MIPI调试小结

mipi接口连接如下(图中没包括供电和复位信号)

三种不同的时序

Non-Burst Mode with Sync Pulses
Non-Burst Mode with Sync Events
Burst Mode (比较常见)

HSS:Horizontal Sync Start
HSE:Horizontal Sync End
HSA:Horizontal Sync Active
VSA:Vertical Sync Active
VSE:Vertical Sync End
VSS:Vertical Sync Start

 

Display Command Set (DCS) 

如0x29开显示，0x28关显示 

LP模式下，命令的类型

写命令分为dcs和generic两种，比较常见的是dcs，如展讯平台的lcd初始化流程

static int sprd_panel_send_cmds(struct mipi_dsi_device *dsi,
				const void *data, int size)
{
	struct sprd_panel *panel;
	const struct dsi_cmd_desc *cmds = data;
	u16 len;

	if ((cmds == NULL) || (dsi == NULL))
		return -EINVAL;

	panel = mipi_dsi_get_drvdata(dsi);

	while (size > 0) {
		len = (cmds->wc_h << 8) | cmds->wc_l;

		if (panel->info.use_dcs)
			mipi_dsi_dcs_write_buffer(dsi, cmds->payload, len);
		else
			mipi_dsi_generic_write(dsi, cmds->payload, len);

		if (cmds->wait)
			msleep(cmds->wait);
		cmds = (const struct dsi_cmd_desc *)(cmds->payload + len);
		size -= (len + 4);
	}

	return 0;
}

/**
 * mipi_dsi_dcs_write_buffer() - transmit a DCS command with payload
 * @dsi: DSI peripheral device
 * @data: buffer containing data to be transmitted
 * @len: size of transmission buffer
 *
 * This function will automatically choose the right data type depending on
 * the command payload length.
 *
 * Return: The number of bytes successfully transmitted or a negative error
 * code on failure.
 */
ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
				  const void *data, size_t len)
{
	struct mipi_dsi_msg msg = {
		.channel = dsi->channel,
		.tx_buf = data,
		.tx_len = len
	};

	switch (len) {
	case 0:
		return -EINVAL;

	case 1:
		msg.type = MIPI_DSI_DCS_SHORT_WRITE;
		break;

	case 2:
		msg.type = MIPI_DSI_DCS_SHORT_WRITE_PARAM;
		break;

	default:
		msg.type = MIPI_DSI_DCS_LONG_WRITE;
		break;
	}

	return mipi_dsi_device_transfer(dsi, &msg);
}


/**
 * mipi_dsi_generic_write() - transmit data using a generic write packet
 * @dsi: DSI peripheral device
 * @payload: buffer containing the payload
 * @size: size of payload buffer
 *
 * This function will automatically choose the right data type depending on
 * the payload length.
 *
 * Return: The number of bytes transmitted on success or a negative error code
 * on failure.
 */
ssize_t mipi_dsi_generic_write(struct mipi_dsi_device *dsi, const void *payload,
			       size_t size)
{
	struct mipi_dsi_msg msg = {
		.channel = dsi->channel,
		.tx_buf = payload,
		.tx_len = size
	};

	switch (size) {
	case 0:
		msg.type = MIPI_DSI_GENERIC_SHORT_WRITE_0_PARAM;
		break;

	case 1:
		msg.type = MIPI_DSI_GENERIC_SHORT_WRITE_1_PARAM;
		break;

	case 2:
		msg.type = MIPI_DSI_GENERIC_SHORT_WRITE_2_PARAM;
		break;

	default:
		msg.type = MIPI_DSI_GENERIC_LONG_WRITE;
		break;
	}

	return mipi_dsi_device_transfer(dsi, &msg);
}

MIPI_DSI_DCS_SHORT_WRITE			= 0x05,
MIPI_DSI_DCS_SHORT_WRITE_PARAM			= 0x15,
MIPI_DSI_DCS_LONG_WRITE				= 0x39,

MIPI_DSI_GENERIC_SHORT_WRITE_0_PARAM		= 0x03,
MIPI_DSI_GENERIC_SHORT_WRITE_1_PARAM		= 0x13,
MIPI_DSI_GENERIC_SHORT_WRITE_2_PARAM		= 0x23,
MIPI_DSI_GENERIC_LONG_WRITE			= 0x29,

如 

05 78 00 01 29
15 00 00 02 41 5A
39 00 00 03 41 5A 03

13 0a 00 01 29
23 00 00 02 FF 01
29 00 00 03 51 FF 00

static ssize_t mipi_dsi_device_transfer(struct mipi_dsi_device *dsi,
					struct mipi_dsi_msg *msg)
{
	const struct mipi_dsi_host_ops *ops = dsi->host->ops;

	if (!ops || !ops->transfer)
		return -ENOSYS;

	if (dsi->mode_flags & MIPI_DSI_MODE_LPM)
		msg->flags |= MIPI_DSI_MSG_USE_LPM;

	return ops->transfer(dsi->host, msg);
}

/**
 * Send a packet on the generic interface
 * @param dsi pointer to structure holding the DSI Host core information
 * @param vc destination virtual channel
 * @param data_type type of command, inserted in first byte of header
 * @param params byte array of command parameters
 * @param param_length length of the above array
 * @return error code
 * @note this function has an active delay to wait for the buffer to clear.
 * The delay is limited to:
 * (param_length / 4) x DSIH_FIFO_ACTIVE_WAIT x register access time
 * @note the controller restricts the sending of .
 * This function will not be able to send Null and Blanking packets due to
 *  controller restriction
 */
int sprd_dsi_wr_pkt(struct sprd_dsi *dsi, u8 vc, u8 type,
			const u8 *param, u16 len)
{
	int i = 0;
	int j = 0;
	u32 payload;
	u8 wc_lsbyte, wc_msbyte;

	if (vc > 3)
		return -EINVAL;

	/* 1st: for long packet, must config payload first */
	if (!dsi_hal_wait_tx_payload_fifo_empty(dsi))
		return -1;
	
	if (len > 2) {
		for (i = 0; i < len; i += j) {
			payload = 0;
			for (j = 0; (j < 4) && ((j + i) < (len)); j++)
				payload |= param[i + j] << (j * 8);

			dsi_hal_set_packet_payload(dsi, payload);
		}
		wc_lsbyte = len & 0xff;
		wc_msbyte = len >> 8;
	} else {
		wc_lsbyte = (len > 0) ? param[0] : 0;
		wc_msbyte = (len > 1) ? param[1] : 0;
	}

	/* 2nd: then set packet header */
	if (!dsi_hal_wait_tx_cmd_fifo_empty(dsi))
		return -EINVAL;

	dsi_hal_set_packet_header(dsi, vc, type, wc_lsbyte, wc_msbyte);

	return 0;
}

static ssize_t sprd_dsi_host_transfer(struct mipi_dsi_host *host,
				const struct mipi_dsi_msg *msg)
{
	struct sprd_dsi *dsi = host_to_dsi(host);
	const u8 *tx_buf = msg->tx_buf;

	if (msg->rx_buf && msg->rx_len) {
		u8 lsb = (msg->tx_len > 0) ? tx_buf[0] : 0;
		u8 msb = (msg->tx_len > 1) ? tx_buf[1] : 0;

		return sprd_dsi_rd_pkt(dsi, msg->channel, msg->type,
				msb, lsb, msg->rx_buf, msg->rx_len);
	}

	if (msg->tx_buf && msg->tx_len)
		return sprd_dsi_wr_pkt(dsi, msg->channel, msg->type,
					tx_buf, msg->tx_len);

	return 0;
}

static const struct mipi_dsi_host_ops sprd_dsi_host_ops = {
	.transfer = sprd_dsi_host_transfer,
};

从lti8998c摘录的dcs写格式

DCSWN-S(DCS write 短包没参数)

DCSW1-S (DCS write 短包一个参数)

DCSW-L(DCS write 长包带参数)

遇到屏幕不显示的情况，可以检查下上电时序(同时确保有电压输出)，配置是否有写错。另外可以使用屏幕的自测模式来排查问题。还有些是硬件问题，比如lcd的fpc不对应，导致信号没有输送到屏幕的引脚，或者fpc接口接触不良(可以尝试按压或者将fpc往前推下)。