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Diffstat (limited to 'drivers/video/ssd2828.h')
| -rw-r--r-- | drivers/video/ssd2828.h | 128 |
1 files changed, 128 insertions, 0 deletions
diff --git a/drivers/video/ssd2828.h b/drivers/video/ssd2828.h new file mode 100644 index 00000000000..1af6fa40232 --- /dev/null +++ b/drivers/video/ssd2828.h @@ -0,0 +1,128 @@ +/* + * (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 can be also + * used as a reference clock for PLL. If the exact clock frequency + * is known, then it can be specified here. If it is unknown, or the + * information is not trustworthy, then it can be set to 0. + * + * If unsure, set to 0. + */ + 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. And also SS2828 may use 'pclk' as the clock source + * for PLL, which means that the input signal must be already there. + */ +int ssd2828_init(const struct ssd2828_config *cfg, + const struct ctfb_res_modes *mode); + +#endif |