机型:TCL 55E5690A-3D 机芯方案:MSD6A818 故障现象:不开机 检修经过:通电试机,测量主板各路供电均正常,指示灯亮,二次开机无反应。于是接串口抓群打印如下。根据最后一段:
pc : [<3c600430>] lr : [<3c6693ec>] sp : 3a9fffb8 ip : 0000000a fp : 00000000 r10: 00000000 r9 : 00000001 r8 : 0000000c r7 : 00000004 r6 : 3d3ba1ac r5 : 3c1dd6f8 r4 : 00000000 r3 : 00000083 r2 : 00000060 r1 : 00000000 r0 : 3c6aaf40 Flags: nZCv IRQs off FIQs on Mode UND_32
Undefined instruction........
引起上述错误的原因一般是引导程序在引导系统内核时出现错误,比如加载地址不正确等。但是,从我们维修的角度上讲我们只需要判断出软件的运行程度就可以了, 很显然,此例系统内核没有被正确引导。我们并没有在打印中看到start kernel.因此我们确定,此板引导程序未被正常执行。通常引起这个故障的不是引导程序本身不良, 就是运行引导程序的DDR有问题。根据这个思路本着先软后硬的原则,首先抄写引导程序,写完后开机故障排除。此类案例也遇见过多例DDR问题导致的。分析打印, 有时我们看的并不是打印本身的意思,而是根据打印,判断软件的运行程度,进而确定对应的故障范围。 U-Boot 2011.06-svn2498 (Nov 18 2013 -14:30:55) CPU : Nike Board: BD_MST049B_NIKEU_CUS19 Hello U-Boot DRAM: 468 MiB SPI: Flash is detected (0x0B01, 0xC8, 0x40, 0x15) spi_init: cfg_env_offset: 0x1e0000, at560 uboot held at [3c1ddf60~3d400000] Now running in RAM - U-Boot at: 3c600000 MMC: eMMC 7455MB [E8FFF8h] In: serial Out: serial Err: serial Net: No ethernet found. Get MAC from ethaddr env MAC: 0x40: 0x8b: 0xf6: 0xf6:0x4a: 0xc1 It's the last cmd @@@@@@ u32CpuSpeedMHz= 792 MHz msIR_Initialize Wait for PM51 standby...........PM51 APPbuild code time Oct 18 2013 11:15:01 Lib51 build code time Jul 07 2013 14:25:38 Hello Main _MDrv_PM_PowerDown2Standby UART_115200 [AT][MB][start sb][0] DC_ON AutoDQS0-[456789AB][56789ABC][23456789A][23456789]-[0x5687] AutoDQS1-[56789ABC][56789ABC][23456789A][123456789]-[0x5688] BIST0-OK BIST1-OK _U[AT][MB][start ub][316] U-Boot 2011.06-svn2498 (Nov 18 2013 -14:30:55) CPU : Nike Board: BD_MST049B_NIKEU_CUS19 Hello U-Boot DRAM: 468 MiB SPI: Flash is detected (0x0B01, 0xC8, 0x40, 0x15) spi_init: cfg_env_offset: 0x1e0000, at560 uboot held at [3c1ddf60~3d400000] Now running in RAM - U-Boot at: 3c600000 MMC: eMMC 7455MB [E8FFF8h] In: serial Out: serial Err: serial Net: No ethernet found. Get MAC from ethaddr env MAC: 0x40: 0x8b: 0xf6: 0xf6:0x4a: 0xc1 It's the last cmd @@@@@@ u32CpuSpeedMHz= 792 MHz msIR_Initialize ============= set bootargs===============
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