2440 flash驱动的读写以及ECC的实现分析

最新推荐文章于 2023-01-13 14:18:22 发布

原创最新推荐文章于 2023-01-13 14:18:22 发布 · 2k 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#flash #cmd #汇编 #buffer #ext #byte

本文详细介绍了NAND Flash扇区的读写函数实现过程，包括如何确定起始地址、发送命令、等待命令完成等关键步骤，并通过汇编语言处理数据的对齐问题。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

作者：wogoyixikexie@gliet

——————————————————————————————————————————

写 flash 扇区（页）函数

 
 
/*
    @func   BOOL | FMD_WriteSector | Writes the specified data to the specified NAND flash sector/page.
    @rdesc  TRUE = Success, FALSE = Failure.
    @comm    
    @xref   
*/
BOOL FMD_WriteSector(SECTOR_ADDR startSectorAddr, LPBYTE pSectorBuff, PSectorInfo pSectorInfoBuff, DWORD dwNumSectors)
{
    BYTE Status;
    ULONG SectorAddr = (ULONG)startSectorAddr+START_PAGE;//这里确定起始地址 
    ULONG MECC;
    if (!pSectorBuff && !pSectorInfoBuff)
        return(FALSE);
        
    BOOL bLastMode = SetKMode(TRUE);
    NF_nFCE_L();                        // Select the flash chip. 
    NF_WAITRB();                // Wait for flash to complete command. 
    NF_CMD(CMD_RESET);          // Send reset command. 
    NF_WAITRB();                // Wait for flash to complete command. 
    while (dwNumSectors--)
    {//安全确定地址所在位置 
        ULONG blockPage = (((SectorAddr / NAND_PAGE_CNT) * NAND_PAGE_CNT) | (SectorAddr % NAND_PAGE_CNT));
        if (!pSectorBuff)
        {
     // If we are asked just to write the SectorInfo, we will do that separately 
            NF_CMD(CMD_READ2);                      // Send read command. 
            NF_WAITRB();                                // Wait for flash to complete command. 
            NF_CMD(CMD_WRITE);                    // Send write command. 
            NF_ADDR(0);                                 // Column = 0. 
            NF_ADDR(blockPage         & 0xff);          // Page address. 
            NF_ADDR((blockPage >>  8) & 0xff);
            if (NEED_EXT_ADDR)
                NF_ADDR((blockPage >> 16) & 0xff);  
            NF_WAITRB();   // Wait for flash to complete command. 
            WrPageInfo((PBYTE)pSectorInfoBuff);//使用汇编实现的 
            NF_CMD(CMD_WRITE2);     // Send write confirm command. 
            NF_WAITRB();                                // Wait for flash to complete command. 
            do
            {
                NF_CMD(CMD_STATUS);
                Status = NF_RDDATA();                   // Read command status. 
            }while(!(Status & STATUS_READY));
            if (Status & STATUS_ERROR)
            {
                NF_nFCE_H();          // Deselect the flash chip. 
                SetKMode (bLastMode);
                return(FALSE);
            }
            pSectorInfoBuff++;
        }
        else 
        {
            NF_CMD(CMD_READ);                     // Send read command. 
            NF_WAITRB();                                // Wait for flash to complete command. 
            NF_CMD(CMD_WRITE);                    // Send write command. 
            NF_ADDR(0);                                 // Column = 0. 
            NF_ADDR(blockPage         & 0xff);          // Page address. 
            NF_ADDR((blockPage >>  8) & 0xff);
            if (NEED_EXT_ADDR)
                NF_ADDR((blockPage >> 16) & 0xff);  
            NF_WAITRB();                                // Wait for flash to complete command. 
            //  Special case to handle un-aligned buffer pointer. 
            NF_RSTECC();
            NF_MECC_UnLock();
            if( ((DWORD) pSectorBuff) & 0x3) //这个所谓的非对齐是什么意思? 
            {
                WrPage512Unalign (pSectorBuff);//汇编里面已经包含了循环 
            }
            else
            {
                WrPage512(pSectorBuff);         // Write page/sector data. 
            }
    NF_MECC_Lock();//generate ecc 
            
            // Write the SectorInfo data to the media. 
            // 
            if(pSectorInfoBuff)
            {
                WrPageInfo((PBYTE)pSectorInfoBuff);
                pSectorInfoBuff++;
            }
// Make sure we advance the Flash's write pointer (even though we aren't writing the SectorInfo data) 
            else                
           {
                BYTE TempInfo[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
                WrPageInfo(TempInfo);
            }
            //read ECC 
            MECC = NF_RDMECC0();
            NF_WRDATA((UCHAR)((MECC      ) & 0xff));
            NF_WRDATA((UCHAR)((MECC >>  8) & 0xff));
            NF_WRDATA((UCHAR)((MECC >> 16) & 0xff));
            NF_WRDATA((UCHAR)((MECC >> 24) & 0xff));
            //write ecc to spare area 
            NF_CMD(CMD_WRITE2);           // Send write confirm command. 
            NF_WAITRB();                                // Wait for flash to complete command. 
            do
            {
            NF_CMD(CMD_STATUS);
                Status = NF_RDDATA();                   // Read command status. 
            }while(!(Status & STATUS_READY));
            if (Status & STATUS_ERROR)
            {
        NF_nFCE_H();      // Deselect the flash chip. 
                SetKMode (bLastMode);
                return(FALSE);
            }
            pSectorBuff += NAND_PAGE_SIZE;
        }
        ++SectorAddr;
    }
    NF_nFCE_H();                       // Deselect the flash chip. 
    SetKMode (bLastMode);
    
    return(TRUE);
}

读flash 扇区（页）函数和写 flash 扇区（页）函数有点类似，把读和写的ECC比较，看是否正确。

 
  
/*这个函数用于读nandflash的一个扇区
startSectorAddr： nandflash物理扇区的起始地址，对于nandflash来说，就是nandflash中从哪个page开始。 
    
pSectorBuff：扇区数据buffer，从nandflash中读出的每一个扇区的数据都存放在这个buffer中。 
    
pSectorInfoBuff：扇区信息buffer，一般每个扇区的信息会被保存在nandflash的带外数据中，针对小page，带外数据有16 bytes，大page有64 bytes。从nandflash的带外数据将该扇区的相关信息读出来，存放在这个buffer中。 
    
dwNumSectors：读取多少个扇区，对于nandflash来说相当于读取多少个page。 
    
    @func   BOOL | FMD_ReadSector | Reads the specified sector(s) from NAND flash.
    @rdesc  TRUE = Success, FALSE = Failure.
    @comm    
    @xref   
*/
BOOL FMD_ReadSector(SECTOR_ADDR startSectorAddr, LPBYTE pSectorBuff, PSectorInfo pSectorInfoBuff, DWORD dwNumSectors)
{
    ULONG SectorAddr = (ULONG)startSectorAddr +START_PAGE;
    ULONG MECC;
    if (!pSectorBuff && !pSectorInfoBuff)
        return(FALSE);
    BOOL bLastMode = SetKMode(TRUE);
    NF_nFCE_L();                        // Select the flash chip. 
    NF_WAITRB();                        // Wait for flash to complete command. 
    NF_CMD(CMD_RESET);                  // Send reset command. 
    NF_WAITRB();                        // Wait for flash to complete command. 
    
    while (dwNumSectors--)
    {   //为什么还要计算blockPage? 
        //为什么要这么计算? 
        //我明白了，这个SectorAddr所在地方已经超过了一个block，加上后面 
        //是为了算上超过一个page的部分，这样做是为了安全 
        ULONG blockPage = (((SectorAddr / NAND_PAGE_CNT) * NAND_PAGE_CNT) | (SectorAddr % NAND_PAGE_CNT));
        // read spare area 
        if (!pSectorBuff)
        {   
        //read spare area cmd 
            NF_CMD(CMD_READ2);                          // Send read confirm command. 
            NF_WAITRB();                                // Wait for command to complete. 
            NF_ADDR(0);                                 // Column = 0. 
            NF_ADDR(blockPage         & 0xff);          // Page address. 
            NF_ADDR((blockPage >>  8) & 0xff);
            if (NEED_EXT_ADDR)
                NF_ADDR((blockPage >> 16) & 0xff);  
            NF_WAITRB();                                // Wait for command to complete. 
            RdPageInfo((PBYTE)pSectorInfoBuff);         // Read page/sector information.  
            pSectorInfoBuff++;
        }
        
        // read data area 
        else
        {
            NF_CMD(CMD_READ);                           // Send read command. 
            NF_WAITRB();                                // Wait for command to complete. 
            NF_ADDR(0);                                 // Column = 0. 
            NF_ADDR(blockPage         & 0xff);          // Page address. 
            NF_ADDR((blockPage >>  8) & 0xff);
            if (NEED_EXT_ADDR)
                NF_ADDR((blockPage >> 16) & 0xff);  
            NF_WAITRB();                                // Wait for command to complete. 
            //  Handle unaligned buffer pointer 
            // 下面两个函数的控制看手册220page 
            NF_RSTECC();
            NF_MECC_UnLock();
            if( ((DWORD) pSectorBuff) & 0x3) //这个用来干什么? 
            {
                RdPage512Unalign (pSectorBuff);
            }
            else 
            {
                RdPage512(pSectorBuff);                 // Read page/sector data. 
            }
            NF_MECC_Lock();//针对主数据区的校验 
//RdPage512Unalign RdPage512  RdPageInfo这几个都是nand.s的汇编函数 
            if (pSectorInfoBuff)
            {
                RdPageInfo((PBYTE)pSectorInfoBuff);     // Read page/sector information. 
                pSectorInfoBuff ++;
            }
            else
            {
                BYTE TempInfo[8];
                RdPageInfo(TempInfo);                   // Read page/sector information. 
            }
            MECC  = NF_RDDATA() << 0;
            MECC |= NF_RDDATA() << 8;
            MECC |= NF_RDDATA() << 16;
            MECC |= NF_RDDATA() << 24;
            
            //see datasheet page220  
            NF_WRMECCD0( ((MECC&0xff00)<<8)|(MECC&0xff) );
            NF_WRMECCD1( ((MECC&0xff000000)>>8)|((MECC&0xff0000)>>16) );
            
            if (NF_RDESTST0 & 0x3)// if ECC  fail ------main area /spare area bit error 
            {
                RETAILMSG(1,(TEXT("ecc error %x %x /r/n"),NF_RDMECC0(),MECC));
            
                NF_nFCE_H();                            // Deselect the flash chip. 
                SetKMode (bLastMode);
                return FALSE;   
            }            
            pSectorBuff += NAND_PAGE_SIZE;
        }
        ++SectorAddr;
    }
    NF_nFCE_H();                        // Deselect the flash chip. 
    SetKMode (bLastMode);
    return(TRUE);
}

 

——————现在再来看在nand.s实现的汇编函数（注意对齐和非对齐的写法）

if( ((DWORD) pSectorBuff) & 0x3) //这个所谓的非对齐是什么意思?
{
WrPage512Unalign (pSectorBuff);//汇编里面已经包含了循环
}
----------------在汇编nand.s中实现了WrPage512Unalign 函数
LEAF_ENTRY WrPage512Unalign
stmfd sp!,{r1 - r11}

ldr r1, =0xb0e00010 ;NFDATA
mov r2, #480

; Calculate number of unaligned bytes to read (r12 = 4 - (r0 & 3))
and r12, r0, #3
rsb r12, r12, #4
mov r3, r12

wr_unalign1
; Write unaligned bytes
ldrb r4, [r0]
strb r4, [r1]
add r0, r0, #1
subs r3, r3, #1
bne wr_unalign1

wr_main
; Write 480 bytes (32 x 15)
ldmia r0!, {r4 - r11}

str r4, [r1]
str r5, [r1]
str r6, [r1]
str r7, [r1]
str r8, [r1]
str r9, [r1]
str r10,[r1]
str r11,[r1]

subs r2, r2, #32
bne wr_main

; Write 28 bytes
ldmia r0!, {r4 - r10}
str r4, [r1]这个flash是八位的，怎么使用32位的str指令呢？应该是strb才对啊
str r5, [r1]
str r6, [r1]
str r7, [r1]
str r8, [r1]
str r9, [r1]
str r10,[r1]

; Write trailing unaligned bytes
rsbs r12, r12, #4
beq wr_exit

wr_unalign2
ldrb r4, [r0]
strb r4, [r1]
add r0, r0, #1
subs r12, r12, #1
bne wr_unalign2

wr_exit
ldmfd sp!, {r1 - r11}

IF Interworking :LOR: Thumbing
bx lr
ELSE
mov pc, lr ; return
ENDIF

——————————————————————————————————————————

2440的ECC支持2048大页，所以4byte

DATA寄存器很特殊，8位，16位和32位访问都可以，我猜测芯片是把32位访问拆成4个byte分别写4次

非对齐的时候就不能32位访问了，只好strb

——————————————————————————————————————————

引用 4 楼 gooogleman 的回复:
if( ((DWORD) pSectorBuff) & 0x3) //这个所谓的非对齐是什么意思?
{
WrPage512Unalign (pSectorBuff);//这个函数用汇编实现。汇编里面已经包含了循环
}
——日，在这里也要考虑地址对齐问题。

地址对齐是ARM驱动工程师最应该注意的问题。这个真的要小心谨慎。
也欢迎大家来发表意见。

__________________________________________________________-

转载请标明:作者wogoyixikexie@gliet.桂林电子科技大学一系科协，原文地址：http://blog.youkuaiyun.com/gooogleman——如有错误，希望能够留言指出;如果你有更加好的方法，也请在博客后面留言，我会感激你的批评和分享。