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

[Sam Protsenko]

On Thu, Apr 7, 2016 at 8:07 PM, Steve Rae <steve.rae at broadcom.com> wrote:
> Hi Sam,
>
> On Thu, Apr 7, 2016 at 9:46 AM, Sam Protsenko <semen.protsenko at linaro.org>
> wrote:
>>
>> On Thu, Apr 7, 2016 at 10:36 AM, Lukasz Majewski <l.majewski at samsung.com>
>> wrote:
>> > Hi Steve,
>> >
>> >> 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? )
>> >
>> > I can only speak about DWC2 (from Synopsis) embedded at Samsung boards.
>> > There are low level debugging registers (documented, but not supposed
>> > to be used at normal operation), which give you some impression
>> > regarding very low level events.
>> >
>> > DWC2 at Samsung is using those to work properly since we had some
>> > problems with dwc2 IP blocks implementation on early Samsung
>> > platforms :-). This approach works in u-boot up till now.
>> >
>> > Another option is to use JTAG debugger (like Lauterbach) to inspect
>> > state of this IP block.
>> >
>> >> ( 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?
>> >
>> > As we know the author of this change is not working at Linaro anymore.
>> >
>> >> 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....
>> >
>> > If you don't have enough time (and HW) for investigate the issue, I
>> > think that Kconfig option with documentation entry is the way to go.
>> >
>> > I hope that Sam don't have any objections with such approach.
>> >
>>
>> If this commit doesn't break any platform -- I'm ok with that. If it
>> breaks anything (TI boards particularly) -- I'd ask to revert it at
>> once, as this is I believe not right way to do things.
>
>
> I'm confused...
> You are saying that it is OK to checkin a change that fixes TI boards (Feb
> 25), even though it breaks Broadcom boards;
> but if _this_ change "breaks anything" then it is NOT OK ?????
> ( I politely disagree.... )
> PS - therefore - what is the right way? (..."this is I believe not right way
> to do things"...)
>

Look, it's current state of things. Some stuff is broken, I admit
that. But you can't just break something while fixing another stuff.
It's not even about "your" boards or "my" boards. It's just not right,
I thought it's pretty obvious. So what is correct way to do in that
case? I believe it's fix only boards you know for sure are broken, but
keep old fastboot behaviour for the rest of boards. Not only TI, but
all boards except yours. So that after buildman run you can see that
only your boards were changed, something like that.

>>
>> So Steve, please add
>> CONFIG_USB_GADGET_FASTBOOT_DOWNLOAD_ALIGNMENT_REQUIRED option to all
>> required defconfigs (except yours), so that your patch only fixes your
>> platforms, but doesn't break any other platform at the same time.
>
>
> So -- here is why I cannot complete this task:
> I have absolutely no idea which boards actually _require_ this capability,
> therefore, I have no idea which defconfigs I would need to update!
>

As I see it:

- look into include/configs/*.h
- find all headers that use fastboot capability
- find corresponding TARGET_ for each header
- find all defconfigs for each TARGET_
- your defconfigs should disable alignment
- rest of defconfigs should enable alignment (default behavior)

This way you fix your boards (that you know need to be fixed) but keep
rest of boards intact. If some other boards need to be fixed too --
they will be fixed further by some folks who need that.

> So, if you would send me a list of which defconfig files need to add this
> line, I'll update it....
> OR (I would prefer) you could submit a v3 which includes the boards that you
> know require this capability!
>

I'm not gonna send this patch for you, sorry. I just don't need that,
and I'm not the author of original patch, so it's just not my concern.
I can't even test it for boards that actually broken.

> Let me know,
> Thanks, Steve
>
>>
>>  Also
>> good thing to do after that is check options order in changed
>> defconfigs with "make savedefconfig" rule. Both your current changes
>> and appropriate lines in defconfigs should be committed as a single
>> patch, so that it doesn't break anything and "git bisect" may be used
>> to look for regressions. Also, really nice thing to do after all of
>> this, is to use "./tools/buildman/buildman" tool to check all ARM
>> boards for regressions after your patch (you should see that only your
>> boards were changed).
>
>
> yup -- I use buildman almost exclusively....
>
>>
>> Ideally, we should check it on all boards (or at least on all UDC
>> controllers supported in U-Boot) and figure out what is happening
>> exactly. But I'm totally fine with hack if it fixes real problem on
>> some platforms. I just ask you guys to not break anything else at the
>> same time (although it surely takes much more effort, but still).
>
>
> I'm confused (again) -- why are you asking: "you guys to not break anything
> else"...
> IT IS ALREADY BROKEN, it is broken right now, and has been broken since Feb
> 25 !
>
> Please fix this!
>

...So let's fix half of platforms and break the other half of
platforms altogether? It's not for me to decide, I'm not the
maintainer. But it just doesn't feel right to me.

I understand your concern, and I can help you test your patches on my
boards any time and also run some debug patches to see the difference.
But I can't fix it for you. Also I'm not sure that your patch would be
merged in current shape (it's basically a hack). So if I were you I'd
try to figure out the root cause of this issue by comparing results of
some debug patches and tests, by running them on your boards (where
fastboot is broken) and on some boards where fastboot is working.
Maybe running wireshark in both cases can help to understand why it's
happening. From my POV it was a good assumption (made by someone
earlier) that possible reason is different UDC controllers (I have
DWC3 on my TI boards).

>>
>> >> 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
>> >>
>> >
>> >
>> >
>> > --
>> > Best regards,
>> >
>> > Lukasz Majewski
>> >
>> > Samsung R&D Institute Poland (SRPOL) | Linux Platform Group
>
>