Platform LCD (MIPI) transplant procedure and problem induction

Original article, original address: http://blog.csdn.net/dearsq/article/details/51210703
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Portingguidebacklight

There are two kinds of hardware designs for backlighting:
1. Built-in parallel backlight
2. External series backlight
for the 1 scenario , the steps are as follows:
1. Transplant the corresponding LCD driver.
2. Set the backlight in U-BOOT\DRIVERS\VIDEO\SPRDFB\SPRDFB_MAIN.C to built-in:
void Set_backlight (uint32_t value) function, add white_led = 1;
3. In Kernel/drivers/video/backlight/sprd_backlight.c's
#if (defined (config_spx15)) front
Delete the following macro definitions, defining only #define Sprd_backlight_whiteled

-- #ifdef CONFIG_BACKLIGHT_SPRD_PWM_MODE--       /*if the backlight is driven by pwm, use this MACRO */--       #define SPRD_BACKLIGHT_PWM-- #else--       /*the backlight is driven by whiteled default */--       #define SPRD_BACKLIGHT_WHITELED--       #define SPRD_DIM_PWM_MODE-- #endif++ #define SPRD_BACKLIGHT_WHITELED

4. In Sprd_bl_whiteled_update_status, delete the following actions:

8| PWM_MOD_MAX);| PWM_ENABLE);

for 2, Spreadtrum is using an external inline, so no configuration is required. However, the loading process of the LCD and Backlight can be understood through the Spreadtrum platform LCD (MIPI) loading process analysis.

LCD

The loading of LCD is divided into two parts, U-boot and Kernel, and the same porting is divided into two parts.

U-boot

1. Add driver files U-boot/drivers/video/sprdfb/lcd/lcd_ek79007_mipi.c
2. Add a compilation rule u-boot/drivers/video/sprdfb/lcd/makefile

        COBJS-$(CONFIG_FB_LCD_EK79007_MIPI) += lcd_ek79007_mipi.o

3. Configure LCD compilation options and LCD size u-boot/include/configs/sp7731gea_hdr.h

4. Associating to Kernel U-BOOT/DRIVERS/VIDEO/SPRDFB_PANEL.C
Add to

Kernel

1. Add driver files Kernel/drivers/video/sprdfb/lcd/lcd_ek79007_mipi.c
Note that the code file needs to be added

2. Add Makefile

        obj-$(CONFIG_FB_LCD_EK79007_MIPI) += lcd_ek79007_mipi.o

3. Add Config Kernel/arch/arm/configs/sp7731gea_hdr-dt_defconfig

        CONFIG_FB_LCD_EK79007_MIPI=y

4. Modify Kconfig

    config FB_LCD_EK79007_MIPI        boolean"support ek79007 mipi panel"        default y

Problems encountered during the debugging process

Q:backlight not Bright
A: Because the use of Spreadtrum's default external series back photoelectric circuit, so the software does not require additional configuration.
Check the hardware:
Check to see if the backlight voltage is

-

-

Check in turn
LCM_BL_PWM output waveform (normal)
LEDA voltage (abnormal) by hardware inspection further found that there is a resistance value of the abnormal (1.3 Kohm mistakenly affixed to 1.3k euro)
After modification, the backlight is normal: white screen .

Q:LCD White screen
A: The transplant should be lit at least (display something, although it may be wrong to display) after the drive is completed
But the actual is white screen (lit backlight only)
Check if the voltage on the screen is normal. To ensure that the voltage is normal for several places:
VGH and VGL

--This place enables the feet to control VGH and VGL

--Found Lcd_pwren received LCM_CABC

And lcm_cabc can't be reused.
So the direct fly line to a high voltage, the Lcd_pwren enables the foot to be high voltage.

Q: When booting, white screen first, then slowly darken (backlight always light)
A: Continue checking the hardware to find that the LCD_VDD does not have an LDO voltage supply.
The solution is from the BUFFER voltage flying line past, with the VDD_1V8, the board width is 2.5mm, can be used normally.
This Kernel section can be displayed normally, but the u-boot stage flower screen.

Q: Grab Log found LCD panel info:720 x, Bit/pix
But actually it should be x 1024, the tracking code finds that Panel Info is output based on the U-BOOT/DRIVERS/VIDEO/SPRDFB/SPRDFB_PANEL.C.

Found and modified in U-boot/include/configs/sp7731gea_hdr.h

And in the burning time to modify the picture of the bootloader stage for 600x1024 BMP
The U-boot stage appears normal.

Original article, original address: http://blog.csdn.net/dearsq/article/details/51210703
Welcome reprint, Reprint please keep the address!

Platform LCD (MIPI) transplant procedure and problem induction