[Bug 200045] New: i2c-algo-bit: black screen on 'radeon' module probing

[Bug 200045] New: i2c-algo-bit: black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

            Bug ID: 200045
           Summary: i2c-algo-bit: black screen on 'radeon' module probing
           Product: Drivers
           Version: 2.5
    Kernel Version: 4.16
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: cerg2010cerg2010@mail.ru
        Regression: No

Created attachment 276499
  --> https://bugzilla.kernel.org/attachment.cgi?id=276499&action=edit
lspci -v

Hi,

After updating to the 4.16 kernel I started to get a black screen on boot,
without something useful in log. This bug also happens in latest version
(4.17.1). I'm using HP Pavilion dv6-3090er laptop with an exotic ATI/AMD
switchable graphics (radeon 4250 integrated/5650 discrete).

I bisected the issue down to commit 3e5f06bed72fe72166a6778f630241a893f67799
("i2c: algo-bit: init the bus to a known state") and reverting this fixes the
problem. Also loading radeon module with hw_i2c=1 gives me working display with
full brightness, and attempt to change it results in reboot.

Thanks.

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

cerg2010cerg2010@mail.ru changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|i2c-algo-bit: black screen  |black screen on 'radeon'
                   |on 'radeon' module probing  |module probing

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #1 from cerg2010cerg2010@mail.ru ---
Ok, actually this is 4.17 issue; on 4.16 hw_i2c=1 fixes the issue completely,
but on 4.17 changing backlight in Xorg (using keys) causes a reboot, fbcon
works fine though.

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #2 from Wolfram Sang (wsa@the-dreams.de) ---
Okay, these are actually two bug reports meanwhile:

1) 3e5f06bed72fe72166a6778f630241a893f67799 causes a regression when
bit-banging I2C in software and results in keeping the screen black.

2) There is some regression when using the a HW interface for I2C which causes
a reboot when changing the brightness.

I'd suggest to work only on 1) here and create a new bug report for 2). I
should be able to give you some patches to test in a few minutes.

Thanks for the report and the bisecting!

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #3 from cerg2010cerg2010@mail.ru ---
I did some more research and it turns out that 2) happens if I change
brightness level right after X starts, even in 4.15 kernel. If I wait a bit,
everything works good, including 4.17.1. Software I2C doesn't reproduce same
results, so I'm not sure if I should report 2) because it's stated that it can
cause issues, but with different kind of errors:

[drm] hw_i2c forced on, you may experience display detection problems!

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #4 from Alex Deucher (alexdeucher@gmail.com) ---
hw_i2c doesn't use bit banging, it uses the hw i2c engine.

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #5 from Wolfram Sang (wsa@the-dreams.de) ---
Sure. But reading the original description above, I think the default use case
is to not use hw_i2c. It was just added to try to work around the regression.
And that led to another bug. Or am I wrong here?

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #6 from Wolfram Sang (wsa@the-dreams.de) ---
So, I really posted the patches now. Sorry, I got side-tracked.

They can be found here:

http://patchwork.ozlabs.org/patch/929185/
http://patchwork.ozlabs.org/patch/929186/

I set you on CC as well. As indicated in the cover letter, could you try these
patches one by one?

Thanks and kind regards.

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #7 from Alex Deucher (alexdeucher@gmail.com) ---
(In reply to Wolfram Sang from comment #5)
> Sure. But reading the original description above, I think the default use
> case is to not use hw_i2c. It was just added to try to work around the
> regression. And that led to another bug. Or am I wrong here?

Correct.  I was just clarifying that that option does.

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #8 from cerg2010cerg2010@mail.ru ---
Ok, I tested the patches, but they did not fix the problem. Nothing changed,
and the log is empty. I tried to apply them separately and both at the same
time. Note that second one seems to depend on the first, so I had to apply it
manually.

Thanks for trying to fix the issue!

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #9 from Wolfram Sang (wsa@the-dreams.de) ---
Created attachment 276551
  --> https://bugzilla.kernel.org/attachment.cgi?id=276551&action=edit
print initial states to allow further debug

Thanks for testing the patches, pity it didn't help.

Would you mind testing with the attached patch? It should give some output
about the initial states. Let's hope that will lead to something...

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #10 from cerg2010cerg2010@mail.ru ---
Here is the output:

[   23.056329]  (null): initial SCL state 1
[   23.056330]  (null): initial SDA state 1
[   23.056532]  (null): initial SCL state 1
[   23.056534]  (null): initial SDA state 1
[   23.056578]  (null): initial SCL state 0
[   23.056580]  (null): initial SDA state 0
[   23.056617]  (null): initial SCL state 0
[   23.056618]  (null): initial SDA state 0
[   23.056656]  (null): initial SCL state 0
[   23.056657]  (null): initial SDA state 0

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #11 from Wolfram Sang (wsa@the-dreams.de) ---
I have sent another patch, let's hope it really is this issue:

http://patchwork.ozlabs.org/patch/929798/

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #12 from cerg2010cerg2010@mail.ru ---
Teset this, but it did not help.

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

Wolfram Sang (wsa@the-dreams.de) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #276551|0                           |1
        is obsolete|                            |

--- Comment #13 from Wolfram Sang (wsa@the-dreams.de) ---
Created attachment 276571
  --> https://bugzilla.kernel.org/attachment.cgi?id=276571&action=edit
WIP to test

Pity that it didn't work. The thing is that I am quite sure the pre/post_xfer
calls are needed. I am running out of ideas now.

The best thing I can come up with is this patch which adds all the stuff
altogether. I don't have high hopes, but maybe all 3 improvements make it work.
At least, the debug output will be better, it was a bit meaningless before.

If this still doesn't work, could you move the new code block from this patch
after the add_adapter() call and try again (with the old block still deleted)?

Thanks for all the testing!

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[Bug 200045] black screen on 'radeon' module probing

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #14 from cerg2010cerg2010@mail.ru ---
Still nothing changed... This is what I got in both cases:

[   57.656675] Radeon i2c bit bus 0x90: initial SCL state 1
[   57.656678] Radeon i2c bit bus 0x90: initial SDA state 1
[   57.656805] Radeon i2c bit bus 0x91: initial SCL state 1
[   57.656807] Radeon i2c bit bus 0x91: initial SDA state 1
[   57.656921] Radeon i2c bit bus 0x92: initial SCL state 0
[   57.656924] Radeon i2c bit bus 0x92: initial SDA state 1
[   57.660108] Radeon i2c bit bus 0x93: initial SCL state 0
[   57.660111] Radeon i2c bit bus 0x93: initial SDA state 0
[   57.664128] Radeon i2c bit bus 0x14: initial SCL state 0
[   57.664131] Radeon i2c bit bus 0x14: initial SDA state 0

And if I leave only printing code (i.e get the working state):

[   23.992763] Radeon i2c bit bus 0x90: initial SCL state 1
[   23.992766] Radeon i2c bit bus 0x90: initial SDA state 1
[   23.992851] Radeon i2c bit bus 0x91: initial SCL state 1
[   23.992854] Radeon i2c bit bus 0x91: initial SDA state 1
[   23.992938] Radeon i2c bit bus 0x92: initial SCL state 0
[   23.992941] Radeon i2c bit bus 0x92: initial SDA state 0
[   23.993080] Radeon i2c bit bus 0x93: initial SCL state 0
[   23.993082] Radeon i2c bit bus 0x93: initial SDA state 0
[   23.993146] Radeon i2c bit bus 0x14: initial SCL state 0
[   23.993148] Radeon i2c bit bus 0x14: initial SDA state 0

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #15 from Wolfram Sang (wsa@the-dreams.de) ---
I will just revert this commit. I have no further ideas for remote debugging. I
think reverting is the safest solution for now, I can't find any patches since
v4.16 which added users to this bitbanging algorithm. So, there can't be anyone
depending on the new functionality. And I will try to fix my original issue one
layer above at the i2c-gpio level.

Thanks for reporting! Would you reveal your real name for a proper
"Reported-by:" tag?

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[Bug 200045] black screen on 'radeon' module probing

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https://bugzilla.kernel.org/show_bug.cgi?id=200045

--- Comment #16 from Sergey Larin (cerg2010cerg2010@mail.ru) ---
My name is Sergey Larin, I added it to my account. Thanks for your help!

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