[U-Boot] No single character output after update to latest u-boot on pandaboard

Chao Xu caesarxuchao at gmail.com
Tue Nov 26 06:02:00 CET 2013 

Thank you! Please see the inline reply.

On Mon, Nov 25, 2013 at 10:40 PM, Lokesh Vutla <lokeshvutla at ti.com> wrote:
> Hi,
> On Tuesday 26 November 2013 09:55 AM, Abraham V. wrote:
>> Hello Chao,
>> (cc R.Sricharan from TI)
>>
>> Quite frankly, I have no idea why your pandaboard fails to  work if
>> CONFIG_SYS_ENABLE_PADS_ALL isn't defined in the omap4_common.h file. From
>> the logs this patch was committed on 13/June/2012 by R.Sricharan. He might
>> have a better explanation so I'm adding him to this discussion. The git log
>> message says this,
> If we enable CONFIG_SYS_ENABLE_PADS_ALL, pin mux for non essential pads for u-boot
> will be configured. Ideally this configuration should be taken care by kernel. This is the main reason
> to remove this config option.
> Due to this reason the following is added to ./doc/feature-removal-schedule.txt
>
> "What:  Remove CONFIG_SYS_ENABLE_PADS_ALL and CONFIG_SYS_CLOCKS_ENABLE_ALL
> When:   Release v2013.07
>
> Why:    When set these options enable "all" of the pads and clocks found
>         on OMAP4/5 platforms, so that the Linux Kernel does not have to.
>         It has been agreed that this goes against the U-Boot design
>         philosophy and since f3f98bb0 we have not enabled more than is
>         used in U-Boot.  The kernel has been updating drivers to enable
>         rather than assume pads/clocks have been enabled already.  Our
>         expectation is that by v2013.07 a suitable kernel shall exist that
>         does not need these options set for a reasonable I/O set to function.
>
> Who:    Tom Rini <trini at ti.com> and Sricharan R <r.sricharan at ti.com>"
>
> Please let me know if I am not clear.
>
The explanation is crystal clear. So the setup of non-essential pins
are left to the kernel. Then do I need to enable any linux kernel
config options to instruct the kernel to take over? I just copied the
old .config from my v3.7 kernel to build v3.12 kernel.
>>
>> "ARM: OMAP4/5: Do not configure non essential pads, clocks, dplls.
>>
>>     Currently on OMAP4/5 platforms, many kernel drivers are dependent
>>     upon the bootloaders for mux, dpll and clock configurations.
>>     This should not be the case and bootloaders should set only the
>>     minimum required for the uboot functionality and kernel boot.
>>
>>     Note that this is going to break the kernel drivers. But this
>>     is the only way to get things fixed in the kernel.
>>
>>     Signed-off-by: R Sricharan <r.sricharan at ti.com>"
>>
>> so I'm curious now. Chao - was your problem that uboot refused to start or
>> were you seeing crashes in the linux kernel? If it's the former, then the
>> kernel doesn't even come into the picture.
> Yes even I am not clear at this point. Chao can you please clarify.
> Ideally the above config will not harm U-Boot to come up on your board.
>
I think it's the uboot refused to start. Because there was no single
character from the serial port. I enabled the early_printk option in
.config and added it to uEnv.txt. After I added the
CONFIG_SYS_CLOCKS_ENABLE_ALL, the board can boot until "Starting
Kernel". I then fixed some other issue of the kernel, like copy the
.dtb to /media/boot, and then kernel booted just fine. I'm curious,
too. Is there anything I can do to further debugging? Thank you both
very much!
> Thanks and regards,
> Lokesh
>>
>> Also, if you could try a simple experiment? Instead of defining that in the
>> common file, could you define it in the omap4_panda.h file and tell us if
>> uboot comes up? ( I'm just hesitant to make changes to a common file if the
>> issue is on only one board)
>>
I will try to do it tmr.
>> Puzzled,
>> Abraham V.
>>
>>
>> On Tue, Nov 26, 2013 at 9:14 AM, Chao Xu <caesarxuchao at gmail.com> wrote:
>>
>>> Hi Abraham,
>>>
>>> I finally got it working by adding "#define
>>> CONFIG_SYS_ENABLE_PADS_ALL" in u-boot/include/configs/omap4_common.h!
>>> This is removed by default in v2013.10. Do you know why? Thank you!
>>>
>>> On Sun, Nov 24, 2013 at 10:11 PM, Abraham V.
>>> <abraham.varricatt at vvdntech.com> wrote:
>>>> Hello Chao,
>>>>
>>>> That sounds odd. Can you try downloading the latest mainline uboot
>>> sources
>>>> and compiling those for your board?
>>>>
>>>> ftp://ftp.denx.de/pub/u-boot/
>>>>
>>>> At least, for the pandaboard I have, the 2013.10 release works well,
>>>> following your instructions. Only difference is that I'm using linaro's
>>>> cross-compiler.
>>>>
>>>> Puzzled,
>>>> Abraham V.
>>>>
>>>>
>>>> On Fri, Nov 22, 2013 at 8:59 PM, Chao Xu <caesarxuchao at gmail.com> wrote:
>>>>>
>>>>> Hi Abraham,
>>>>>
>>>>> Thank you very much for your detailed reply! But I think I can rule
>>>>> out the three possible problems you mentioned.
>>>>> 1. The cross compiler should be fine. Because I use it all the time to
>>>>> compile kernel for pandaboard and it has never been a problem
>>>>> 2. I'm doing exactly what you suggested, i.e. the SD card is
>>>>> partitioned by a pre-built image.
>>>>> 3. The serial cable is fine because the pre-built image was working
>>>>> properly with the serial cable. Only after I update the u-boot comes
>>>>> the no-output problem.
>>>>> Could you think of any other possible problem? I suspect maybe I need
>>>>> to modify other files (uEnv.txt, boot.scr) in the /boot partition?
>>>>> These files came along with the pre-built image. Thanks again.
>>>>>
>>>>> On Fri, Nov 22, 2013 at 3:17 AM, Abraham V.
>>>>> <abraham.varricatt at vvdntech.com> wrote:
>>>>>> My company is designing a custom board that can be thought of as a
>>>>>> derivative of the pandaboard. I believe we have Rev B1 with us in the
>>>>>> office.
>>>>>>
>>>>>> Considering that you are not getting any debug messages on your serial
>>>>>> console, I suspect one of the following;
>>>>>> * your cross-compiler might have issues
>>>>>> * you haven't partitioned the SD card properly
>>>>>> * your serial cable might be damaged.
>>>>>>
>>>>>> Just short the TX and RX lines of your serial cable to test the last
>>>>>> point.
>>>>>> If you can see echo messages, then good, at least the cable is
>>> working.
>>>>>>
>>>>>> Next worry about the partitions - to boot from SD card, the omap4 on
>>> the
>>>>>> pandaboard expects it in a certain format. Try using pre-build
>>> binaries.
>>>>>> For
>>>>>> example;
>>>>>>
>>>>>> http://www.omappedia.com/wiki/Android_Panda_Pre_Built
>>>>>> http://omappedia.org/wiki/Ubuntu_Pre-built_Binaries_Guide
>>>>>>
>>>>>> They have instructions on how to format your SD card. Assuming they
>>>>>> work,
>>>>>> then good! Last point is to check your cross-compiler. Just replace
>>> the
>>>>>> existing MLO and u-boot.bin (or u-boot.img; it depends on what version
>>>>>> you
>>>>>> have) on the SD card with your compiled ones and you'll be in a good
>>>>>> position to narrow down bugs.
>>>>>>
>>>>>> All the best,
>>>>>> Abraham V.
>>>>>>
>>>>>>
>>>>>> On Fri, Nov 22, 2013 at 11:41 AM, Chao Xu <caesarxuchao at gmail.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I'm trying to compile the latest u-boot for my Pandaboard Rev A2. The
>>>>>>> SD card was originally loaded with a working version of 12.04
>>>>>>> linaro-unbunt-developer image. Early printk is enabled in the
>>> original
>>>>>>> image.
>>>>>>>
>>>>>>> I followed this guide (http://elinux.org/Panda_How_to_MLO_%26_u-boot
>>> )
>>>>>>> and here is what I did:
>>>>>>> 1. export ARCH=arm
>>>>>>> 2. export CROSS_COMPILE=arm-linux-gnueabi-
>>>>>>> 3. make omap4_panda_config
>>>>>>> 4.make
>>>>>>> 5. cp MLO u-boot.img /SDCARD/boot/
>>>>>>>
>>>>>>> But when switching on my Panda, there is no output from the serial
>>>>>>> port. And the heartbeat LED is always off. (When every thing works,
>>> it
>>>>>>> is on when booting, and blinks after booting finished).
>>>>>>>
>>>>>>> I don't have any former experience with u-boot. So please let me know
>>>>>>> if there is any more info I should provide.
>>>>>>>
>>>>>>> Any help would be much appreciated! Thank you!
>>>>>>>
>>>>>>> --
>>>>>>> Regards,
>>>>>>> Chao Xu
>>>>>>> _______________________________________________
>>>>>>> U-Boot mailing list
>>>>>>> U-Boot at lists.denx.de
>>>>>>> http://lists.denx.de/mailman/listinfo/u-boot
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Regards,
>>>>> Chao Xu
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Regards,
>>> Chao Xu
>>>
>>
>>
>>
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>>
>



-- 
Regards,
Chao Xu

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