DM365是的启动方式有两种，通过BOOTSEL[2:0]引脚决定。当其为001时，直接从AEMIF上启动，比如NOR和OneNAND。除此之外
皆是从RBL启动，顺序为RBL-UBL-UBOOT-KERNEL，比如NAND，串口，SD卡等。RBL会搜寻block1到block24去找
UBL，关于RBL启动的详细细节可以参考用户指南关于ARM子系统的那篇文档，很详尽，下面只分析UBL的源码。
UBL源码在PSP包里的board_utilities/flash_utils目录下，主要是COMMON目录和各子平台的目录如DM36x等，内中除了UBL的源码外还有CCS下JTAG的擦除烧写源码，串口烧写源码等(flash_utils\DM36x\CCS下包括NANDWriter和UBL两个文件夹，分别对应针对IPNC的CCS的project)。下面只分析UBL的启动代码。
入门代码是汇编文件start.S，主要是切换操作模式，建立堆栈等，然后跳转到main函数，进入到board_utilities/flash_utils/Common/ubl/src目录下的C文件
ubl.c中。main函数如下：
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// Main entry
point
void
main(void)
{
// Call to real boot function code
LOCAL_boot();
// Jump to entry point
DEBUG_printString("\r\nJumping to entry point at ");
DEBUG_printHexInt(gEntryPoint);
DEBUG_printString(".\r\n");
APPEntry = (void (*)(void)) gEntryPoint; /*UBL结束，gEntryPoint将u-boot入口交给APPEntry*/
(*APPEntry)();
}
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U-boot一般存在于DEVICE_NAND_UBL_SEARCH_START_BLOCK以后块的第0页，ubl试着从
DEVICE_NAND_UBL_SEARCH_START_BLOCK块向后搜索每块的第0页，找到后，前24个字节分别记录着u-boot描述，如入
口函数等
//DM36x/CCS/NANDWriter/src/nandwriter.c nandwriter()函数中
// Fill in
NandBoot header，rxBuf为刚搜到的页
gNandBoot.entryPoint =
*(((Uint32 *)(&rxBuf[4])));/* The first
"long" is entry point for Application ，u-boot主程序将从这里开始执行*/
gNandBoot.numPage = *(((Uint32 *)(&rxBuf[8]))); /* The second "long" is the number of pages
,代码总页数，有多少数据要载入到DDR*/
gNandBoot.block = *(((Uint32 *)(&rxBuf[12]))); /* The third
"long" is the block where Application is stored in NAND */
gNandBoot.page = *(((Uint32 *)(&rxBuf[16]))); /* The fourth "long" is the page number where Application is
stored in NAND */
gNandBoot.ldAddress = *(((Uint32 *)(&rxBuf[20]))); /* The fifth
"long" is the Application load address ,一般情况，程序放在这个地址开始加载*/
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根据以上信息一次读入每一页，然后将u-boot入口传递给gEntryPoint。
main函数主要调用了LOCAL_boot函数来进行实质的引导功能，下面是此函数的内容：
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static Uint32
LOCAL_boot(void)
{
DEVICE_BootMode
bootMode;
// Read boot mode 从BOOTCFG系统寄存器读出，得到目前BOOTSEL[0..2]
bootMode
= DEVICE_bootMode();
if (bootMode == DEVICE_BOOTMODE_UART)
{
// Wait until the RBL is done using the UART.
//对于通过UART启动的，这些代码应该是存在于uart设备上
while((UART0->LSR &
0x40) == 0
);
}
// Platform Initialization
if ( DEVICE_init() != E_PASS ) /*DEVICE_init函数来进行平台的最底层初始化，包括电源域，时钟，DDR，EMIF，UART，I2C，TIMER等*/
{
DEBUG_printString(devString);
DEBUG_printString(" initialization failed!\r\n");
asm(" MOV PC, #0");
}
else
{
DEBUG_printString(devString);
DEBUG_printString(" initialization passed!\r\n");
}
// Set RAM pointer to beginning of RAM
space
UTIL_setCurrMemPtr(0); /*对全局变量currMemPtr赋值*/
// Send some information to host
DEBUG_printString("TI UBL Version: ");
DEBUG_printString(UBL_VERSION_STRING);
DEBUG_printString("\r\nBooting
Catalog Boot Loader\r\nBootMode = ");
// Select Boot Mode
#if defined(UBL_NAND)
{
//Report Bootmode to host
DEBUG_printString("NAND\r\n");
// Copy binary image application from
NAND to RAM
//NANDBOOT_copy()首先打开
NandFlash设备，将NandFlash的硬件信息放在hNandInfo数据结构内。移植ubl时
需要修改与hNandInfo数据结构相关的参数，比如EMIF地址（EMIFStart =
0x02000000 在ubl.cmd;) DEVICE_NAND_CHIP_infoTable结构中的页大小、块数、块中的页数、...
if
(NANDBOOT_copy() != E_PASS)
{
DEBUG_printString("NAND Boot failed.\r\n");
LOCAL_bootAbort();
}
}
#elif defined(UBL_NOR)
{
//Report Bootmode to host
DEBUG_printString("NOR \r\n");
// Copy binary application image from
NOR to RAM
if
(NORBOOT_copy() != E_PASS)
{
DEBUG_printString("NOR Boot failed.\r\n");
LOCAL_bootAbort();
}
}
#elif defined(UBL_SD_MMC)
{
//Report Bootmode to host
DEBUG_printString("SD/MMC \r\n");
// Copy binary of application image
from SD/MMC card to RAM
if (SDMMCBOOT_copy() != E_PASS)
{
DEBUG_printString("SD/MMC Boot failed.\r\n");
LOCAL_bootAbort();
}
}
#else
{
//Report Bootmode to host
DEBUG_printString("UART\r\n");
UARTBOOT_copy();
}
#endif
DEBUG_printString(" DONE");
UTIL_waitLoop(10000);
DEVICE_TIMER0Stop();
return E_PASS;
}
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先通过调用DEVICE_bootMode函数来判断启动方式（通过读取SYS寄存器实现），而后调用了DEVICE_init函数来进行平台的最底层初
始化，包括电源域，时钟，DDR，EMIF，UART，I2C，TIMER等。
而后通过UTIL_setCurrMemPtr函数对全局变量currMemPtr赋值，以后用到。接着通过判断不同的引导方式，采取不同的处理办法，以
NAND启动为例，将调用NANDBOOT_copy函数。此函数将NAND中的某些内容（就是UBOOT）搬移到RAM中，而后
UBL结束，控制权正式交给UBOOT。
看看UBL对平台的初始化，主要是调用了DEVICE_init函数，函数内容如下：
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Uint32 DEVICE_init()
{
Uint32 status = E_PASS;
// Mask all interrupts
AINTC->INTCTL =
0x4;
AINTC->EABASE =
0x0;
AINTC->EINT0 =
0x0;
AINTC->EINT1 =
0x0;
// Clear all interrupts
AINTC->FIQ0 =
0xFFFFFFFF;
AINTC->FIQ1 =
0xFFFFFFFF;
AINTC->IRQ0 =
0xFFFFFFFF;
AINTC->IRQ1 =
0xFFFFFFFF;
#ifndef SKIP_LOW_LEVEL_INIT
POR_RESET();
// System PSC setup - enable all
DEVICE_PSCInit();
DEVICE_pinmuxControl(0,0xFFFFFFFF,0x00FD0000); // All Video
Inputs，Y0-Y7全部作为video in（不作为GPIO），GIO43作为SD1的clk，McBsp开启，MMCSD0关闭
DEVICE_pinmuxControl(1,0xFFFFFFFF,0x00145555); // All Video
Outputs，视频Cout0-Cout7作为色度信号输出使能，场消隐/行消隐同步信号使能，LCD的OE功能关闭
DEVICE_pinmuxControl(2,0xFFFFFFFF,0x000000DA); //
EMIFA，总线使能，但是CE0没有使能，0xDA可能在合众达板子上运行有问题，因为他将ce0设置成GPIO，这样nandflash失效了，我想
可能是TI原版有个cpld，在合众达的测试程序，值为0x55。
DEVICE_pinmuxControl(3,0xFFFFFFFF,0x00180000); // SPI0, SPI1,
UART1, I2C, SD0, SD1, McBSP0, CLKOUTs，串口1使能，其他均作为GPIO，网卡没使能
DEVICE_pinmuxControl(4,0xFFFFFFFF,0x55555555); //SI1-SPI4使能，MMCSD1 使能
GPIO->DIR02
&= 0xfeffffff;
GPIO->CLRDATA02 =
0x01000000;
// System PLL setup
if (status == E_PASS) status |= DEVICE_PLL1Init(PLL1_Mult);
// DDR PLL setup
if (status == E_PASS) status |= DEVICE_PLL2Init();
// DDR2 module setup
if (status == E_PASS) status |= DEVICE_DDR2Init();
#endif
//
AEMIF Setup
if
(status ==
E_PASS) status |= DEVICE_EMIFInit();
//
UART0 Setup
if
(status ==
E_PASS) status |= DEVICE_UART0Init();
//
TIMER0 Setup
if
(status ==
E_PASS) status |= DEVICE_TIMER0Init();
//
I2C0 Setup
if
(status ==
E_PASS) status |= DEVICE_I2C0Init();
return
status;
}
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首先屏蔽和清除中断，然后调用DEVICE_PSCInit函数实现对各模块的电源时钟使能，实质是调用PSC电源时钟管理模块的寄存器实现，函数内容如
下：
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void
DEVICE_PSCInit()
{
unsigned
char i=0;
unsigned char lpsc_start;
unsigned
char lpsc_end,lpscgroup,lpscmin,lpscmax;
unsigned int
PdNum = 0;
lpscmin =0;
lpscmax =2;
for(lpscgroup=lpscmin
; lpscgroup <=lpscmax;
lpscgroup++) {
if(lpscgroup==0)
{
lpsc_start
= 0; //
Enabling LPSC 3 to 28 SCR first
lpsc_end = 28;
}
else if (lpscgroup
== 1) { /* Skip locked LPSCs [29-37] */
lpsc_start
= 38;
lpsc_end = 47;
} else {
lpsc_start
= 50;
lpsc_end = 51;
}
//NEXT=0x3, Enable LPSC's
for(i=lpsc_start; i<=lpsc_end; i++) {
PSC->MDCTL[i] |= 0x3;
}
//Program goctl to start transition
sequence for LPSCs
PSC->PTCMD = (1<<PdNum);
//Wait for GOSTAT = NO TRANSITION from
PSC for Pdomain 0
while(! (((PSC->PTSTAT >> PdNum) & 0x00000001) == 0));
//Wait for MODSTAT = ENABLE from
LPSC's
for(i=lpsc_start; i<=lpsc_end; i++) {
while(!((PSC->MDSTAT[i] & 0x0000001F) == 0x3));
}
}
}
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然后调用DEVICE_pinmuxControl函数决定复用引脚的功能选择，详见数据手册查看引脚功能。
接着调用DM36x/common/src/device.c下的DEVICE_PLL1Init函数实现了PLL1的配置，预分频，倍频，后分频，分频到各个模块，其设置顺序可以参看用户指南ARM子系统文
档，有详细的介绍，PLL2类似，函数内容如下：
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Uint32 DEVICE_PLL1Init(Uint32 PLLMult)
{
unsigned int
CLKSRC=0x0;
unsigned int j;
/*Power up the PLL*/
PLL1->PLLCTL &= 0xFFFFFFFD;
PLL1->PLLCTL
&= 0xFFFFFEFF;
PLL1->PLLCTL |=
CLKSRC<<8;
/*Set
PLLENSRC '0', PLL Enable(PLLEN) selection is controlled through MMR*/
PLL1->PLLCTL &= 0xFFFFFFDF;
/*Set PLLEN=0 => PLL BYPASS MODE*/
PLL1->PLLCTL &= 0xFFFFFFFE;
UTIL_waitLoop(150);
//
PLLRST=1(reset assert)
PLL1->PLLCTL |= 0x00000008;
UTIL_waitLoop(300);
/*Bring PLL out of Reset*/
PLL1->PLLCTL &= 0xFFFFFFF7;
//Program the Multiper and Pre-Divider for PLL1
PLL1->PLLM =
0x51; // VCO will 24*2M/N+1 = 486Mhz
PLL1->PREDIV =
0x8000|0x7;
PLL1->SECCTL =
0x00470000; // Assert TENABLE = 1, TENABLEDIV = 1,
TINITZ = 1
PLL1->SECCTL = 0x00460000;
// Assert TENABLE = 1,
TENABLEDIV = 1, TINITZ = 0
PLL1->SECCTL
= 0x00400000; // Assert TENABLE = 0, TENABLEDIV = 0, TINITZ = 0
PLL1->SECCTL =
0x00410000; // Assert TENABLE = 0, TENABLEDIV = 0,
TINITZ = 1
//Program the PostDiv for PLL1
PLL1->POSTDIV =
0x8000;
// Post divider setting for PLL1
PLL1->PLLDIV2 =
0x8001;
PLL1->PLLDIV3 =
0x8001; // POST DIV 486/2 -> MJCP/HDVICP
PLL1->PLLDIV4 =
0x8003; // POST DIV 486/4 -> EDMA/EDMA CFG
PLL1->PLLDIV5 =
0x8001; // POST DIV 486/2 -> VPSS
PLL1->PLLDIV6 =
0x8011; // 27Mhz POST DIV 486/18 -> VENC
PLL1->PLLDIV7 =
0x8000; // POST DIV 486/2 -> DDR
PLL1->PLLDIV8 =
0x8003; // POST DIV 486/4 -> MMC0/SD0
PLL1->PLLDIV9 =
0x8001; // POST DIV 486/2 -> CLKOUT
UTIL_waitLoop(300);
/*Set the GOSET bit */
PLL1->PLLCMD =
0x00000001; // Go
UTIL_waitLoop(300);
/*Wait for PLL to LOCK */
while(! (((SYSTEM->PLL0_CONFIG) & 0x07000000)
== 0x07000000));
/*Enable the PLL Bit of PLLCTL*/
PLL1->PLLCTL |= 0x00000001; //
PLLEN=0
return
E_PASS;
}
Uint32 DEVICE_PLL2Init()
{
...
// Post divider
setting for PLL2
PLL2->PLLDIV2 = 0x8001; //
594/2 =297 Mhz -> ARM
PLL2->PLLDIV4
= 0x801C; //
POST DIV 594/29 = 20.48 -> VOICE
PLL2->PLLDIV5 =
0x8007;
...
}
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继续在DEVICE_init函数中，下面是调用DEVICE_DDR2Init函数来配置DDR控制器，这是UBL中重要的一部分，如果硬件电路需要更
换内存芯片的话，需要在UBL中修改这个函数，即按照芯片手册来配置DDR控制寄存器中的相关参数，比如时序，BANK数，页大小等。这个函数主要是操作
SYS模块和DDR模块的相关寄存器来配置内存，函数中调用的DEVICE_LPSCTransition函数用来实现模块的电源时钟状态的改变，函数内
容如下：
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Uint32 DEVICE_DDR2Init()
{
DEVICE_LPSCTransition(LPSC_DDR2,0,PSC_ENABLE);
SYSTEM->VTPIOCR = (SYSTEM->VTPIOCR) &
0xFFFF9F3F;
// Set bit CLRZ (bit 13)
SYSTEM->VTPIOCR
= (SYSTEM->VTPIOCR) | 0x00002000;
// Check VTP READY Status
while(
!(SYSTEM->VTPIOCR &
0x8000));
// Set bit VTP_IOPWRDWN bit 14 for DDR
input buffers)
//SYSTEM->VTPIOCR
= SYSTEM->VTPIOCR | 0x00004000;
// Set bit LOCK(bit7) and PWRSAVE
(bit8)
SYSTEM->VTPIOCR = SYSTEM->VTPIOCR
| 0x00000080;
// Powerdown VTP as it is locked (bit
6)
// Set bit
VTP_IOPWRDWN bit 14 for DDR input buffers)
SYSTEM->VTPIOCR
= SYSTEM->VTPIOCR | 0x00004040;
// Wait for calibration to complete
UTIL_waitLoop( 150 );
// Set the DDR2 to synreset, then
enable it again
DEVICE_LPSCTransition(LPSC_DDR2,0,PSC_SYNCRESET);
DEVICE_LPSCTransition(LPSC_DDR2,0,PSC_ENABLE);
DDR->DDRPHYCR = 0x000000C5;
DDR->SDBCR =
0x08D34832; //Program SDRAM Bank Config Register
DDR->SDBCR =
0x0853C832;
DDR->SDTIMR =0x3C934B51; //Program SDRAM Timing Control Register1
DDR->SDTIMR2 =0x4221C72; //Program SDRAM Timing Control Register2
DDR->PBBPR =
0x000000FE;
DDR->SDBCR =
0x08534832; //Program SDRAM Bank Config Register
DDR->SDRCR =
0x00000768; //Program SDRAM Refresh Control
Register
DEVICE_LPSCTransition(LPSC_DDR2,0,PSC_SYNCRESET);
DEVICE_LPSCTransition(LPSC_DDR2,0,PSC_ENABLE);
return
E_PASS;
}
void DEVICE_LPSCTransition(Uint8 module, Uint8 domain,
Uint8 state)
{
// Wait for any outstanding transition to complete
while ( (PSC->PTSTAT) & (0x00000001 << domain) );
// If we are already in that state,
just return
if
(((PSC->MDSTAT[module]) & 0x1F) == state) return;
// Perform transition
PSC->MDCTL[module] = ((PSC->MDCTL[module]) & (0xFFFFFFE0)) | (state);
PSC->PTCMD |= (0x00000001 <<
domain);
// Wait for transition to complete
while ( (PSC->PTSTAT) & (0x00000001 << domain) );
// Wait and verify the state
while (((PSC->MDSTAT[module]) & 0x1F) != state);
}
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而后调用DEVICE_EMIFInit函数来配置EMIF模块，这个模块用来接外存，比如NAND，NOR等。DM365有两个片选空间，如果某一空间
配置成NAND，则需要在寄存器中设置，其函数内容如下：
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Uint32 DEVICE_EMIFInit()
{
AEMIF->AWCCR =
0xff;
AEMIF->A1CR =
0x40400204;
AEMIF->NANDFCR |= 1;
AEMIF->A2CR = 0x00a00505;
return E_PASS;
}
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而后调用DEVICE_UART0Init函数来配置串口0，调用DEVICE_TIMER0Init函数来配置TIMER0，调用
DEVICE_I2C0Init函数来配置I2C控制器，都是操作某一模块的控制寄存器实现，具体如何设置可以参考相关模块的手册，这三个函数的内容如
下：
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Uint32 DEVICE_UART0Init()
{
UART0->PWREMU_MGNT =
0; // Reset UART TX & RX components
UTIL_waitLoop( 100 );
UART0->MDR = 0x0;
UART0->DLL
= 0xd; // Set
baud rate
UART0->DLH = 0;
UART0->FCR =
0x0007; // Clear UART TX & RX FIFOs
UART0->FCR =
0x0000; // Non-FIFO mode
UART0->IER =
0x0007; // Enable interrupts
UART0->LCR =
0x0003; // 8-bit words
// 1 STOP bit generated,
// No Parity, No Stick paritiy,
// No Break control
UART0->MCR =
0x0000; // RTS & CTS disabled,
// Loopback mode disabled,
// Autoflow disabled
UART0->PWREMU_MGNT =
0xE001; // Enable TX & RX componenets
return E_PASS;
}
Uint32
DEVICE_I2C0Init()
{
I2C0->ICMDR = 0;
// Reset I2C
I2C0->ICPSC = 26; // Config prescaler for 27MHz
I2C0->ICCLKL =
20; // Config clk LOW for 20kHz
I2C0->ICCLKH =
20; // Config clk HIGH for 20kHz
I2C0->ICMDR |= I2C_ICMDR_IRS; // Release I2C from reset
return E_PASS;
}
Uint32
DEVICE_TIMER0Init()
{
// Put
timer into reset
TIMER0->EMUMGT_CLKSPD
= 0x00000003;
TIMER0->TCR
= 0x00000000;
// Enable TINT0, TINT1 interrupt
TIMER0->INTCTL_STAT =
0x00000001;
// Set to 64-bit GP Timer mode, enable
TIMER12 & TIMER34
TIMER0->TGCR = 0x00000003;
// Reset timers to zero
TIMER0->TIM12 =
0x00000000;
TIMER0->TIM34 =
0x00000000;
// Set timer period (5 second timeout =
(24000000 * 5) cycles = 0x07270E00)
TIMER0->PRD34 =
0x00000000;
TIMER0->PRD12 =
0x07270E00;
return E_PASS;
}
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至此，DEVICE_init函数结束，程序返回至LOCAL_boot函数中，接着就调用NANDBOOT_copy函数了。
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