panel or bridge to get added. This creates
   deadlock situation when bridge driver calls dsi dev register and
   attach before bridge add, in its probe function.
 - Fix issues faced during testing of bridge driver on actual HW.
 - Remove unnecessary initializations (Stephen Boyd).
 - Use local refclk lut size instead of global macro (Sean Paul).

Changes in v10:
 - Use refclk to determine if continuous dsi clock is needed or not.

Changes in v11:
 - Read DPPLL_SRC register to determine continuous clock instead of
   using refclk handle (Stephen Boyd).

Changes in v12:
 - Explain in comment as in why dsi dev registration is done in
   bridge_attach (Andrzej Hajda).
 - Move HPD disable to bridge_pre_enable (Andrzej Hajda).
 - Make panel/DDC exclusive until HPD support is added (Andrzej Hajda).

Changes in v13:
 - eDP panels report EDID via DP-AUX channel, so remove support for
   dedicated DDC line (Andrzej Hajda).

Changes in v14:
 - Remove unnecessary drm_panel checks (Andrzej Hajda).

Signed-off-by: Sandeep Panda <spanda@codeaurora.org>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1532069642-21392-1-git-send-email-spanda@codeaurora.org