--- /dev/null
+/*
+ * (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.
+ */
+
+#include <common.h>
+#include <mipi_display.h>
+#include <asm/arch/gpio.h>
+#include <asm/gpio.h>
+
+#include "videomodes.h"
+#include "ssd2828.h"
+
+#define SSD2828_DIR 0xB0
+#define SSD2828_VICR1 0xB1
+#define SSD2828_VICR2 0xB2
+#define SSD2828_VICR3 0xB3
+#define SSD2828_VICR4 0xB4
+#define SSD2828_VICR5 0xB5
+#define SSD2828_VICR6 0xB6
+#define SSD2828_CFGR 0xB7
+#define SSD2828_VCR 0xB8
+#define SSD2828_PCR 0xB9
+#define SSD2828_PLCR 0xBA
+#define SSD2828_CCR 0xBB
+#define SSD2828_PSCR1 0xBC
+#define SSD2828_PSCR2 0xBD
+#define SSD2828_PSCR3 0xBE
+#define SSD2828_PDR 0xBF
+#define SSD2828_OCR 0xC0
+#define SSD2828_MRSR 0xC1
+#define SSD2828_RDCR 0xC2
+#define SSD2828_ARSR 0xC3
+#define SSD2828_LCR 0xC4
+#define SSD2828_ICR 0xC5
+#define SSD2828_ISR 0xC6
+#define SSD2828_ESR 0xC7
+#define SSD2828_DAR1 0xC9
+#define SSD2828_DAR2 0xCA
+#define SSD2828_DAR3 0xCB
+#define SSD2828_DAR4 0xCC
+#define SSD2828_DAR5 0xCD
+#define SSD2828_DAR6 0xCE
+#define SSD2828_HTTR1 0xCF
+#define SSD2828_HTTR2 0xD0
+#define SSD2828_LRTR1 0xD1
+#define SSD2828_LRTR2 0xD2
+#define SSD2828_TSR 0xD3
+#define SSD2828_LRR 0xD4
+#define SSD2828_PLLR 0xD5
+#define SSD2828_TR 0xD6
+#define SSD2828_TECR 0xD7
+#define SSD2828_ACR1 0xD8
+#define SSD2828_ACR2 0xD9
+#define SSD2828_ACR3 0xDA
+#define SSD2828_ACR4 0xDB
+#define SSD2828_IOCR 0xDC
+#define SSD2828_VICR7 0xDD
+#define SSD2828_LCFR 0xDE
+#define SSD2828_DAR7 0xDF
+#define SSD2828_PUCR1 0xE0
+#define SSD2828_PUCR2 0xE1
+#define SSD2828_PUCR3 0xE2
+#define SSD2828_CBCR1 0xE9
+#define SSD2828_CBCR2 0xEA
+#define SSD2828_CBSR 0xEB
+#define SSD2828_ECR 0xEC
+#define SSD2828_VSDR 0xED
+#define SSD2828_TMR 0xEE
+#define SSD2828_GPIO1 0xEF
+#define SSD2828_GPIO2 0xF0
+#define SSD2828_DLYA01 0xF1
+#define SSD2828_DLYA23 0xF2
+#define SSD2828_DLYB01 0xF3
+#define SSD2828_DLYB23 0xF4
+#define SSD2828_DLYC01 0xF5
+#define SSD2828_DLYC23 0xF6
+#define SSD2828_ACR5 0xF7
+#define SSD2828_RR 0xFF
+
+#define SSD2828_CFGR_HS (1 << 0)
+#define SSD2828_CFGR_CKE (1 << 1)
+#define SSD2828_CFGR_SLP (1 << 2)
+#define SSD2828_CFGR_VEN (1 << 3)
+#define SSD2828_CFGR_HCLK (1 << 4)
+#define SSD2828_CFGR_CSS (1 << 5)
+#define SSD2828_CFGR_DCS (1 << 6)
+#define SSD2828_CFGR_REN (1 << 7)
+#define SSD2828_CFGR_ECD (1 << 8)
+#define SSD2828_CFGR_EOT (1 << 9)
+#define SSD2828_CFGR_LPE (1 << 10)
+#define SSD2828_CFGR_TXD (1 << 11)
+
+#define SSD2828_VIDEO_MODE_NON_BURST_WITH_SYNC_PULSES (0 << 2)
+#define SSD2828_VIDEO_MODE_NON_BURST_WITH_SYNC_EVENTS (1 << 2)
+#define SSD2828_VIDEO_MODE_BURST (2 << 2)
+
+#define SSD2828_VIDEO_PIXEL_FORMAT_16BPP 0
+#define SSD2828_VIDEO_PIXEL_FORMAT_18BPP_PACKED 1
+#define SSD2828_VIDEO_PIXEL_FORMAT_18BPP_LOOSELY_PACKED 2
+#define SSD2828_VIDEO_PIXEL_FORMAT_24BPP 3
+
+#define SSD2828_LP_CLOCK_DIVIDER(n) (((n) - 1) & 0x3F)
+
+/*
+ * SPI transfer, using the "24-bit 3 wire" mode (that's how it is called in
+ * the SSD2828 documentation). The 'dout' input parameter specifies 24-bits
+ * of data to be written to SSD2828. Returns the lowest 16-bits of data,
+ * that is received back.
+ */
+static u32 soft_spi_xfer_24bit_3wire(const struct ssd2828_config *drv, u32 dout)
+{
+ int j, bitlen = 24;
+ u32 tmpdin = 0;
+ /*
+ * According to the "24 Bit 3 Wire SPI Interface Timing Characteristics"
+ * and "TX_CLK Timing Characteristics" tables in the SSD2828 datasheet,
+ * the lowest possible 'tx_clk' clock frequency is 8MHz, and SPI runs
+ * at 1/8 of that after reset. So using 1 microsecond delays is safe in
+ * the main loop. But the delays around chip select pin manipulations
+ * need to be longer (up to 16 'tx_clk' cycles, or 2 microseconds in
+ * the worst case).
+ */
+ const int spi_delay_us = 1;
+ const int spi_cs_delay_us = 2;
+
+ gpio_set_value(drv->csx_pin, 0);
+ udelay(spi_cs_delay_us);
+ for (j = bitlen - 1; j >= 0; j--) {
+ gpio_set_value(drv->sck_pin, 0);
+ gpio_set_value(drv->sdi_pin, (dout & (1 << j)) != 0);
+ udelay(spi_delay_us);
+ if (drv->sdo_pin != -1)
+ tmpdin = (tmpdin << 1) | gpio_get_value(drv->sdo_pin);
+ gpio_set_value(drv->sck_pin, 1);
+ udelay(spi_delay_us);
+ }
+ udelay(spi_cs_delay_us);
+ gpio_set_value(drv->csx_pin, 1);
+ udelay(spi_cs_delay_us);
+ return tmpdin & 0xFFFF;
+}
+
+/*
+ * Read from a SSD2828 hardware register (regnum >= 0xB0)
+ */
+static u32 read_hw_register(const struct ssd2828_config *cfg, u8 regnum)
+{
+ soft_spi_xfer_24bit_3wire(cfg, 0x700000 | regnum);
+ return soft_spi_xfer_24bit_3wire(cfg, 0x730000);
+}
+
+/*
+ * Write to a SSD2828 hardware register (regnum >= 0xB0)
+ */
+static void write_hw_register(const struct ssd2828_config *cfg, u8 regnum,
+ u16 val)
+{
+ soft_spi_xfer_24bit_3wire(cfg, 0x700000 | regnum);
+ soft_spi_xfer_24bit_3wire(cfg, 0x720000 | val);
+}
+
+/*
+ * Send MIPI command to the LCD panel (cmdnum < 0xB0)
+ */
+static void send_mipi_dcs_command(const struct ssd2828_config *cfg, u8 cmdnum)
+{
+ /* Set packet size to 1 (a single command with no parameters) */
+ write_hw_register(cfg, SSD2828_PSCR1, 1);
+ /* Send the command */
+ write_hw_register(cfg, SSD2828_PDR, cmdnum);
+}
+
+/*
+ * Reset SSD2828
+ */
+static void ssd2828_reset(const struct ssd2828_config *cfg)
+{
+ /* RESET needs 10 milliseconds according to the datasheet */
+ gpio_set_value(cfg->reset_pin, 0);
+ mdelay(10);
+ gpio_set_value(cfg->reset_pin, 1);
+ mdelay(10);
+}
+
+static int ssd2828_enable_gpio(const struct ssd2828_config *cfg)
+{
+ if (gpio_request(cfg->csx_pin, "ssd2828_csx")) {
+ printf("SSD2828: request for 'ssd2828_csx' pin failed\n");
+ return 1;
+ }
+ if (gpio_request(cfg->sck_pin, "ssd2828_sck")) {
+ gpio_free(cfg->csx_pin);
+ printf("SSD2828: request for 'ssd2828_sck' pin failed\n");
+ return 1;
+ }
+ if (gpio_request(cfg->sdi_pin, "ssd2828_sdi")) {
+ gpio_free(cfg->csx_pin);
+ gpio_free(cfg->sck_pin);
+ printf("SSD2828: request for 'ssd2828_sdi' pin failed\n");
+ return 1;
+ }
+ if (gpio_request(cfg->reset_pin, "ssd2828_reset")) {
+ gpio_free(cfg->csx_pin);
+ gpio_free(cfg->sck_pin);
+ gpio_free(cfg->sdi_pin);
+ printf("SSD2828: request for 'ssd2828_reset' pin failed\n");
+ return 1;
+ }
+ if (cfg->sdo_pin != -1 && gpio_request(cfg->sdo_pin, "ssd2828_sdo")) {
+ gpio_free(cfg->csx_pin);
+ gpio_free(cfg->sck_pin);
+ gpio_free(cfg->sdi_pin);
+ gpio_free(cfg->reset_pin);
+ printf("SSD2828: request for 'ssd2828_sdo' pin failed\n");
+ return 1;
+ }
+ gpio_direction_output(cfg->reset_pin, 0);
+ gpio_direction_output(cfg->csx_pin, 1);
+ gpio_direction_output(cfg->sck_pin, 1);
+ gpio_direction_output(cfg->sdi_pin, 1);
+ if (cfg->sdo_pin != -1)
+ gpio_direction_input(cfg->sdo_pin);
+
+ return 0;
+}
+
+static int ssd2828_free_gpio(const struct ssd2828_config *cfg)
+{
+ gpio_free(cfg->csx_pin);
+ gpio_free(cfg->sck_pin);
+ gpio_free(cfg->sdi_pin);
+ gpio_free(cfg->reset_pin);
+ if (cfg->sdo_pin != -1)
+ gpio_free(cfg->sdo_pin);
+ return 1;
+}
+
+/*
+ * PLL configuration register settings.
+ *
+ * See the "PLL Configuration Register Description" in the SSD2828 datasheet.
+ */
+static u32 construct_pll_config(u32 desired_pll_freq_kbps,
+ u32 reference_freq_khz)
+{
+ u32 div_factor = 1, mul_factor, fr = 0;
+ u32 output_freq_kbps;
+
+ /* The intermediate clock after division can't be less than 5MHz */
+ while (reference_freq_khz / (div_factor + 1) >= 5000)
+ div_factor++;
+ if (div_factor > 31)
+ div_factor = 31;
+
+ mul_factor = DIV_ROUND_UP(desired_pll_freq_kbps * div_factor,
+ reference_freq_khz);
+
+ output_freq_kbps = reference_freq_khz * mul_factor / div_factor;
+
+ if (output_freq_kbps >= 501000)
+ fr = 3;
+ else if (output_freq_kbps >= 251000)
+ fr = 2;
+ else if (output_freq_kbps >= 126000)
+ fr = 1;
+
+ return (fr << 14) | (div_factor << 8) | mul_factor;
+}
+
+static u32 decode_pll_config(u32 pll_config, u32 reference_freq_khz)
+{
+ u32 mul_factor = pll_config & 0xFF;
+ u32 div_factor = (pll_config >> 8) & 0x1F;
+ if (mul_factor == 0)
+ mul_factor = 1;
+ if (div_factor == 0)
+ div_factor = 1;
+ return reference_freq_khz * mul_factor / div_factor;
+}
+
+static int ssd2828_configure_video_interface(const struct ssd2828_config *cfg,
+ const struct ctfb_res_modes *mode)
+{
+ u32 val;
+
+ /* RGB Interface Control Register 1 */
+ write_hw_register(cfg, SSD2828_VICR1, (mode->vsync_len << 8) |
+ (mode->hsync_len));
+
+ /* RGB Interface Control Register 2 */
+ u32 vbp = mode->vsync_len + mode->upper_margin;
+ u32 hbp = mode->hsync_len + mode->left_margin;
+ write_hw_register(cfg, SSD2828_VICR2, (vbp << 8) | hbp);
+
+ /* RGB Interface Control Register 3 */
+ write_hw_register(cfg, SSD2828_VICR3, (mode->lower_margin << 8) |
+ (mode->right_margin));
+
+ /* RGB Interface Control Register 4 */
+ write_hw_register(cfg, SSD2828_VICR4, mode->xres);
+
+ /* RGB Interface Control Register 5 */
+ write_hw_register(cfg, SSD2828_VICR5, mode->yres);
+
+ /* RGB Interface Control Register 6 */
+ val = SSD2828_VIDEO_MODE_BURST;
+ switch (cfg->ssd2828_color_depth) {
+ case 16:
+ val |= SSD2828_VIDEO_PIXEL_FORMAT_16BPP;
+ break;
+ case 18:
+ val |= cfg->mipi_dsi_loosely_packed_pixel_format ?
+ SSD2828_VIDEO_PIXEL_FORMAT_18BPP_LOOSELY_PACKED :
+ SSD2828_VIDEO_PIXEL_FORMAT_18BPP_PACKED;
+ break;
+ case 24:
+ val |= SSD2828_VIDEO_PIXEL_FORMAT_24BPP;
+ break;
+ default:
+ printf("SSD2828: unsupported color depth\n");
+ return 1;
+ }
+ write_hw_register(cfg, SSD2828_VICR6, val);
+
+ /* Lane Configuration Register */
+ write_hw_register(cfg, SSD2828_LCFR,
+ cfg->mipi_dsi_number_of_data_lanes - 1);
+
+ return 0;
+}
+
+int ssd2828_init(const struct ssd2828_config *cfg,
+ const struct ctfb_res_modes *mode)
+{
+ u32 lp_div, pll_freq_kbps, pll_config;
+ /* The LP clock speed is limited by 10MHz */
+ const u32 mipi_dsi_low_power_clk_khz = 10000;
+ /*
+ * This is just the reset default value of CFGR register (0x301).
+ * Because we are not always able to read back from SPI, have
+ * it initialized here.
+ */
+ u32 cfgr_reg = SSD2828_CFGR_EOT | /* EOT Packet Enable */
+ SSD2828_CFGR_ECD | /* Disable ECC and CRC */
+ SSD2828_CFGR_HS; /* Data lanes are in HS mode */
+
+ /* Initialize the pins */
+ if (ssd2828_enable_gpio(cfg) != 0)
+ return 1;
+
+ /* Reset the chip */
+ ssd2828_reset(cfg);
+
+ /*
+ * If there is a pin to read data back from SPI, then we are lucky. Try
+ * to check if SPI is configured correctly and SSD2828 is actually able
+ * to talk back.
+ */
+ if (cfg->sdo_pin != -1) {
+ if (read_hw_register(cfg, SSD2828_DIR) != 0x2828 ||
+ read_hw_register(cfg, SSD2828_CFGR) != cfgr_reg) {
+ printf("SSD2828: SPI communication failed.\n");
+ ssd2828_free_gpio(cfg);
+ return 1;
+ }
+ }
+
+ /*
+ * Setup the parallel LCD timings in the appropriate registers.
+ */
+ if (ssd2828_configure_video_interface(cfg, mode) != 0) {
+ ssd2828_free_gpio(cfg);
+ return 1;
+ }
+
+ /* Configuration Register */
+ cfgr_reg &= ~SSD2828_CFGR_HS; /* Data lanes are in LP mode */
+ cfgr_reg |= SSD2828_CFGR_CKE; /* Clock lane is in HS mode */
+ cfgr_reg |= SSD2828_CFGR_DCS; /* Only use DCS packets */
+ write_hw_register(cfg, SSD2828_CFGR, cfgr_reg);
+
+ /* PLL Configuration Register */
+ pll_config = construct_pll_config(
+ cfg->mipi_dsi_bitrate_per_data_lane_mbps * 1000,
+ cfg->ssd2828_tx_clk_khz);
+ write_hw_register(cfg, SSD2828_PLCR, pll_config);
+
+ pll_freq_kbps = decode_pll_config(pll_config, cfg->ssd2828_tx_clk_khz);
+ lp_div = DIV_ROUND_UP(pll_freq_kbps, mipi_dsi_low_power_clk_khz * 8);
+
+ /* VC Control Register */
+ write_hw_register(cfg, SSD2828_VCR, 0);
+
+ /* Clock Control Register */
+ write_hw_register(cfg, SSD2828_CCR, SSD2828_LP_CLOCK_DIVIDER(lp_div));
+
+ /* PLL Control Register */
+ write_hw_register(cfg, SSD2828_PCR, 1); /* Enable PLL */
+
+ /* Wait for PLL lock */
+ udelay(500);
+
+ send_mipi_dcs_command(cfg, MIPI_DCS_EXIT_SLEEP_MODE);
+ mdelay(cfg->mipi_dsi_delay_after_exit_sleep_mode_ms);
+
+ send_mipi_dcs_command(cfg, MIPI_DCS_SET_DISPLAY_ON);
+ mdelay(cfg->mipi_dsi_delay_after_set_display_on_ms);
+
+ cfgr_reg |= SSD2828_CFGR_HS; /* Enable HS mode for data lanes */
+ cfgr_reg |= SSD2828_CFGR_VEN; /* Enable video pipeline */
+ write_hw_register(cfg, SSD2828_CFGR, cfgr_reg);
+
+ return 0;
+}
--- /dev/null
+/*
+ * (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
projects / u-boot / commitdiff