[yocto] (IIO) ADC freeze on am335x processor on 3.14.26ltsi kernel

[Yani Dubin]

Hi Bruce,

On 28 January 2015 at 04:08, Bruce Ashfield <bruce.ashfield at windriver.com>
wrote:

>  On 15-01-26 11:54 PM, Yani Dubin wrote:
>
> These are 3 adjacent changesets on the dizzy branch - I gather that is as
> much as I can narrow it down?
>
>  We may need to get your help in tracking the problem down, since without
> the h/w on hand, it will be difficult to figure out what changed between
> the
> working and non-working revisions.
>
> I have some additional 3.14 updates queued, and they may fix the issue ..
> but again, I can't say for sure.
>
> Are you able to bisect the kernel directly ? I only submit SRCREV updates
> to
> the linux-yocto recipes at particular milestones, but within the kernel we
> obviously have more granularity.
>
> After you've built the kernel the first time, you can head into devshell
> and
> then use the unpacked and patched src tree and do a normal git bisect/build
> workflow. You'd need to copy the resulting kernels out to your target, but
> that
> would narrow down the bad commit/merge pretty quickly.
>

Bisecting the 1800+ changesets between these points yielded a culprit:
[bb01842184bc89666819ee7dceb78c61505036ed] mfd: ti_am335x_tscadc: Fix TSC
operation after ADC continouous mode

This is a two line changeset. I have confirmed that reverting the second
change against the previously broken version fixes it for me. So I now have
a patch I can apply locally until such time as this is fixed upstream.

Since this is my first time reporting a kernel bug, and I now know exactly
what I am looking for can you give me any pointers on where/how to search
to see if an upstream fix exists already?

Thank you for your help, and a welcome introduction to both devshell (I
used to do kernel reconfigure/compile the hard way) and git bisect - I can
see these are going to be very handy in the future.

Thanks again,
Yani.

-- 

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