2440 flash驱动的读写以及ECC的实现分析

作者：wogoyixikexie@gliet

 

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写 flash 扇区（页）函数

3. /*
4.     @func   BOOL | FMD_WriteSector | Writes the specified data to the specified NAND flash sector/page.
5.     @rdesc  TRUE = Success, FALSE = Failure.
6.     @comm    
7.     @xref   
8. */
9. BOOL FMD_WriteSector(SECTOR_ADDR startSectorAddr, LPBYTE pSectorBuff, PSectorInfo pSectorInfoBuff, DWORD dwNumSectors)
10. {
11.     BYTE Status;
12.     ULONG SectorAddr = (ULONG)startSectorAddr+START_PAGE;//这里确定起始地址
13.     ULONG MECC;
15.     if (!pSectorBuff && !pSectorInfoBuff)
16.         return(FALSE);
17.         
18.     BOOL bLastMode = SetKMode(TRUE);
20.     NF_nFCE_L();                        // Select the flash chip.
21.     NF_WAITRB();                // Wait for flash to complete command.
23.     NF_CMD(CMD_RESET);          // Send reset command.
24.     NF_WAITRB();                // Wait for flash to complete command.
26.     while (dwNumSectors--)
27.     {//安全确定地址所在位置
28.         ULONG blockPage = (((SectorAddr / NAND_PAGE_CNT) * NAND_PAGE_CNT) | (SectorAddr % NAND_PAGE_CNT));
30.         if (!pSectorBuff)
31.         {
32.      // If we are asked just to write the SectorInfo, we will do that separately
33.             NF_CMD(CMD_READ2);                      // Send read command.
34.             NF_WAITRB();                                // Wait for flash to complete command.
36.             NF_CMD(CMD_WRITE);                    // Send write command.
37.             NF_ADDR(0);                                 // Column = 0.
38.             NF_ADDR(blockPage         & 0xff);          // Page address.
39.             NF_ADDR((blockPage >>  8) & 0xff);
40.             if (NEED_EXT_ADDR)
41.                 NF_ADDR((blockPage >> 16) & 0xff);  
42.             NF_WAITRB();   // Wait for flash to complete command.
44.             WrPageInfo((PBYTE)pSectorInfoBuff);//使用汇编实现的
46.             NF_CMD(CMD_WRITE2);     // Send write confirm command.
47.             NF_WAITRB();                                // Wait for flash to complete command.
49.             do
50.             {
51.                 NF_CMD(CMD_STATUS);
52.                 Status = NF_RDDATA();                   // Read command status.
53.             }while(!(Status & STATUS_READY));
55.             if (Status & STATUS_ERROR)
56.             {
57.                 NF_nFCE_H();          // Deselect the flash chip.
58.                 SetKMode (bLastMode);
59.                 return(FALSE);
60.             }
61.             pSectorInfoBuff++;
62.         }
63.         else 
64.         {
65.             NF_CMD(CMD_READ);                     // Send read command.
66.             NF_WAITRB();                                // Wait for flash to complete command.
68.             NF_CMD(CMD_WRITE);                    // Send write command.
69.             NF_ADDR(0);                                 // Column = 0.
70.             NF_ADDR(blockPage         & 0xff);          // Page address.
71.             NF_ADDR((blockPage >>  8) & 0xff);
72.             if (NEED_EXT_ADDR)
73.                 NF_ADDR((blockPage >> 16) & 0xff);  
74.             NF_WAITRB();                                // Wait for flash to complete command.
76.             //  Special case to handle un-aligned buffer pointer.
77.             NF_RSTECC();
78.             NF_MECC_UnLock();
79.             if( ((DWORD) pSectorBuff) & 0x3) //这个所谓的非对齐是什么意思?
80.             {
81.                 WrPage512Unalign (pSectorBuff);//汇编里面已经包含了循环
82.             }
83.             else
84.             {
85.                 WrPage512(pSectorBuff);         // Write page/sector data.
86.             }
87.     NF_MECC_Lock();//generate ecc
88.             
89.             // Write the SectorInfo data to the media.
90.             //
91.             if(pSectorInfoBuff)
92.             {
93.                 WrPageInfo((PBYTE)pSectorInfoBuff);
94.                 pSectorInfoBuff++;
95.             }
96. // Make sure we advance the Flash's write pointer (even though we aren't writing the SectorInfo data)
98.             else                
99.            {
100.                 BYTE TempInfo[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
101.                 WrPageInfo(TempInfo);
102.             }
103.             //read ECC
104.             MECC = NF_RDMECC0();
105.             NF_WRDATA((UCHAR)((MECC      ) & 0xff));
106.             NF_WRDATA((UCHAR)((MECC >>  8) & 0xff));
107.             NF_WRDATA((UCHAR)((MECC >> 16) & 0xff));
108.             NF_WRDATA((UCHAR)((MECC >> 24) & 0xff));
109.             //write ecc to spare area
110.             NF_CMD(CMD_WRITE2);           // Send write confirm command.
111.             NF_WAITRB();                                // Wait for flash to complete command.
113.             do
114.             {
115.             NF_CMD(CMD_STATUS);
116.                 Status = NF_RDDATA();                   // Read command status.
117.             }while(!(Status & STATUS_READY));
119.             if (Status & STATUS_ERROR)
120.             {
121.         NF_nFCE_H();      // Deselect the flash chip.
122.                 SetKMode (bLastMode);
123.                 return(FALSE);
124.             }
125.             pSectorBuff += NAND_PAGE_SIZE;
126.         }
127.         ++SectorAddr;
128.     }
129.     NF_nFCE_H();                       // Deselect the flash chip.
131.     SetKMode (bLastMode);
132.     
133.     return(TRUE);
134. }

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。

3. /*这个函数用于读nandflash的一个扇区
4. 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。 
5.     
6. 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。 
7.     
8. 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。 
9.     
10. dwNumSectors：读取多少个扇区，对于nandflash来说相当于读取多少个page。 
11.     
13.     @func   BOOL | FMD_ReadSector | Reads the specified sector(s) from NAND flash.
14.     @rdesc  TRUE = Success, FALSE = Failure.
15.     @comm    
16.     @xref   
17. */
18. BOOL FMD_ReadSector(SECTOR_ADDR startSectorAddr, LPBYTE pSectorBuff, PSectorInfo pSectorInfoBuff, DWORD dwNumSectors)
19. {
20.     ULONG SectorAddr = (ULONG)startSectorAddr +START_PAGE;
21.     ULONG MECC;
23.     if (!pSectorBuff && !pSectorInfoBuff)
24.         return(FALSE);
26.     BOOL bLastMode = SetKMode(TRUE);
28.     NF_nFCE_L();                        // Select the flash chip.
29.     NF_WAITRB();                        // Wait for flash to complete command.
31.     NF_CMD(CMD_RESET);                  // Send reset command.
32.     NF_WAITRB();                        // Wait for flash to complete command.
33.     
34.     while (dwNumSectors--)
35.     {   //为什么还要计算blockPage?
36.         //为什么要这么计算?
37.         //我明白了，这个SectorAddr所在地方已经超过了一个block，加上后面
38.         //是为了算上超过一个page的部分，这样做是为了安全
39.         ULONG blockPage = (((SectorAddr / NAND_PAGE_CNT) * NAND_PAGE_CNT) | (SectorAddr % NAND_PAGE_CNT));
40.         // read spare area
41.         if (!pSectorBuff)
42.         {   
43.         //read spare area cmd
44.             NF_CMD(CMD_READ2);                          // Send read confirm command.
45.             NF_WAITRB();                                // Wait for command to complete.
47.             NF_ADDR(0);                                 // Column = 0.
48.             NF_ADDR(blockPage         & 0xff);          // Page address.
49.             NF_ADDR((blockPage >>  8) & 0xff);
50.             if (NEED_EXT_ADDR)
51.                 NF_ADDR((blockPage >> 16) & 0xff);  
52.             NF_WAITRB();                                // Wait for command to complete.
54.             RdPageInfo((PBYTE)pSectorInfoBuff);         // Read page/sector information. 
56.             pSectorInfoBuff++;
57.         }
58.         
59.         // read data area
60.         else
61.         {
62.             NF_CMD(CMD_READ);                           // Send read command.
63.             NF_WAITRB();                                // Wait for command to complete.
65.             NF_ADDR(0);                                 // Column = 0.
66.             NF_ADDR(blockPage         & 0xff);          // Page address.
67.             NF_ADDR((blockPage >>  8) & 0xff);
68.             if (NEED_EXT_ADDR)
69.                 NF_ADDR((blockPage >> 16) & 0xff);  
70.             NF_WAITRB();                                // Wait for command to complete.
72.             //  Handle unaligned buffer pointer
73.             // 下面两个函数的控制看手册220page
74.             NF_RSTECC();
75.             NF_MECC_UnLock();
76.             if( ((DWORD) pSectorBuff) & 0x3) //这个用来干什么?
77.             {
78.                 RdPage512Unalign (pSectorBuff);
79.             }
80.             else 
81.             {
82.                 RdPage512(pSectorBuff);                 // Read page/sector data.
83.             }
84.             NF_MECC_Lock();//针对主数据区的校验
85. //RdPage512Unalign RdPage512  RdPageInfo这几个都是nand.s的汇编函数
86.             if (pSectorInfoBuff)
87.             {
88.                 RdPageInfo((PBYTE)pSectorInfoBuff);     // Read page/sector information.
89.                 pSectorInfoBuff ++;
90.             }
91.             else
92.             {
93.                 BYTE TempInfo[8];
94.                 RdPageInfo(TempInfo);                   // Read page/sector information.
95.             }
97.             MECC  = NF_RDDATA() << 0;
98.             MECC |= NF_RDDATA() << 8;
99.             MECC |= NF_RDDATA() << 16;
100.             MECC |= NF_RDDATA() << 24;
101.             
102.             //see datasheet page220 
103.             NF_WRMECCD0( ((MECC&0xff00)<<8)|(MECC&0xff) );
104.             NF_WRMECCD1( ((MECC&0xff000000)>>8)|((MECC&0xff0000)>>16) );
105.             
106.             if (NF_RDESTST0 & 0x3)// if ECC  fail ------main area /spare area bit error
107.             {
108.                 RETAILMSG(1,(TEXT("ecc error %x %x /r/n"),NF_RDMECC0(),MECC));
109.             
110.                 NF_nFCE_H();                            // Deselect the flash chip.
111.                 SetKMode (bLastMode);
112.                 return FALSE;   
113.             }            
114.             pSectorBuff += NAND_PAGE_SIZE;
115.         }
116.         ++SectorAddr;
117.     }
118.     NF_nFCE_H();                        // Deselect the flash chip.
120.     SetKMode (bLastMode);
122.     return(TRUE);
123. }

 

——————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

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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

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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。

 

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