rk3288 Ubuntu nandflash 调试

1、硬件选择 rk nandflash支持列表有的芯片
2、配置uboot ，为二级loader模式： #define CONFIG_SECOND_LEVEL_BOOTLOADER
3、修改内核dts

    &nandc0 {
        status = "okay"; // used nand set "okay" ,used emmc set "disabled"
    };
    &nandc1 {
        status = "disabled"; // used nand set "okay" ,used emmc set "disabled"
    };

    &emmc {
        clock-frequency = <100000000>;
        clock-freq-min-max = <400000 100000000="">;
        supports-highspeed;
        supports-emmc;
        bootpart-no-access;


        supports-DDR_MODE;
        caps2-mmc-hs200;


        ignore-pm-notify;
        keep-power-in-suspend;
        status = "disabled";
    };
    
4、initrd使用
    Rk30xxnand_ko.ko.3.10.0 使用 ，切换到相应版本
5、内核配置项：
    CONFIG_ROCKCHIP_IOVMM  重要
    否则会出现内核插入时错误：
       Unable to handle kernel NULL pointer dereference at virtual address 00000014
[    4.121128] pgd = ed9e8000
[    4.123799] [00000014] *pgd=2da2e831, *pte=00000000, *ppte=00000000
[    4.129999] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
[    4.135302] Modules linked in: rk30xxnand_ko(P+)
[    4.139867] CPU: 1 PID: 127 Comm: insmod Tainted: P             3.10.0 #247
[    4.146707] task: ed820f00 ti: eda50000 task.ti: eda50000
[    4.152018] PC is at disk_alloc_events+0xc/0xd4
[    4.156470] LR is at add_disk+0xb0/0x1d4
[    4.160326] pc : []    lr : []    psr: 60000013
[    4.160326] sp : eda51e98  ip : 00000000  fp : 00000000
[    4.171601] r10: 00000008  r9 : 00000400  r8 : 00000001
[    4.176735] r7 : bf0151a4  r6 : 00000000  r5 : eda18400  r4 : eda18400
[    4.183147] r3 : 00000000  r2 : 0000001f  r1 : eda18440  r0 : eda18400
[    4.189561] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
[    4.196571] Control: 10c5387d  Table: 2d9e806a  DAC: 00000015
[    4.202217]