Neoway S720 User manual

LCD Commissioning Guide
Issue 1.0

S720 LCD Commissioning Guide
Copyright
Copyright © Neoway Technology Co., Ltd. All rights reserved.
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Copyright © Neoway Technology Co., Ltd 2022. All rights reserved.
No part of thisdocument may bereproduced or transmitted in any form orby any means withoutprior written
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is the trademark of Neoway Technology Co., Ltd.
All other trademarks and trade names mentioned in this document are the property of their respective
holders.
Notice
This document provides guide for users to use S720.
This document is intended for system engineers (SEs), development engineers, and test engineers.
THIS GUIDE PROVIDES INSTRUCTIONS FOR CUSTOMERS TO DESIGN THEIR APPLICATIONS.
PLEASE FOLLOW THE RULES AND PARAMETERS IN THIS GUIDE TO DESIGN AND COMMISSION.
NEOWAY WILL NOT TAKE ANY RESPONSIBILITY OF BODILY HURT OR ASSET LOSS CAUSED BY
IMPROPER OPERATIONS.
THE INFORMATION IN THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE DUE TO
PRODUCT VERSION UPDATE OR OTHER REASONS.
EVERY EFFORT HAS BEEN MADE IN PREPARATION OF THIS DOCUMENT TO ENSURE ACCURACY
OF THE CONTENTS, BUT ALL STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS
DOCUMENT DO NOT CONSTITUTE A WARRANTY OF ANY KIND, EXPRESS OR IMPLIED.
Neoway provides customers complete technical support. If you have any question, please contact your
account manager or email to the following email addresses:
[email protected]
[email protected]
Website: http://www.neoway.com

S720 LCD Commissioning Guide
Contents
Copyright © Neoway Technology Co., Ltd. All rights reserved.
iii
Contents
1 LCD Architecture Overview .......................................................................5
2 u-boot ........................................................................................................6
2.1 Adding the LCD Driver File........................................................................................................... 6
2.2 Adding Macro Control for LCD Compilation ................................................................................. 7
2.3 Adding LCD Compilation Rules.................................................................................................... 7
3 Modifying the Kernel..................................................................................9
3.1 Adding the LCD Driver File........................................................................................................... 9
3.2 Modifying the LCD Driver File ...................................................................................................... 9
3.3 Referencing the LCD Driver File .................................................................................................11
4 Timing Description ...................................................................................13
4.1 Generating Timing...................................................................................................................... 13
4.2 Confirming Timing ...................................................................................................................... 15

S720 LCD Commissioning Guide
About This Document
Copyright © Neoway Technology Co., Ltd. All rights reserved.
iv
About This Document
Scope
This document is applicable to the S720 series. It describes how to configure the LCD drivers.
Audience
This document is intended for system engineers (SEs), development engineers, and test engineers.
Change History
Issue
Change
Changed By
1.0
Initial draft
Leo Shen
Conventions
Symbol
Indication
Indicates danger or warning. This information must be followed. Otherwise, a
catastrophic module or user device failure or bodily injury may occur.
Indicates caution. This symbol alerts the user to important points about using the
module. If these points are not followed, the module or user device may fail.
Indicates instructions or tips. This symbol provides advices or suggestions that
may be useful when using the module.

S720 LCD Commissioning Guide
Chapter 1 LCD Architecture Overview
Copyright © Neoway Technology Co., Ltd. All rights reserved.
5
1 LCD Architecture Overview
⚫Platform: SL8541E
⚫System: Android 10
⚫LCD: st7703, 720x1280, RGB888, MIPI-4lane
⚫Backlight: PWM + backlight boost chip
The display driver module mainly consists of DPU, DSI, and DPHY. The core module DPU is related
to display and is mainly responsible for layer composition, image transformation, and screen refresh.
The DSI and DPHY are related to communication and are responsible for packaging and transmitting
data. The upper-level program draws the image to be displayed and writes it to the DDR buffer, and
then the DPU retrieves the data from the buffer, synthesizes it, and sends it to the DSI for packaging.
The DPHY sends the packaged data to the panel through the MIPI bus for display, as shown below.
The LCD driver addition process consists of two parts: u-boot and kernel.

S720 LCD Commissioning Guide
Chapter 2 u-boot
Copyright © Neoway Technology Co., Ltd. All rights reserved.
6
2 u-boot
2.1 Adding the LCD Driver File
Step 1: Copy the existing LCD driver file in the following directory:
bsp\bootloader\uboot15\drivers\video\sprd\lcd\
Step 2: Rename the LCD driver file according to the following naming convention. The format is as
follows:
lcd_[DriverIC]_[ModuleVendor]_[BusType]_[Resolution].c
lcd_st7703_rt_mipi_hd_nwy.c
Step 3: Modifying the LCD Driver File
1. Replace all ID-related functions and variable names in the driver file with st7703.
2. Configure the initialization code (provided by the module factory) using the following format:
Step 4: Configure the front and rear porch parameters (the panel_info structure and parameters are
provided by the panel manufacturer), as shown below.

S720 LCD Commissioning Guide
Chapter 2 u-boot
Copyright © Neoway Technology Co., Ltd. All rights reserved.
7
lcd_name is the node name. The lcd dts node name in u-boot and the kernel must be the same, otherwise the
kernel cannot match the correct LCD driver.
Step 5: Implement the panel_ops callback function, as shown below.
static struct panel_ops st7703_ops = {
.init = st7703_init,
.read_id = st7703_readid,
.power = st7703_power,
};
Step 6: Register the panel driver, as shown below.
struct panel_driver st7703_rt_mipi_driver = {
.info = &st7703_info,
.ops = &st7703_ops,
};
2.2 Adding Macro Control for LCD Compilation
After adding and configuring the LCD driver file, you can open the added new LCD module in the board
configuration file.
Take the S720 project as an example. Find the configuration header file of the corresponding project
in u-boot, and add the LCD compilation macro control:
bsp\bootloader\u-boot15\include\configs\S720.h
#define CONFIG_LCD_ST7703_RT_MIPI_HD
2.3 Adding LCD Compilation Rules
Step 1: Modify the LCD Makefile:
u-boot15/drivers/video/sprd/lcd/Makefile
obj-$(CONFIG_LCD_ST7703_RT_MIPI_HD) += lcd_st7703_rt_mipi_hd_nwy.o
Step 2: Modify the LCD configuration file.
// Configure the file path
bsp\bootloader\u-boot15\drivers\video\sprd\lcd\panel_cfg.h
// add the Entrance instructions for the LCD driver

S720 LCD Commissioning Guide
Chapter 2 u-boot
Copyright © Neoway Technology Co., Ltd. All rights reserved.
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#ifdef CONFIG_LCD_ST7703_RT_MIPI_HD
extern struct panel_driver st7703_rt_mipi_driver;
#endif
// Add reference
static struct panel_cfg supported_panel[] = {
#ifdef CONFIG_LCD_ST7703_RT_MIPI_HD
{
.lcd_id = 0x7703,
.drv = &st7703_rt_mipi_driver,
},
#endif
...
}
⚫lcd_id: built-in lcd id, which is used to read the ID to confirm the model.
⚫drv: pointer to the LCD panel driver structure, which points to the driver structure. Associate the
driver structure with supported_panel. During startup, u-boot enumerates the display in this
structure until the readid function of a driver returns success.

S720 LCD Commissioning Guide
Chapter 3 Modifying the Kernel
Copyright © Neoway Technology Co., Ltd. All rights reserved.
9
3 Modifying the Kernel
The configuration of the LCD kernel adopts the new display framework DRM. In the new Android
version, the framework is gradually migrated from ADF to DRM. Starting from the kernel 4.14, the
display framework is gradually migrated to DRM. The panel is now customized through LCD DTS, the
unified SPRD generic panel driver is used, and the modification of the customized driver is currently
not supported.
3.1 Adding the LCD Driver File
1. Copy the existing driver file in the following directory:
bsp\kernel\kernel4.14\arch\arm\boot\dts\lcd\
2. Rename the LCD driver file according to the following naming convention.
For example:
lcd_[DriverIC]_[ModuleVendor]_[BusType]_[Resolution].dtsi
lcd_st7703_rt_mipi_hd_nwy.dtsi
3.2 Modifying the LCD Driver File
Step 1: Rename all the original LCD related names in the old DTSI file. Replace them with
xxx_st7703_xxx.
Step 2: Configure the initialization code (provided by the module factory) using the following format:
Step 3: Configure the DTS attributes.

S720 LCD Commissioning Guide
Chapter 3 Modifying the Kernel
Copyright © Neoway Technology Co., Ltd. All rights reserved.
10
The reference settings are shown below, and the parameters should be consistent with the
configuration on the uboot. The parameters listed in the following table must be configured.
Other parameters can be configured according to the actual situation, or you can consult
Neoway technical support.
Properties
Description
Remarks
lcd_st7703_rt_mipi_hd
LCD node name
It must be consistent with the lcd
name in u-boot, otherwise the kernel
cannot match the correct LCD driver.
sprd,dsi-work-mode
DSI mode used by the LCD to
transmit image data.
Currently, the following values
are supported:
0: cmd mode
1: video burst mode (Default)
2: video non-burst mode with
sync pulse(2)
3: video non-burst mode with
sync event(3)
Confirm the DSI mode based on the
LCD specifications.
Most LCDs use the video mode.
sprd,dsi-lane-number
Total number of data lanes
when the LCD receives the
transmitted video data. The
value ranges from 1 to 4.
Confirm the DSI mode based on the
LCD specifications.
sprd,dsi-color-format
Data format used for video
stream transmission.
Currently, the following
values are supported:
rgb888, rgb666,
rgb666_packed, rgb565,
and dsc.
The default format rgb888.
Confirm the setting based on the
LCD specifications.
sprd,phy-bit-clock
Bit clock, that is, total LCD
data clock
It is calculated and filled by the timing
table.
For details, see Chapter xx.
sprd,reset-on-sequence
Reset sequence before the
LCD is turned on
Confirm the setting based on the
LCD specifications. The sequence is
usually high, low, and high.
sprd,reset-off-sequence
Reset sequence before the
LCD is turned off
Confirm the DSI mode based on the
LCD specifications. The sequence is
usually constant low.
sprd,initial-command
LCD initialization code
It is provided by the module factory
and filled based on the format.
For details, see section 3.2.

S720 LCD Commissioning Guide
Chapter 3 Modifying the Kernel
Copyright © Neoway Technology Co., Ltd. All rights reserved.
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sprd,sleep-in-command
Code that enables the LCD to
enter the sleep mode
Provided by the module
manufacturer
sprd,sleep-out-command
Code that enables the LCD to
exit the sleep mode
Provided by the module
manufacturer
display-timings
Configuration of the MIPI
clock, LCD width and height,
and front and rear porch
parameters
Confirm the setting based on the
LCD specifications.
3.3 Referencing the LCD Driver File
Locate and open the board configuration header file, and associate the LCD driver file that needs to
be adapted with the board through #include.
The file path is as follows:
bsp\kernel\kernel4.14\arch\arm\boot\dts\S720_sl8541e-1h10_32b.dts
Add the LCD header file.
#include "S720_sl8541e.dtsi"
#include "S720_sp9832e-go-mach.dtsi"
#include "S720_sc9832e-wcn.dtsi"
#include "S720_sc2721.dtsi"
#include "S720_sprd-sound-sharkl.dtsi"
#include "lcd/lcd_st7703_rt_mipi_hd_nwy.dtsi"
The panel driver will search for the corresponding LCD child node under the /lcds node based on the
lcd_name uploaded by uboot, so as to complete LCD matching.
&dsi {
status = "okay";
#address-cells = <1>;
#size-cells = <0>;
panel: panel {
compatible = "sprd,generic-mipi-panel";
#address-cells = <1>;
#size-cells = <0>;
reg = <0>;
reset-gpio = <&ap_gpio 50 GPIO_ACTIVE_HIGH>;
sprd,force-attached = "lcd_st7703_rt_mipi_hd";
port {
reg = <1>;
panel_in: endpoint {
remote-endpoint = <&dphy_out>;
};
};

S720 LCD Commissioning Guide
Chapter 3 Modifying the Kernel
Copyright © Neoway Technology Co., Ltd. All rights reserved.
12
};
};

S720 LCD Commissioning Guide
Chapter 4 Timing Description
Copyright © Neoway Technology Co., Ltd. All rights reserved.
13
4 Timing Description
Timing-related parameters, including resolution, front and rear porches, pixel clock, physical clock, are
all related to the display module. Therefore, after replacing the display module with the new one, if the
resolution changes, make sure to notify Neoway technical support.
Timing involves modifications of uboot and kernel. Taking the S720 project as an example:
⚫IC: LCD RuiHeng st7703
⚫Resolution: 720x1280
⚫Bits per Pixel (BPP): RGB888/16.7K color
⚫MIPI: Dsi-4lane
4.1 Generating Timing
Open the Timing calculation table 33340_unisoclcdmipifps-phy_feq calculation_c_v1.05.xlsm, fill
in the parameters such as resolution, front porch, and rear porch, select SC9832E as the platform, and
then adjust the front and rear porches until the desired frame rate is around 60. Note: If there is a
problem with the display, increase or decrease the frame rate appropriately.
⚫hfp = 36
⚫hbp = 36
⚫hsync = 20
⚫vfp = 16
⚫vbp = 14
⚫vsync = 4
Fill the driver parameters such as resolution, front porch, and rear porch in the table, which are marked
in read in the figure below.

S720 LCD Commissioning Guide
Chapter 4 Timing Description
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14
The following two parameters are obtained based on calculation of the table:
⚫phy_feq = 460*1000 // the unit in the code is Kbps.
⚫pixel_clk = 64000000 // the unit in the code is bps
Then fill two clk values into uboot and kernel to verify the effect. The parameter correspondence is as
follows:
uboot:

S720 LCD Commissioning Guide
Chapter 4 Timing Description
Copyright © Neoway Technology Co., Ltd. All rights reserved.
15
static struct panel_info st7703_info = {
/* common parameters */
.lcd_name = "lcd_st7703_rt_mipi_hd",
.type = SPRD_PANEL_TYPE_MIPI,
.bpp = 24,
.width = 720,
.height = 1280,
/* DPI specific parameters */
.pixel_clk = 64000000,
.rgb_timing = {
.hfp = 36,
.hbp = 36,
.hsync = 20,
.vfp = 16,
.vbp = 14,
.vsync = 4,
},
/* MIPI DSI specific parameters */
.phy_freq = 460000, /*Kbps*/
.lane_num = 4,
.work_mode = SPRD_MIPI_MODE_VIDEO,
.burst_mode = PANEL_VIDEO_BURST_MODE,
.nc_clk_en = false,
};
kernel:
/ { lcds {
lcd_st7703_rt_mipi_hd: lcd_st7703_rt_mipi_hd {
sprd,dsi-work-mode = <1>; /* video burst mode */
sprd,dsi-lane-number = <4>;
sprd,dsi-color-format = "rgb888";
sprd,phy-bit-clock = <460000>; /* kbps */
...
display-timings {
timing0 {
clock-frequency = <64000000>;
hactive = <720>;
vactive = <1280>;
hfront-porch = <36>;
hback-porch = <36>;
hsync-len = <20>;
vfront-porch = <16>;
vback-porch = <14>;
vsync-len = <4>;
};
4.2 Confirming Timing
After the above two timing clk values are filled, compiled and configured, confirm timing based on
actual_fps after startup.

S720 LCD Commissioning Guide
Chapter 4 Timing Description
Copyright © Neoway Technology Co., Ltd. All rights reserved.
16
Criterion: The actual frame rate in the table should be consistent with that obtained through cat here.
adb root
adb shell
cat /sys/class/display/dispc0/actual_fps