/* * Copyright (c) 2015 NVIDIA Corporation. All rights reserved. * * 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, sub license, * 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 (including the * next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS 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. */ #include <linux/i2c.h> #include <linux/slab.h> #include <linux/delay.h> #include <drm/display/drm_scdc_helper.h> #include <drm/drm_connector.h> #include <drm/drm_device.h> #include <drm/drm_print.h> /** * DOC: scdc helpers * * Status and Control Data Channel (SCDC) is a mechanism introduced by the * HDMI 2.0 specification. It is a point-to-point protocol that allows the * HDMI source and HDMI sink to exchange data. The same I2C interface that * is used to access EDID serves as the transport mechanism for SCDC. * * Note: The SCDC status is going to be lost when the display is * disconnected. This can happen physically when the user disconnects * the cable, but also when a display is switched on (such as waking up * a TV). * * This is further complicated by the fact that, upon a disconnection / * reconnection, KMS won't change the mode on its own. This means that * one can't just rely on setting the SCDC status on enable, but also * has to track the connector status changes using interrupts and * restore the SCDC status. The typical solution for this is to trigger an * empty modeset in drm_connector_helper_funcs.detect_ctx(), like what vc4 does * in vc4_hdmi_reset_link(). */ #define SCDC_I2C_SLAVE_ADDRESS … /** * drm_scdc_read - read a block of data from SCDC * @adapter: I2C controller * @offset: start offset of block to read * @buffer: return location for the block to read * @size: size of the block to read * * Reads a block of data from SCDC, starting at a given offset. * * Returns: * 0 on success, negative error code on failure. */ ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, size_t size) { … } EXPORT_SYMBOL(…); /** * drm_scdc_write - write a block of data to SCDC * @adapter: I2C controller * @offset: start offset of block to write * @buffer: block of data to write * @size: size of the block to write * * Writes a block of data to SCDC, starting at a given offset. * * Returns: * 0 on success, negative error code on failure. */ ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset, const void *buffer, size_t size) { … } EXPORT_SYMBOL(…); /** * drm_scdc_get_scrambling_status - what is status of scrambling? * @connector: connector * * Reads the scrambler status over SCDC, and checks the * scrambling status. * * Returns: * True if the scrambling is enabled, false otherwise. */ bool drm_scdc_get_scrambling_status(struct drm_connector *connector) { … } EXPORT_SYMBOL(…); /** * drm_scdc_set_scrambling - enable scrambling * @connector: connector * @enable: bool to indicate if scrambling is to be enabled/disabled * * Writes the TMDS config register over SCDC channel, and: * enables scrambling when enable = 1 * disables scrambling when enable = 0 * * Returns: * True if scrambling is set/reset successfully, false otherwise. */ bool drm_scdc_set_scrambling(struct drm_connector *connector, bool enable) { … } EXPORT_SYMBOL(…); /** * drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio * @connector: connector * @set: ret or reset the high clock ratio * * * TMDS clock ratio calculations go like this: * TMDS character = 10 bit TMDS encoded value * * TMDS character rate = The rate at which TMDS characters are * transmitted (Mcsc) * * TMDS bit rate = 10x TMDS character rate * * As per the spec: * TMDS clock rate for pixel clock < 340 MHz = 1x the character * rate = 1/10 pixel clock rate * * TMDS clock rate for pixel clock > 340 MHz = 0.25x the character * rate = 1/40 pixel clock rate * * Writes to the TMDS config register over SCDC channel, and: * sets TMDS clock ratio to 1/40 when set = 1 * * sets TMDS clock ratio to 1/10 when set = 0 * * Returns: * True if write is successful, false otherwise. */ bool drm_scdc_set_high_tmds_clock_ratio(struct drm_connector *connector, bool set) { … } EXPORT_SYMBOL(…);
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