CN110737480B

CN110737480B - Serial port driver multiplexing method and device

Info

Publication number: CN110737480B
Application number: CN201910879831.3A
Authority: CN
Inventors: 杨凯
Original assignee: Rockchip Electronics Co Ltd
Current assignee: Rockchip Electronics Co Ltd
Priority date: 2019-09-18
Filing date: 2019-09-18
Publication date: 2022-05-13
Anticipated expiration: 2039-09-18
Also published as: CN110737480A

Abstract

The invention provides a method and a device for multiplexing a serial driver, wherein the method comprises the following steps: running a first starting code in a first starting unit, and acquiring preset configuration parameters to initialize a default serial port; running a second starting code in a second starting unit, judging whether the current required serial port is consistent with the default serial port or not, and if not, re-initializing the current required serial port; and calling an interface function of the first starting unit to perform corresponding operation. Therefore, the serial port is initialized in the early stage of system starting, and only the interface function in the first starting unit needs to be called in the subsequent stage when the printing serial port is needed, so that the repeated initialization of the serial port drive is avoided, the starting time of the whole system is shortened, and the maintenance difficulty of the whole system is reduced.

Description

Serial port driver multiplexing method and device

Technical Field

The invention relates to the field of SOC chip circuits, in particular to a method and a device for multiplexing a serial port driver.

Background

The debugging serial port is a UART port specially used for outputting printing information, and plays an extremely important role in debugging of the embedded system. During the start-up process of the embedded system, various stages are performed, such as BOOT ROM, bootloader, kernel, etc. In the architectures of armv8 and the like, bootloader is further divided into stages of vector loader initialization, ARM trust firmware initialization, trust OS initialization, U-Boot and the like. Each stage is an independent subsystem, and a serial port driver and hardware are respectively required to be initialized and print information is output, so that a developer can know the current starting condition.

Meanwhile, the embedded SOC usually has a plurality of serial ports, and the IO of each serial port may be multiplexed with the IO of other functions, so as to flexibly use different function combinations in different types of products, which results in that the serial ports of the same SOC that can be used for debugging in different projects are different, and each subsystem in the starting process needs to adapt the serial port driver again to enable the print information to be output to the correct serial port. These subsystems are generally maintained by different teams, and some subsystems may not provide source codes to the downstream links of development possibly for security or confidentiality reasons, which brings a challenge to the maintenance of serial port printing drivers which are normally used by adapting to different development boards.

Disclosure of Invention

Therefore, a technical scheme for multiplexing the serial driver is needed to be provided, so that the problems that the serial driver in the prior art is repeatedly initialized and is difficult to maintain in a unified mode are solved.

In order to achieve the above object, the inventor provides a serial driver multiplexing method, including the following steps:

running a first starting code in a first starting unit, and acquiring preset configuration parameters to initialize a default serial port;

running a second starting code in a second starting unit, judging whether the current required serial port is consistent with the default serial port or not, and if not, re-initializing the current required serial port;

and calling an interface function of the first starting unit to perform corresponding operation.

Further, the preset configuration parameters include a base address of the printing debugging serial port and a baud rate required by input and output of the serial port driver.

Further, the interface function of the first starting unit includes an input interface function or an output interface function, and the "calling the interface function of the first starting unit to perform a corresponding operation" includes:

and acquiring a calling instruction of the subsystem, calling an input interface function or an output interface function of the first starting unit, and carrying out printing operation on the output function of the docking subsystem.

Further, the current required serial port is determined according to a current circuit board to which the chip is butted, and the chip is the chip where the first starting unit is located.

Further, the first starting unit is BOOT ROM, and the second starting unit is BOOT loader.

The inventor also provides a serial port driver multiplexing device, which comprises a first starting unit, a parameter storage unit and a plurality of serial ports; the first starting unit stores a first starting code, and the parameter storage unit stores preset configuration parameters; one of the serial ports is a default serial port;

the first boot code when executed implements the steps of:

acquiring preset configuration parameters in a parameter storage unit to initialize a default serial port;

when a second starting code in a second starting unit is operated, judging whether the current required serial port is consistent with the default serial port or not, and if not, initializing the current required serial port again;

and calling the interface function to perform corresponding operation.

The method and the device for multiplexing the serial driver in the technical scheme comprise the following steps: running a first starting code in a first starting unit, and acquiring preset configuration parameters to initialize a default serial port; running a second starting code in a second starting unit, judging whether the current required serial port is consistent with the default serial port or not, and if not, re-initializing the current required serial port; and calling an interface function of the first starting unit to perform corresponding operation. Therefore, the serial port is initialized in the early stage of system starting, and only the interface function in the first starting unit needs to be called in the subsequent stage when the printing serial port is needed, so that the repeated initialization of the serial port drive is avoided, and the whole starting time of the system is shortened. Meanwhile, the serial port configuration is simplified to be maintained by the second starting unit subsystem in a unified mode, and all subsequent subsystems do not need to maintain corresponding drivers and configurations independently, so that the complexity of the maintenance of the whole system is simplified.

Drawings

Fig. 1 is a flowchart of a serial driver multiplexing method according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a serial driver multiplexing apparatus according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a serial driver multiplexing apparatus according to another embodiment of the present invention;

description of reference numerals:

101. a first starting unit;

102. a second starting unit;

103. a serial port;

104. and a parameter storage unit.

Detailed Description

To explain technical contents, structural features, and objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.

The first stage of the SOC start-up process is BOOT ROM, which is a non-modifiable program segment that is solidified inside the chip, and this stage may require printing using a serial port, including an initialization program and an output program required by the serial port. The serial hardware and serial driver used by the subsystems in all subsequent stages are the same as the content used by the BOOT ROM, and the BOOT ROM program is solidified in the chip, does not occupy any system memory, and does not influence the subsequent subsystem program running in any stage of executable spaces such as DRAM memory or NOR. Therefore, as long as the problem that the serial port printing program in the unmodified BOOT ROM is matched with different hardware circuit boards and possibly different serial ports are used is solved, the printing program of the BOOT ROM can be used by all subsystems in the starting process, and the problems of repeated initialization and respective configuration and maintenance of the serial port driver are solved.

To solve the above problem, please refer to fig. 1, which is a flowchart of a serial driver multiplexing method according to an embodiment of the present invention. The method comprises the following steps:

firstly, step S101 is entered to run a first starting code in a first starting unit, and preset configuration parameters are obtained to initialize a default serial port.

In this embodiment, the first BOOT unit is a BOOT ROM, and the first BOOT code is a BOOT program stored in the BOOT ROM. The preset configuration parameters comprise a base address of the printing debugging serial port and a baud rate required by input and output of the serial port driver. The printing debugging serial port refers to a UART controller, namely a Universal Asynchronous Receiver/Transmitter (UART), the UART is a Universal serial data bus used for Asynchronous communication, and the bus is in bidirectional communication and can realize full duplex transmission and reception. The default serial port is a serial port which is automatically configured when the system is started.

The UART is mainly composed of the following parts: the function of each part is as follows:

(1) and an output buffer register for receiving and storing the parallel data from the CPU via the data bus.

(2) And an output shift register which receives the parallel data from the output buffer, shifts out the data bit by bit at the rate of the transmission clock, i.e., converts the parallel data into serial data output.

(3) An input shift register which shifts data appearing on the serial data input line bit by bit at a rate of a reception clock and, when the data is full, supplies the data in parallel to an input buffer register, i.e., converts the serial data into parallel data.

(4) An input buffer register which receives the parallel data from the input shift register and then is taken away by the CPU.

(5) And a control register for receiving the control word from the CPU and determining the transmission mode and data format for communication based on the content of the control word. For example, the parameters such as the asynchronous mode or the synchronous mode, the number of bits of the data character, whether parity exists, and the number of bits of the stop bit.

(6) A status register. The status register stores various status information of the interface, such as whether the output buffer is empty, whether the input character is ready, and the like. During communication, when a certain state is met, state detection logic in the interface sends a corresponding position "1" of the state register for the CPU to query.

And then, step S102 is carried out to run a second starting code in a second starting unit, whether the current required serial port is consistent with the default serial port or not is judged, and if not, the current required serial port is initialized again.

In the boot process, the system may go through different boot stages, that is, after the first boot code in the first boot unit is executed, other boot codes may continue to be executed, for example, the boot code in the second boot unit is executed, and specifically, the second boot code is loaded into a corresponding cache unit (e.g., DDR) to be executed.

In this embodiment, the second starting unit is BOOTLOADER. And determining the current required serial port according to the current circuit board in which the chip is butted, wherein the chip is the chip where the first starting unit is located. The universal SOC main controller can be applied to various blind scenes and is in butt joint with different external devices, a certain fixed serial port can be used as a debugging serial port difficultly, and a proper serial port is required to be selected as the debugging serial port according to an actual circuit board of the external device. The second boot unit Bootloader and the subsequent multi-stage boot codes are stored in an external storage medium, and the storage medium may be one or more of a floppy disk, an optical disk, a DVD, a hard disk, a flash memory, a U disk, a CF card, an SD card, an MMC card, an SM card, a memory stick, an xD card, an eMMC, an SPI flash, an SSD, and a network hard disk.

And then step S103 is entered to call the interface function of the first starting unit to perform corresponding operation.

Because the interface function is solidified in the first starting unit, the interface function can be called repeatedly, and the interface function can not occupy any storage space and program running space outside the SOC when being called.

In this embodiment, the interface function of the first starting unit includes an input interface function or an output interface function, and the corresponding operation includes a printing operation or a reading input operation. The step of calling the interface function of the first starting unit to perform corresponding operation comprises the following steps: and acquiring a calling instruction of the subsystem, calling an input interface function or an output interface function of the first starting unit, and carrying out printing operation on the output function of the docking subsystem. In this embodiment, the subsystems refer to subsystems at different stages during startup, such as a vendor loader, an ARM trust firmware, a trust OS, and a U-Boot, and each subsystem may need to use a print serial port, that is, need to initialize the print serial port. This application is through the input interface function or the output interface function of calling first start unit, come the corresponding required serial ports of having passed through the initialization of butt joint to avoid printing the serial ports and repeated by the initialization, promoted system start efficiency.

As shown in fig. 2, the inventor further provides a serial driver multiplexing apparatus, which includes a first starting unit 101, a parameter storage unit 104, and a plurality of serial ports 103; the first starting unit 101 stores a first starting code, and the parameter storage unit 104 stores a preset configuration parameter; one of the serial ports is a default serial port 103;

the first boot code when executed implements the steps of:

and calling the interface function to perform corresponding operation.

Preferably, the preset configuration parameters include a base address of the printing debugging serial port and a baud rate required by input and output of a serial port driver. And determining the current required serial port according to a current circuit board to which the chip is butted, wherein the chip is the chip where the first starting unit is located. The first starting unit is a BOOT ROM, and the second starting unit is a BOOT loader.

In some embodiments, the interface function of the first boot unit includes an input interface function or an output interface function, and the invoking the interface function of the first boot unit to perform the corresponding operation includes: and acquiring a calling instruction of the subsystem, calling an input interface function or an output interface function of the first starting unit, and carrying out printing operation on the output function of the docking subsystem.

Fig. 3 is a schematic diagram of a serial driver multiplexing apparatus according to another embodiment of the present invention. The SOC chip comprises built-in BOOT ROM, a plurality of UART serial ports, registers and other hardware, wherein the registers are used for driving parameter baud rates required by input and output of serial ports and serial port module base addresses.

Drivers for debugging printing in the BOOT ROM comprise uart _ init (), putc ()/getc (), namely a driver for printing serial ports is contained, and an output/input interface function. The UART _ init () has a function of initializing the UART controller and its IO, the getc () has a function of acquiring an input character from the UART controller, and the putc () has a function of outputting a character from the UART controller. putc ()/getc () is the most basic unit of the standard input and output library, and can interface with any printing function in the C library or the operating system input and output library, such as print (), printf (), printk (), and the like.

In fig. 3, uart base reg and base reg are two registers for storing uart base value and base value. UART base refers to the base address of the UART controller for print debugging, baudrate refers to the baud rate of the UART, and other parameters generally use 8 data bits and 1 stop bit as default configuration without additional modification. In a standard NS16550 or similar drive, baudrates may be continuously used after configuration of registers of the UART controller. The input and output character program is realized by reading and writing a register with fixed offset in the UART controller, so the putc ()/getc () program needs to be associated with UART base to realize the reading and writing of characters for different UART controllers.

The UART0/1/2 in fig. 3 refers to 3 UART controllers, and the specific number is not limited, and may be less than 3 or more than 3. The Subsystem 1/2/3 referred to in the right column of fig. 3 refers to independent subsystems required at different stages of the BOOT ROM in the SoC BOOT process, and may be modules of a manufacturer such as loader, ARM-managed Firmware, Trust OS, U-BOOT, Kernel, and the like, and the number is not limited to 3.

After the system is started, a start code in the BOOTROM initializes a serial port (i.e., work executed by a uart _ init () function) according to a default configuration (default values stored in uart base and base registers), and then uses putc () and getc () interfaces according to actual conditions, i.e., according to call requests of subsystems in different phases, the print () related functions of the subsystems are docked through the putc () and getc () interfaces.

After the BOOT ROM stage is completed, the UART controller and its IO are reinitialized according to the debugging serial number used by the actual circuit board (i.e., the circuit board of the aforementioned electronic component connected to the SOC) in the Subsystem 1 (some manufacturers refer to First Loader or other names) (the reinitialization is not required if the serial number used is consistent with the default serial number of the chip), and the putc ()/getc () interface of the BOOT ROM is directly used in the subsequent program.

In the subsequent subsystem at any starting stage, the serial port does not need to be initialized any more, and when the serial port needs to be used for printing, a putc ()/getc () interface provided by the BOOT ROM can be directly called, and printing operation is carried out through a print () related function of the docking subsystem.

The invention provides a method and a device for multiplexing a serial driver, wherein the method comprises the following steps: running a first starting code in a first starting unit, and acquiring preset configuration parameters to initialize a default serial port; running a second starting code in a second starting unit, judging whether the current required serial port is consistent with the default serial port or not, and if not, re-initializing the current required serial port; and calling the interface function of the first starting unit to perform corresponding operation. Therefore, the serial port is initialized in the early stage of system starting, and only the interface function in the first starting unit needs to be called in the subsequent stage when the printing serial port is needed, so that the repeated initialization of the serial port drive is avoided, and the whole starting time of the system is shortened. Meanwhile, the scheme can also reduce the repeated maintenance work of different subsystems of the printing serial port driver in the starting stage, improve the usability of the system and reduce the system maintenance work.

It should be noted that, although the above embodiments have been described herein, the invention is not limited thereto. Therefore, based on the innovative concepts of the present invention, the technical solutions of the present invention can be directly or indirectly applied to other related technical fields by making changes and modifications to the embodiments described herein, or by using equivalent structures or equivalent processes performed in the content of the present specification and the attached drawings, which are included in the scope of the present invention.

Claims

1. A method for multiplexing serial drivers is characterized by comprising the following steps:

running a second starting code in a second starting unit, judging whether the current required serial port is consistent with the default serial port or not, and if not, re-initializing the current required serial port; the first starting unit is a BOOT ROM, and the second starting unit is a BOOT loader;

acquiring a calling instruction of the subsystem, calling a getc input interface function or a putc output interface function of the first starting unit, and carrying out printing operation on a print output function of the subsystem; the subsystems refer to subsystems in different stages during starting.

2. The method for multiplexing the serial driver as claimed in claim 1, wherein the preset configuration parameters include a base address of a print debug serial port and a baud rate required for input and output of the serial driver.

3. The method for multiplexing the serial port driver as claimed in claim 1, wherein the current required serial port is determined according to a circuit board to which a current chip is docked, and the chip is the chip where the first starting unit is located.

4. A serial port driver multiplexing device is characterized by comprising a first starting unit, a parameter storage unit and a plurality of serial ports; the first starting unit stores a first starting code, and the parameter storage unit stores preset configuration parameters; one of the serial ports is a default serial port;

the first boot code when executed implements the steps of:

when a second starting code in a second starting unit is operated, judging whether the current required serial port is consistent with the default serial port or not, and if not, initializing the current required serial port again; the first starting unit is a BOOT ROM, and the second starting unit is a BOOT loader;

5. The device as claimed in claim 4, wherein the preset configuration parameters include a base address of the print debug serial port and a baud rate required for the input and output of the serial port driver.

6. The serial port driver multiplexing device according to claim 4, wherein the current required serial port is determined according to a circuit board to which a current chip is docked, and the chip is the chip on which the first starting unit is located.