Re: [Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[Luke Kenneth Casson Leighton]

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Tue, Apr 18, 2017 at 10:22 PM,   wrote:
> On  Thu, 6 Apr 2017 06:12:16 +0100
> Luke Kenneth Casson Leighton  wrote:
>> ok so the story goes like this:
>>
>> back in august 2016 i got the A20 card up and running with mainline
>> 4.7rc1 (or thereabouts), including patching in NAND support for a
>> proper mtd device.  it worked... up to a point... except when u-boot
>> did a complete scan it CORRUPTED the NAND flash... just from reads.
>>
>> i figured this was "just software" as it's pretty experimental, and
>> the 3.4.104 sunxi-nand works perfectly.
>>
>> fast-foward to a few months ago, when i was testing the external
>> micro-sd slot, weirdly it resulted in a kernel segfault *from the
>> sunxi-nand driver*.  i thought, "that's weird, might be to do with
>> current-fighting from the micro-desktop PCB not having level-shifting"
>>
>> sooo... that's now fixed: the micro-sd slot works perfectly through
>> the new revision 1.7 microdesktop's level-shifting IC.  however i got
>> exactly the same kernel segfault in the sunxi-nand driver, so i
>> temporarily took it out of the kernel config, tested again, and yes,
>> the micro-sd worked fine.
>>
>> ... except that when i booted it up again, the nand flash had been
>> corrupted.  now, bear in mind there's *NO DRIVER INSTALLED*.
>>
>> this is just too weird for me to deal with.  not to mention, because
>> of the age of the A20's Boot ROM there is now a limited set of
>> "legacy" NAND ICs available i've had it with them.
>>
> 
>
> I'm sorry to hear you are having trouble.
> Personally, I like the super weird Linux problems. Can I have one of
> those malfunctioning alpha boards to try to figure out what's going on?
> I grant you that I've never worked on something quite this low level
> before, so I won't be solving it any time soon, but it would be worth
> looking into just so that we don't have this problem again (yes, I would
> like to learn how to create SBCs).

 sure - once i have working prototypes to replace it with.

l.

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[Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[doark]

On  Thu, 6 Apr 2017 06:12:16 +0100
Luke Kenneth Casson Leighton  wrote:
> ok so the story goes like this:
> 
> back in august 2016 i got the A20 card up and running with mainline
> 4.7rc1 (or thereabouts), including patching in NAND support for a
> proper mtd device.  it worked... up to a point... except when u-boot
> did a complete scan it CORRUPTED the NAND flash... just from reads.
> 
> i figured this was "just software" as it's pretty experimental, and
> the 3.4.104 sunxi-nand works perfectly.
> 
> fast-foward to a few months ago, when i was testing the external
> micro-sd slot, weirdly it resulted in a kernel segfault *from the
> sunxi-nand driver*.  i thought, "that's weird, might be to do with
> current-fighting from the micro-desktop PCB not having level-shifting"
> 
> sooo... that's now fixed: the micro-sd slot works perfectly through
> the new revision 1.7 microdesktop's level-shifting IC.  however i got
> exactly the same kernel segfault in the sunxi-nand driver, so i
> temporarily took it out of the kernel config, tested again, and yes,
> the micro-sd worked fine.
> 
> ... except that when i booted it up again, the nand flash had been
> corrupted.  now, bear in mind there's *NO DRIVER INSTALLED*.
> 
> this is just too weird for me to deal with.  not to mention, because
> of the age of the A20's Boot ROM there is now a limited set of
> "legacy" NAND ICs available i've had it with them.
> 


I'm sorry to hear you are having trouble.
Personally, I like the super weird Linux problems. Can I have one of
those malfunctioning alpha boards to try to figure out what's going on?
I grant you that I've never worked on something quite this low level
before, so I won't be solving it any time soon, but it would be worth
looking into just so that we don't have this problem again (yes, I would
like to learn how to create SBCs).

Thanks,
David

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Re: [Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[zap]

On 04/06/2017 07:05 PM, Luke Kenneth Casson Leighton wrote:
> ---
> crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
>
>
> On Thu, Apr 6, 2017 at 5:38 PM, Vincent Legoll  
> wrote:
>>>  basic logical reasoning says: remove the NAND IC.
>> Yes, stop the madness, make it work as-is/as-you-can,
>> and keep the fancy for V2 :-)
>>
>> Half-joke aside, I'm with you, get it out the door and take
>> a break.
>>
>> If I undestand, the V2 may not even be A20-based...
>  slight misunderstanding: i'm working on a second card that happens to
> have an RK3288 processor, named EOMA68-RK3288, current revision 0.1.
> that cannot be called "V2" i.e. is totally separate and distinct from
> the card named EOMA68-A20, current revision 2.7.4
I am sure you will succeed in reverse engineering all the blobs out. and
once you do, I will most definitely buy one and laptop casing.  and if
you want I will donate an extra 30$ because I didn't buy the original
a20.

He does indeed have a point though, once you get it out the door take a
break. You deserve it. :)

> l.
>
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Re: [Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[Luke Kenneth Casson Leighton]

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Thu, Apr 6, 2017 at 5:38 PM, Vincent Legoll  wrote:
>>  basic logical reasoning says: remove the NAND IC.
>
> Yes, stop the madness, make it work as-is/as-you-can,
> and keep the fancy for V2 :-)
>
> Half-joke aside, I'm with you, get it out the door and take
> a break.
>
> If I undestand, the V2 may not even be A20-based...

 slight misunderstanding: i'm working on a second card that happens to
have an RK3288 processor, named EOMA68-RK3288, current revision 0.1.
that cannot be called "V2" i.e. is totally separate and distinct from
the card named EOMA68-A20, current revision 2.7.4

l.

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Re: [Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[Luke Kenneth Casson Leighton]

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Thu, Apr 6, 2017 at 1:38 PM, Joseph Honold  wrote:
> On 04/06/2017 12:12 AM, Luke Kenneth Casson Leighton wrote:
>> now, i _could_ convert to eMMC but it's too much of a major redesign:
>> it involves disrupting the RGB/TTL tracks, and may require at least
>> two more rounds of pre-production prototyping...
>>
>> ... it's too much: it's too risky... and i'm getting fed up.  so.
>> what i'm going to do instead is: cut the NAND IC entirely, then wire
>> SDC2 (which is the same pins as the NAND) to the *ON-BOARD* Micro-SD
>> card slot, instead.
>
> Not that I'm against dual SD slots, but from what I see, NAND and eMMC
> share the same pins so it should be easy enough to add the bga
> footprint and the required passives.

 should... but (a) if i get it wrong it's yet another $1500-$2000 and
yet another 8 week delay, which means that it could be $3000-$4000 and
16 weeks because it will be necessary to do *two* more revisions, one
to find out that the PCB design was wrong and one to add corrections

 and (b) yes the same wires can be used but no the boot order cannot
be changed because as it's the exact same wires there's still no room
to cross over MMC3 and MMC0 to make MMC0 the "on-board" boot and MMC3
the EOMA68 off-board microsd.

 the other alternative is to turn the A20 round by 90 degrees and to
use two DDR3x16 RAM ICs instead of four DDR3x8 RAM ICs.

 howevver...

 (a) the cost of 2x DDR3x16 RAM ICs to make up 2GB is a COMPLETELY
INSANE $20 just for the memory alone.

 (b) replacing the memory layout and adjusting the power management is
basically a total redesign of the board, i might as well chuck the
ENTIRE design away and start completely from scratch.

i estimate that would take about three revisions, thus would be
somewhere between $4,500-$6,000 and take an estimated 10-12 weeks.

 and it'll be a $40 PCB.  which there isn't enough cash for.

 basic logical reasoning says: remove the NAND IC.

l.

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Re: [Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[Joseph Honold]

On 04/06/2017 12:12 AM, Luke Kenneth Casson Leighton wrote:
> now, i _could_ convert to eMMC but it's too much of a major redesign:
> it involves disrupting the RGB/TTL tracks, and may require at least
> two more rounds of pre-production prototyping...
> 
> ... it's too much: it's too risky... and i'm getting fed up.  so.
> what i'm going to do instead is: cut the NAND IC entirely, then wire
> SDC2 (which is the same pins as the NAND) to the *ON-BOARD* Micro-SD
> card slot, instead.

Not that I'm against dual SD slots, but from what I see, NAND and eMMC
share the same pins so it should be easy enough to add the bga
footprint and the required passives.

The MarsBoard A20 has pads for both NAND and eMMC in the same
footprint so you can use one or the other without losing board space.

http://www.haoyuelectronics.com/service/A10-A20/Schematics/CM-A10/

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Re: [Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[David Boddie]

On Thu Apr 6 06:12:16 BST 2017, Luke Kenneth Casson Leighton wrote:

> ... it's too much: it's too risky... and i'm getting fed up. so.
> what i'm going to do instead is: cut the NAND IC entirely, then wire
> SDC2 (which is the same pins as the NAND) to the *ON-BOARD* Micro-SD
> card slot, instead.
> 
> what that will give is *two* bootable Micro-SD card options, priority
> being first the external one (MMC0) and second the on-board one
> (MMC2).

I can't comment on the technical issues but I think this is an improvement in
terms of usability, at least from my experience using other systems that
relied on booting from Micro-SD instead of from NAND flash.

David

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[Arm-netbook] microdesktop v1.7 arrived, works fine... but...

[Luke Kenneth Casson Leighton]

ok so the story goes like this:

back in august 2016 i got the A20 card up and running with mainline
4.7rc1 (or thereabouts), including patching in NAND support for a
proper mtd device.  it worked... up to a point... except when u-boot
did a complete scan it CORRUPTED the NAND flash... just from reads.

i figured this was "just software" as it's pretty experimental, and
the 3.4.104 sunxi-nand works perfectly.

fast-foward to a few months ago, when i was testing the external
micro-sd slot, weirdly it resulted in a kernel segfault *from the
sunxi-nand driver*.  i thought, "that's weird, might be to do with
current-fighting from the micro-desktop PCB not having level-shifting"

sooo... that's now fixed: the micro-sd slot works perfectly through
the new revision 1.7 microdesktop's level-shifting IC.  however i got
exactly the same kernel segfault in the sunxi-nand driver, so i
temporarily took it out of the kernel config, tested again, and yes,
the micro-sd worked fine.

... except that when i booted it up again, the nand flash had been
corrupted.  now, bear in mind there's *NO DRIVER INSTALLED*.

this is just too weird for me to deal with.  not to mention, because
of the age of the A20's Boot ROM there is now a limited set of
"legacy" NAND ICs available i've had it with them.

now, i _could_ convert to eMMC but it's too much of a major redesign:
it involves disrupting the RGB/TTL tracks, and may require at least
two more rounds of pre-production prototyping...

... it's too much: it's too risky... and i'm getting fed up.  so.
what i'm going to do instead is: cut the NAND IC entirely, then wire
SDC2 (which is the same pins as the NAND) to the *ON-BOARD* Micro-SD
card slot, instead.

what that will give is *two* bootable Micro-SD card options, priority
being first the external one (MMC0) and second the on-board one
(MMC2).

the reason why this will be possible when it was not possible before
was described in another post to the list a couple weeks back: there's
simply no way to route the tracks on such a small 6-layer PCB with the
NAND tracks going from right-to-left, MMC0 has no room to go
left-to-right and at the same time MMC3 going left-to-right.  that's
over 30 tracks trying to cross through space that will only take about
15.

BUT...

... if the NAND tracks are *removed* *NOW* i can route MMC2
(right-hand-side of the A20 pins) to the on-board MicroSD slot (right
of the Card).

i can always do a variant which has eMMC later but right now i
just want to get something out the door as soon as possible with as
little risk as possible.  this approach does have the advantage that
the BoM is about $5 less but it does mean i will need to get
something like...  1,000 MicroSD cards, instead!

l.

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