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

Abraham V. abraham.varricatt at vvdntech.com
Tue Nov 26 08:34:17 CET 2013 

I can confirm that the problem is present on the pandaboard Rev B1 version
as well. When Lokesh mentioned the bisect, I checked out mainline and tried
booting from an SD card - it didn't come up. :( removing the lines
mentioned got it working again.

My usual boot device is USB and I use the omap4boot tool for it. Since that
has its own SPL/MLO binary, the only thing I ended up testing was the main
u-boot image. Which works just fine even without the above fix (not too
surprising, since it has nothing to do with SPL).

Befuddled,
Abraham V.




On Tue, Nov 26, 2013 at 12:22 PM, Lokesh Vutla <lokeshvutla at ti.com> wrote:

> Hi Chao,
> On Tuesday 26 November 2013 10:32 AM, Chao Xu wrote:
> > 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.
> No need to enable any config in kernel for this. Your dts should contain
> the required pin mux details.
> I am not sure what is in 3.7 kernel. May be its good to use
> omap2plus_defconfig.
>
> >>>
> >>> "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!
> I think I got the problem.
> I grabbed my panda and tried latest mainline. As you said U-Boot didn't
> come up for me either.
> I did a bisect and verified which patch is causing th issue. Below is the
> patch which breaks omap4.
>
> "6789e84 i2c, omap24xx: convert driver to new mutlibus/mutliadapter
> framework"
> I think because of the linker code added in this patch for
> omap-common/u-boot-spl.lds
>
>         . = ALIGN(4);
>         .u_boot_list : {
>                 KEEP(*(SORT(.u_boot_list*_i2c_*)));
>         } >.sram
>
> If I comment out this code, u-boot comes up as usual.
> Tom/Heiko, can you give a pointer why this is causing the issue.
> Please correct me if I am wrong.
>
> Thanks and regards,
> Lokesh
> >> 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
> >>>>
> >>>
> >>>
> >>>
> >>> _______________________________________________
> >>> U-Boot mailing list
> >>> U-Boot at lists.denx.de
> >>> http://lists.denx.de/mailman/listinfo/u-boot
> >>>
> >>
> >
> >
> >
>
>

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