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dddccd6913
Instead of using the internal 'tx_clk' clock source, it is also
possible to use the pixel clock signal from the parallel LCD
interface ('pclk') as the reference clock for PLL.
The 'tx_clk' clock speed may be different on different boards/devices
(the allowed range is 8MHz - 30MHz). Which is not very convenient,
especially considering the need to know the exact 'tx_clk' clock
speed. This clock speed may be difficult to identify without having
device schematics and/or accurate documentation/sources every time.
Using 'pclk' is free from all these problems.
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Anatolij Gustschin <agust@denx.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
129 lines
4.7 KiB
C
129 lines
4.7 KiB
C
/*
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* (C) 2015 Siarhei Siamashka <siarhei.siamashka@gmail.com>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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/*
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* Support for the SSD2828 bridge chip, which can take pixel data coming
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* from a parallel LCD interface and translate it on the flight into MIPI DSI
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* interface for driving a MIPI compatible TFT display.
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*
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* Implemented as a utility function. To be used from display drivers, which are
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* responsible for driving parallel LCD hardware in front of the video pipeline.
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*/
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#ifndef _SSD2828_H
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#define _SSD2828_H
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struct ctfb_res_modes;
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struct ssd2828_config {
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/*********************************************************************/
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/* SSD2828 configuration */
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/*********************************************************************/
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/*
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* The pins, which are used for SPI communication. This is only used
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* for configuring SSD2828, so the performance is irrelevant (only
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* around a hundred of bytes is moved). Also these can be any arbitrary
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* GPIO pins (not necessarily the pins having hardware SPI function).
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* Moreover, the 'sdo' pin may be even not wired up in some devices.
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*
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* These configuration variables need to be set as pin numbers for
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* the standard u-boot GPIO interface (gpio_get_value/gpio_set_value
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* functions). Note that -1 value can be used for the pins, which are
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* not really wired up.
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*/
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int csx_pin;
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int sck_pin;
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int sdi_pin;
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int sdo_pin;
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/* SSD2828 reset pin (shared with LCD panel reset) */
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int reset_pin;
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/*
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* The SSD2828 has its own dedicated clock source 'tx_clk' (connected
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* to TX_CLK_XIO/TX_CLK_XIN pins), which is necessary at least for
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* clocking SPI after reset. The exact clock speed is not strictly,
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* defined, but the datasheet says that it must be somewhere in the
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* 8MHz - 30MHz range (see "TX_CLK Timing" section). It can be also
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* used as a reference clock for PLL. If the exact clock frequency
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* is known, then it can be specified here. If it is unknown, or the
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* information is not trustworthy, then it can be set to 0.
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*
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* If unsure, set to 0.
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*/
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int ssd2828_tx_clk_khz;
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/*
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* This is not a property of the used LCD panel, but more like a
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* property of the SSD2828 wiring. See the "SSD2828QN4 RGB data
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* arrangement" table in the datasheet. The SSD2828 pins are arranged
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* in such a way that 18bpp and 24bpp configurations are completely
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* incompatible with each other.
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*
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* Depending on the color depth, this must be set to 16, 18 or 24.
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*/
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int ssd2828_color_depth;
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/*********************************************************************/
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/* LCD panel configuration */
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/*********************************************************************/
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/*
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* The number of lanes in the MIPI DSI interface. May vary from 1 to 4.
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*
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* This information can be found in the LCD panel datasheet.
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*/
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int mipi_dsi_number_of_data_lanes;
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/*
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* Data transfer bit rate per lane. Please note that it is expected
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* to be higher than the pixel clock rate of the used video mode when
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* multiplied by the number of lanes. This is perfectly normal because
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* MIPI DSI handles data transfers in periodic bursts, and uses the
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* idle time between bursts for sending configuration information and
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* commands. Or just for saving power.
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*
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* The necessary Mbps/lane information can be found in the LCD panel
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* datasheet. Note that the transfer rate can't be always set precisely
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* and it may be rounded *up* (introducing no more than 10Mbps error).
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*/
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int mipi_dsi_bitrate_per_data_lane_mbps;
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/*
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* Setting this to 1 enforces packing of 18bpp pixel data in 24bpp
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* envelope when sending it over the MIPI DSI link.
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*
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* If unsure, set to 0.
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*/
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int mipi_dsi_loosely_packed_pixel_format;
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/*
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* According to the "Example for system sleep in and out" section in
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* the SSD2828 datasheet, some LCD panel specific delays are necessary
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* after MIPI DCS commands EXIT_SLEEP_MODE and SET_DISPLAY_ON.
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*
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* For example, Allwinner uses 100 milliseconds delay after
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* EXIT_SLEEP_MODE and 200 milliseconds delay after SET_DISPLAY_ON.
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*/
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int mipi_dsi_delay_after_exit_sleep_mode_ms;
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int mipi_dsi_delay_after_set_display_on_ms;
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};
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/*
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* Initialize the SSD2828 chip. It needs the 'ssd2828_config' structure
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* and also the video mode timings.
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*
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* The right place to insert this function call is after the parallel LCD
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* interface is initialized and before turning on the backlight. This is
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* advised in the "Example for system sleep in and out" section of the
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* SSD2828 datasheet. And also SS2828 may use 'pclk' as the clock source
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* for PLL, which means that the input signal must be already there.
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*/
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int ssd2828_init(const struct ssd2828_config *cfg,
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const struct ctfb_res_modes *mode);
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#endif
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