On Wednesday 25 May 2016 10:25:29, Meng Yi wrote:
> Hi Alexander,
> Thanks for your reply.
>
> > Commit d761701c55a99598477f3cb25c03d939a7711e74 only has one child
> > commit in my repo. Both touch only i915 related things. Please do a proper
> > bisect and name the offending commit. On which commit you got that
> > backtrace BTW?
> > From your backtrace I can't see anything related to regmap.
>
> It is weird that using bisect, for the commit log is not linear.
> I mean a newer date commit may be merged before an older date commit, when
> jump to that older date commit, the newer one will be lost, even though it
> is merged before older one. So, I think it's difficult to use git bisect.
> " d761701c55a99598477f3cb25c03d939a7711e74 " is just an older one, I mean
> between this commit and the next commit, maybe lots of commits are lost.
> So, it looks like this commit have nothing to do with the problem.
Why are commits lost? The order of commit dates is not straightforward, yes,
but that's not a problem at all.
> According to the backtrace, looks like the vblank interrupt is not happen or
> handled. Then I found the irq is installed successfully, so the problem
> seems like the vblank irq is not properly setup. And here is the point ,
> irq initia, irq handler and timing control code are using regmap.
>From your backtrace I guess wait_event_timeout is called in some atomic
context (might_sleep(); is called inside wait_event_timeout). This has nothing
to do with regmap.
> I read out the value of relevant register using "CodeWarrior TAP", find that
> endianness is not right.
>
> Then I changed endianness of the value to be written that using "
> regmap_write" . It works. But "regmap_update_bits" still have the problem.
>
> I had checked log of regmap, and didn't find which commit caused that.
The inital problem came up with 922a9f936e40001f9b921379aab90047d5990923
("regmap: mmio: Convert to regmap_bus and fix accessor usage"). The commits
9f9f8b863ad130ec0c25f378bdbad64ba71291de,
4f7d6dd4df8b388e2056c89b528254cdd79dea2a and
0dbdb76c0ca8e7caf27c9a210f64c4359e2974a4 tried to fix that. With those I could
successfully probe DCU.
Best regards,
Alexander
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