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/*
* (C) 2015 Siarhei Siamashka <siarhei.siamashka@gmail.com>
*
* SPDX-License-Identifier: GPL-2.0+
*/
/*
* Support for the SSD2828 bridge chip, which can take pixel data coming
* from a parallel LCD interface and translate it on the flight into MIPI DSI
* interface for driving a MIPI compatible TFT display.
*
* Implemented as a utility function. To be used from display drivers, which are
* responsible for driving parallel LCD hardware in front of the video pipeline.
*/
#ifndef _SSD2828_H
#define _SSD2828_H
struct ctfb_res_modes;
struct ssd2828_config {
/*********************************************************************/
/* SSD2828 configuration */
/*********************************************************************/
/*
* The pins, which are used for SPI communication. This is only used
* for configuring SSD2828, so the performance is irrelevant (only
* around a hundred of bytes is moved). Also these can be any arbitrary
* GPIO pins (not necessarily the pins having hardware SPI function).
* Moreover, the 'sdo' pin may be even not wired up in some devices.
*
* These configuration variables need to be set as pin numbers for
* the standard u-boot GPIO interface (gpio_get_value/gpio_set_value
* functions). Note that -1 value can be used for the pins, which are
* not really wired up.
*/
int csx_pin;
int sck_pin;
int sdi_pin;
int sdo_pin;
/* SSD2828 reset pin (shared with LCD panel reset) */
int reset_pin;
/*
* The SSD2828 has its own dedicated clock source 'tx_clk' (connected
* to TX_CLK_XIO/TX_CLK_XIN pins), which is necessary at least for
* clocking SPI after reset. The exact clock speed is not strictly,
* defined, but the datasheet says that it must be somewhere in the
* 8MHz - 30MHz range (see "TX_CLK Timing" section). It is used as
* a reference clock for PLL and must be set correctly.
*/
int ssd2828_tx_clk_khz;
/*
* This is not a property of the used LCD panel, but more like a
* property of the SSD2828 wiring. See the "SSD2828QN4 RGB data
* arrangement" table in the datasheet. The SSD2828 pins are arranged
* in such a way that 18bpp and 24bpp configurations are completely
* incompatible with each other.
*
* Depending on the color depth, this must be set to 16, 18 or 24.
*/
int ssd2828_color_depth;
/*********************************************************************/
/* LCD panel configuration */
/*********************************************************************/
/*
* The number of lanes in the MIPI DSI interface. May vary from 1 to 4.
*
* This information can be found in the LCD panel datasheet.
*/
int mipi_dsi_number_of_data_lanes;
/*
* Data transfer bit rate per lane. Please note that it is expected
* to be higher than the pixel clock rate of the used video mode when
* multiplied by the number of lanes. This is perfectly normal because
* MIPI DSI handles data transfers in periodic bursts, and uses the
* idle time between bursts for sending configuration information and
* commands. Or just for saving power.
*
* The necessary Mbps/lane information can be found in the LCD panel
* datasheet. Note that the transfer rate can't be always set precisely
* and it may be rounded *up* (introducing no more than 10Mbps error).
*/
int mipi_dsi_bitrate_per_data_lane_mbps;
/*
* Setting this to 1 enforces packing of 18bpp pixel data in 24bpp
* envelope when sending it over the MIPI DSI link.
*
* If unsure, set to 0.
*/
int mipi_dsi_loosely_packed_pixel_format;
/*
* According to the "Example for system sleep in and out" section in
* the SSD2828 datasheet, some LCD panel specific delays are necessary
* after MIPI DCS commands EXIT_SLEEP_MODE and SET_DISPLAY_ON.
*
* For example, Allwinner uses 100 milliseconds delay after
* EXIT_SLEEP_MODE and 200 milliseconds delay after SET_DISPLAY_ON.
*/
int mipi_dsi_delay_after_exit_sleep_mode_ms;
int mipi_dsi_delay_after_set_display_on_ms;
};
/*
* Initialize the SSD2828 chip. It needs the 'ssd2828_config' structure
* and also the video mode timings.
*
* The right place to insert this function call is after the parallel LCD
* interface is initialized and before turning on the backlight. This is
* advised in the "Example for system sleep in and out" section of the
* SSD2828 datasheet.
*/
int ssd2828_init(const struct ssd2828_config *cfg,
const struct ctfb_res_modes *mode);
#endif
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