[U-Boot] [PATCH v2] fastboot: OUT transaction length must be aligned to wMaxPacketSize

[Steve Rae]

No -- I do not believe that this issue is caused by different fastboot
(client) versions (the executable that runs on the host computer -
Linux, Windows, Mac, etc.)
I have personally attempted three (3) different versions, and the
results are consistent.

And no I don't think that I "am the only hope at fixing this proper"
-- as you will see below,
this" issue" seems to be unique to the "TI platforms" (... nobody else
has stated they have an issue either way -- but I don't think many use
this feature ....)
So maybe someone with "TI platforms" could investigate this more thoroughly...

HISTORY:

The U-Boot code, up to Feb 25, worked properly on my Broadcom boards
-- this code contains:
               req->length = rx_bytes_expected();
                if (req->length < ep->maxpacket)
                        req->length = ep->maxpacket;
which aligned the remaining "rx_bytes_expected" to be aligned to the
"ep->maxpacket" size.

On Feb 25, there was a patch applied from <dileep.katta at linaro.org>
which forces the remaining "rx_bytes_expected" to be aligned to the
"wMaxPacketSize" size -- this patch broke all Broadcom boards:
+       if (rx_remain < maxpacket) {
+               rx_remain = maxpacket;
+       } else if (rx_remain % maxpacket != 0) {
+               rem = rx_remain % maxpacket;
+               rx_remain = rx_remain + (maxpacket - rem);
+       }

After attempting to unsuccessfully contact Dileep, I requested that
this patch be reverted -- because it broke my boards! (see the other
email thread).

Sam Protsenko <semen.protsenko at linaro.org> has stated that this Feb 25
change is required to make "fastboot work on TI platforms".

Thus,
- Broadcom boards require alignment to "ep->maxpacket" size
- TI platforms require alignment to "wMaxPacketSize" size
And we seem to be at a stale-mate.
Unfortunately, I do not know enough about the USB internals to
understand why this change breaks the Broadcom boards; or why it _is_
required on the TI platforms....
( Is there any debugging that can be turned on to validate what is
happening at the lower levels? )
( Can anyone explain why "wMaxPacketSize" size would be required? --
my limited understanding of endpoints makes me think that
"ep->maxpacket" size is actually the correct value! )

I asked Sam to submit a patch which conditionally applied the
alignment to "wMaxPacketSize" size change -- he stated that he was too
busy right now -- so I submitted this patch on his behalf (although he
still needs to add the Kconfig for the TI platforms in order to make
his boards work)....

I suppose I could also propose a patch where the condition _removes_
this feature (and define it on the Broadcom boards)  -- do we
generally like "negated" conditionals?
+#ifndef CONFIG_USB_GADGET_FASTBOOT_DOWNLOAD_DISABLE_ALIGNMENT_WITH_WMAXPACKETSIZE
Please advise!

Further, how does the U-Boot community respond to a change which
breaks something which is already working? Doesn't the "author" of
that change bear any responsibility on assisting to get "their" change
working properly with "all" the existing boards? I'm getting the
impression that "because the current code works for me", that I am not
getting any assistance in resolving this issue -- which is why I
suggested "reverting" this change back to the original code; that way,
it would (politely?) force someone interested in "TI platforms" to
step up and look into this....

Sorry for asking so many questions in one email -- but I'd appreciate
answers....
( I also apologize in advance for the "attitude" which is leaking into
this email... )
Please tell me what I can do! I had working boards; now they are all
broken -- and I don't how how to get them working again....
Thanks, Steve

On Wed, Apr 6, 2016 at 4:01 AM, Marek Vasut <marex at denx.de> wrote:
> On 04/06/2016 07:35 AM, Steve Rae wrote:
>>
>> On Apr 5, 2016 3:07 PM, "Marek Vasut" <marex at denx.de
>> <mailto:marex at denx.de>> wrote:
>>>
>>> On 04/05/2016 08:31 PM, Steve Rae wrote:
>>> > commit 9e4b510 fastboot: OUT transaction length must be aligned to
>> wMaxPacketSize
>>> > breaks some boards...
>>> >
>>> > Therefore add a conditional Kconfig to optionally enable this feature.
>>>
>>> Did you drill into it to figure out why this is needed ?
>>>
>>
>> Marek,
>> Let me clarify....
>> All my boards work with the original code (before the commit which
>> aligned  the size to the wMaxPacketSize).... Since that commit, all my
>> boards are broken.
>> And you will notice in this patch, that none of my boards define this
>> CONFIG_ ...
>>
>> So I think you are asking the wrong person to drill down into this issue....
>> Sorry, Steve
>
> Well who else can I ask ? You're our only hope at fixing this proper.
>
> Anyway, see my other reply, maybe we should just add an arg to fastboot
> command to select one more of operation or the other and default to the
> one which works.
>
> --
> Best regards,
> Marek Vasut