Re: am335x: system doesn't reboot after flashing NAND

[Sekhar Nori <nsekhar@ti.com>]

On Wednesday 04 June 2014 01:55 PM, Yegor Yefremov wrote:
> On Wed, Jun 4, 2014 at 8:40 AM, Sekhar Nori <nsekhar@ti.com> wrote:
>> On Tuesday 03 June 2014 04:18 PM, Yegor Yefremov wrote:
>>> On Tue, Jun 3, 2014 at 9:57 AM, Yegor Yefremov
>>> <yegorslists@googlemail.com> wrote:
>>>> Kernel: 3.14, 3.15 (I haven't tried another kernels)
>>>>
>>>> As soon as I write something to my NAND flash (via cat image >
>>>> /dev/mtdblockx or ubiupdatevol) and make reboot or press a reset
>>>> button, I see only CCCCC and nothing happens before I make a power
>>>> cycle. Any idea?
>>>
>>> Just forgot to mention, that I was actually booting from MMC (mmc1).
>>> The boot sequence is UART0...XIP...MMC0...NAND.
>>>
>>> If I just mount ubifs partition as rootfs and change some files, I
>>> still can perform reboot and boot from MMC again. The issue seems to
>>> occur only, if I write to /dev/mtdblock directly. What can affect ROM
>>> boot so that it doesn't follow the boot sequence?
>>
>> Writing to sysboot bits in control_status register will make ROM change
>> boot sequence. Not sure why NAND driver should be changing these values.
>> Can you please verify that this register is indeed modified after the
>> NAND write?
> 
> Can I read this register from userspace via debugfs? I can't find such
> entry so far.

If not debugfs you can use devmem2[1] to read from userspace. You need
to provide physical address of the register.

> I made another test: write to NAND and then make kexec. In this case I
> can successfully execute "reboot" afterwards.

Okay. We need to monitor how sysboot values are changing between these
steps.

Thanks,
Sekhar

[1] www.lartmaker.nl/lartware/port/devmem2.c