MPU 8080 read function for iMX28 U-Boot Sitronix ST7789V

[durje]

Hi all,

I am working on a iMX28 platform and my U-Boot LCDIF driver is configured to write to a Sitronix ST7789V display in MPU 8080 mode.

The write function (see below) is working as expected, but I am now trying to create a read function to read the Display ID (RDDID), I've been trying for weeks now and nothing seems to work.

If anyone have already written a similar function or could help me to understand why my function is not working, it would be much appreciated.

Here is the write function (working as expected):

static int mxsfb_write_byte(uint32_t payload, const unsigned int data)
{
	struct mxs_lcdif_regs *regs = (struct mxs_lcdif_regs *)MXS_LCDIF_BASE;
	const unsigned int timeout = 0x10000;
	if (mxs_wait_mask_clr(&regs->hw_lcdif_ctrl_reg, LCDIF_CTRL_RUN,
			      timeout))
		return -ETIMEDOUT;
	writel((1 << LCDIF_TRANSFER_COUNT_V_COUNT_OFFSET) |
		(1 << LCDIF_TRANSFER_COUNT_H_COUNT_OFFSET),
		&regs->hw_lcdif_transfer_count);
	writel(LCDIF_CTRL_DATA_SELECT | LCDIF_CTRL_RUN,
		&regs->hw_lcdif_ctrl_clr);
	if (data)
		writel(LCDIF_CTRL_DATA_SELECT, &regs->hw_lcdif_ctrl_set);
	writel(LCDIF_CTRL_RUN, &regs->hw_lcdif_ctrl_set);
	if (mxs_wait_mask_clr(&regs->hw_lcdif_lcdif_stat_reg, 1 << 29,
			      timeout))
		return -ETIMEDOUT;
	writel(payload, &regs->hw_lcdif_data);
	return mxs_wait_mask_clr(&regs->hw_lcdif_ctrl_reg, LCDIF_CTRL_RUN,
				 timeout);
}

Here is my read function (value is always 0):

static int ReadPara_32Bit(uint32_t *value)
{	
	uint32_t returnValue = 0;
	
	struct mxs_lcdif_regs *regs = (struct mxs_lcdif_regs *)MXS_LCDIF_BASE;
	const unsigned int timeout = 0x10000;
	
	//wait for the RUN to be clear
	if (mxs_wait_mask_clr(&regs->hw_lcdif_ctrl_reg, LCDIF_CTRL_RUN,
			      timeout))
		return -ETIMEDOUT;	
	writel((1 << LCDIF_TRANSFER_COUNT_V_COUNT_OFFSET) |
		(4 << LCDIF_TRANSFER_COUNT_H_COUNT_OFFSET),
		&regs->hw_lcdif_transfer_count);
	
	//Clear the data an run, not sure if it is needed
	writel(LCDIF_CTRL_DATA_SELECT | LCDIF_CTRL_RUN,
		&regs->hw_lcdif_ctrl_clr);
	
	//Set the data flag
	writel(LCDIF_CTRL_DATA_SELECT, &regs->hw_lcdif_ctrl_set);
	
	//change LCDIF from write(default) mode to read mode
	writel(LCDIF_CTRL_READ_WRITEB, &regs->hw_lcdif_ctrl_set);
	
	//Sets RUN to start the transaction
	writel(LCDIF_CTRL_RUN, &regs->hw_lcdif_ctrl_set);
	
	//wait for the RUN to be clear again
	if (mxs_wait_mask_clr(&regs->hw_lcdif_ctrl_reg, LCDIF_CTRL_RUN,
			      timeout))
		return -ETIMEDOUT;

	//Checks that the RX FIFO isn't empty (28_LFIFO_EMPTY)
	//if (mxs_wait_mask_clr(&regs->hw_lcdif_lcdif_stat_reg, 1 << 28, timeout))		return -ETIMEDOUT;

	//Read the value
	returnValue = readl(&regs->hw_lcdif_data);	
	*value = returnValue;
	
	// then set LCDIF to write(default) mode again
	writel(LCDIF_CTRL_READ_WRITEB, &regs->hw_lcdif_ctrl_clr);
	return 0;
}

 And here is how I call the function:

uint32_t rddid = 0;
u16 rddid_cmd = 0x04;
mxsfb_write_byte(rddid_cmd,0);	
int value = ReadPara_32Bit(&rddid);

Thanks in advance for your help.

[durje]

Thank you for the link, unfortunately I couldn't find anything related to the read function to the display.

I'm looking at something similar to this link: https://community.nxp.com/t5/i-MX-Processors/MPU-read-problem-in-iMX28/m-p/249761

Thanks in advance

[igorpadykov]

Hi durje

one can look at L3.14.52_Uboot_mpu_display.patch.zip on

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/Patch-to-support-MPU-8080-LCD-on-iMX6UL-...

Best regards
igor