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List:       linux-omap
Subject:    Re: Tracking N770 breakage
From:       Tony Lindgren <tony () atomide ! com>
Date:       2009-05-23 1:47:18
Message-ID: 20090523014717.GB9283 () atomide ! com
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* Andrew de Quincey <adq@lidskialf.net> [090522 18:39]:
> Quoting Andrew de Quincey <adq_dvb@lidskialf.net>:
>
>> Quoting Andrew de Quincey <adq@lidskialf.net>:
>>
>>> Quoting Andrew de Quincey <adq_dvb@lidskialf.net>:
>>>
>>>> Quoting Tony Lindgren <tony@atomide.com>:
>>>>
>>>>> * Andrew de Quincey <adq_dvb@lidskialf.net> [090519 22:15]:
>>>>>> Quoting Tony Lindgren <tony@atomide.com>:
>>>>>>
>>>>>>> * Andrew de Quincey <adq_dvb@lidskialf.net> [090516 19:17]:
>>>>>>>> Argh, my N770 seems to have just died; it has been behaving slightly
>>>>>>>> oddly and now it simply won't turn on (black screen and no sign of life
>>>>>>>> whatsoever).
>>>>>>>>
>>>>>>>> It is well out of warranty and frankly I don't see myself  
>>>>>>>> buying another
>>>>>>>> one, so this effectively ends my hacking on it :(
>>>>>>>
>>>>>>> Bummer :(
>>>>>>>
>>>>>>> After a quick try, CONFIG_OMAP_RESET_CLOCKS was the first stopper, then
>>>>>>> it could not mount the MMC root.
>>>>>>
>>>>>> Ahh excellent, that was why I posted my progress, in case it rang a bell
>>>>>> with anyone! I think the touchpad driver may be broken as well BTW.
>>>>>>
>>>>>>> I think there was a patch posted for the omap1 MMC by 
>>>>>>> Ladislav few months
>>>>>>> ago that probably fixes it.
>>>>>>
>>>>>> Cool - I hope I may be back in the running soon (I was rather annoyed
>>>>>> when I posted that message!); I've ordered a new battery in case its
>>>>>> just that. A kind person has also offered me one thats broken in a
>>>>>> different way that I can probably cobble together with the remains of
>>>>>> mine if its something more critical that has died.
>>>>>
>>>>> Good to hear, let's hope it just needs a new battery.
>>>>>
>>>>> See also the n8x0 thread. If we get drivers/cbus to mainline, we
>>>>> pretty much have everything we need for 770 in mainline too.
>>>>>
>>>>> It would be nice to get the drivers/mmc/host/omap.c patch integrated
>>>>> for 2.6.30 to make omap1 MMC work again. Ladislav, any news on that?
>>>>
>>>> OK! My friend has lent me his N770 in the meantime so I can get  
>>>> going again. It seems the board is fried on mine as my battery  
>>>> works perfectly fine in his. gah!
>>>>
>>>> Anyway, I have just tried disabling RESET_CLOCKS, but it still  
>>>> doesn't work for me with the very latest linux-omap-2.6.
>>>>
>>>> With my HWA patch applied, at least the screen goes black, but I  
>>>> don't see any console output, and the thing doesn't appear as a  
>>>> USB gadget (I'm mounting NFS as root over USB with cdc_ether).
>>>>
>>>> I wish the thing had an LED I could turn on! Hmm, I wonder if I  
>>>> could turn off the backlight easily..
>>>
>>> Actually, after playing a bit, I discovered I'm getting a boot  
>>> penguin logo ok, but no actual textual console output; weird!
>>
>> I feel really silly; the N770's bootloader had "serial-console"  
>> enabled, which meant all the kernel messages were being sent out that 
>> instead of being displayed on the fb. So I can now see WTF is going on!
>>
>> Next problem for me: ohci-hcd.c is reporting an initialisation error  
>> in the latest kernels, which is why my NFS-over-USB mount fails. I  
>> can't see any changes in the initialisation *values* used, but there  
>> have obviously been the "kill OMAP_TAG_USB" changes; I'm wondering if 
>> its some initialisation ordering problem.
>
> OK got it, it IS a timing problem, due to non-ARM changes in the core  
> kernel (possibly the recent async subsystem startup improvements?).
>
> In the middle of the boot with a recent kernel, I see a message  
> "tahvo-usb: no tahvo_otg_dev" coming from  
> drivers/cbus/tahvo-usb.c/omap_otg_init(). This is because the internal  
> field "tahvo_otg_dev" is NULL. In turn, omap_otg_init() is being called 
> by tahvo_usb_become_peripheral() which is called from higher up in the 
> USB stack.
>
> However, from the code, what is /meant/ to happen is that the "omap_otg" 
> driver is meant to call omap_otg_probe() (which sets that field) before 
> anything calls drivers/cbus/tahvo-usb.c/omap_otg_init(). However, due to 
> the timing problem, it occurs out of sequence, so it thinks there isn't a 
> transceiver present.
>
> tahvo-usb.c looks as though it needs sorting out somehow; it seems to  
> consist of two seperate drivers rammed together, plus it has this timing 
> issue. The tahvo-usb code itself suggests splitting the tahvo-usb driver 
> into an "omap-otg.c" driver, though some thought will be needed to 
> eliminate the timing issue properly.
>

Hmm, a quick diff with $ git diff omap-2.6.28..master drivers/Makefile
shows that cbus order has changed in the Makefile, maybe that causes it?

Tony
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