[Bug 172421] New: radeon: allow to set the TMDS frequency by a special kernel parameter

[Bug 172421] New: radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

            Bug ID: 172421
           Summary: radeon: allow to set the TMDS frequency by a special
                    kernel parameter
           Product: Drivers
           Version: 2.5
    Kernel Version: 4.8.0-rc7+
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: estellnb@elstel.org
        Regression: No

Despite different claims by ATI in 2016 Radeon R5 230 graphics cards featuring
HDMI, DVI and VGA had originally been sold as 4K-ready up to the year 2015. The
only prove I have for this is a comercial invoice from Nexus Mobile and a
packaging card. As far as I know Radeon R5 230 cards currently sold can still
be run stable and reliable under UltraHD provided that you apply the right
kernel patch (see for the attachement). Unfortunately neither my former
merchant nor ATI have responded about my questions concerning this change in
trade and marketing policy.

  My request would now be to integrate the provided patch into the mainline
kernel. It does not change the behaviour of the radeon driver unless you
specify a nonzero value for the radeon.hdmimhz parameter. If you do I have
tested the R5 230 cards I have to run stable and reliably for days. At least
the 2GB variant of this card has largely sufficient resources for proficient
desktop computing under UltraHD including image manipulation in 3840x2160.

  While never officially discussed for the radeon driver nouveau is already
implementing a similar parameter called nouveau.hdmimhz since kernel 4.5.x.
Though it thereby becomes possible to specify a hdmimhz that is far above the
cards technical possibilties the nouveau developers I have talked with say that
it would rarely be possible to damage any card by overcloking the TMDS. In deed
I have successfully been overclocking my GeForce 9600M GT to feature 4K/2160p. 

  Even specifying values considerable higher than 225MHz did not damage my
GeForce 9600M GT though the screen stayed black upon the nouveau driver
initialization. While the Radeon R5 230 works well at 297MHz (as long as you
specify that via radeon.hdmimhz) I have similarly to the GeForce 9600M GT tried
to overclock a Radeon R7 240. It did produce stable images at a higher hdmimhz
like 330 though the HDMI input of my monitor features no more than 30Hz at
3840x2160 (tested with or without a DP-adapter).

  While it remains questionable if the provided patch can improve things for
newer Radeon cards I would believe it to be beneficial for some elder cards. At
least it is known to be beneficial for the R5 230 initially marketed as
4K-ready. The according radeon patch provided with this report has so far
already been accepted by the Mageia 6 distribution. Though the attached patch
is for application at the current 4.8.0-rcX+ kernels most of my machines that
rely on it still run with 4.6.0.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #1 from Elmar Stellnberger <estellnb@elstel.org> ---
Created attachment 239371
  --> https://bugzilla.kernel.org/attachment.cgi?id=239371&action=edit
shipment notification: R5 230 marketed as 4K-ready

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #2 from Elmar Stellnberger <estellnb@elstel.org> ---
Created attachment 239381
  --> https://bugzilla.kernel.org/attachment.cgi?id=239381&action=edit
patch introducing radeon.hdmimhz for kernel 4.8.0-rc2

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

Alex Deucher <alexdeucher@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alexdeucher@gmail.com

--- Comment #3 from Alex Deucher <alexdeucher@gmail.com> ---
NACK.  I rejected this the last time you brought this up.  You are running the
hw outside of it's validated specs.  See this discussion:
https://bugs.freedesktop.org/show_bug.cgi?id=93885

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #4 from Elmar Stellnberger <estellnb@elstel.org> ---
  It is not true that this card would only feature a TMDS of 297 over DP. The
card I have bought does only have HDMI, DVI and 4K and it was sold as 4K-ready
as you can see from the first attachement.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #5 from Elmar Stellnberger <estellnb@elstel.org> ---
... and VGA

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #6 from Alex Deucher <alexdeucher@gmail.com> ---
The asic supports 4K over DP or duallink DVI.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #7 from Elmar Stellnberger <estellnb@elstel.org> ---
  It obviously works stable over HDMI as well. Besides this I have just tested
an ATI Mobility Radeon HD 2600 XT/2700 and it can provide 3840x2160_22.00 over
its HDMI port with a radeon.hdmimhz of 250. With a hdmimhz of 297 I get some
screen distortions but that does not harm the card.
  Why not just unlock a new feature of so many radeon cards? Nouveau developers
did so for long with their device driver.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #8 from Alex Deucher <alexdeucher@gmail.com> ---
Running the hardware out of spec is not something we want to support.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #9 from Elmar Stellnberger <estellnb@elstel.org> ---
any other opinion by someone else on this issue?

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

Christian König <deathsimple@vodafone.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |deathsimple@vodafone.de

--- Comment #10 from Christian König <deathsimple@vodafone.de> ---
Driving the PLL and transmitter way over it's limit is clearly not a good idea
and can potentially cause hardware failure in the long term.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #11 from Elmar Stellnberger <estellnb@elstel.org> ---
  For the R5 230 long time experience is already available. I am successfully
using this card at least since February 2016 at a TMDS of 297Mhz and these
cards are doing very well on basis of everyday use as well as occasional full
throttle.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #12 from Elmar Stellnberger <estellnb@elstel.org> ---
  Today I approached to try out the dual-link feature of the DVI-port. First I
had verified with AOC that my u2868pqu monitor in deed supports dual-link over
DVI. Then I connected the DVI output of my R5 230 (comment #6) with the
u2868pqu monitor over DVI. Trying to boot with a vanilla/hdmimhz=0 I just ended
up with a black screen. Finally I did succeed to get a picture by setting
hdmimhz=165. Firstly amazed I then noticed that hdmimhz does also disable the
duallink feature which was obviously the cause why it worked with hdmimhz. My
explanation for this is that the radeon driver detected both the display and
the card to support dual-link DVI. However the cable does not.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

Roland Scheidegger <rscheidegger@gmx.ch> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rscheidegger@gmx.ch

--- Comment #13 from Roland Scheidegger <rscheidegger@gmx.ch> ---
(In reply to Elmar Stellnberger from comment #9)
> any other opinion by someone else on this issue?

FWIW enthusiasts love such things, but corporations do not. Hence you don't see
overclocking and similar unspecified stuff in drivers not maintained by
community generally.
Personally I've always thought the risk of damaging hardware with any kind of
overclocking is just about exactly zero as long as you don't increase voltage
levels (and you can handle the additional heat but that should be a non-issue
here). That's my limited understanding of the physics behind it :-).
I suspect part of the reason why it overclocks so well is also that this chip
should be DP 1.2 capable - meaning HBR2 mode which has a clock of 270Mhz (not
that you can really get cards with that chip which actually do have the DP
port...). Now the signalling is different with DP vs. HDMI/DVI but if I had to
take a guess I'd suspect the hw is mostly all the same.
But none of that is going to change the opinion of overclocking of anyone...

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #14 from Christian König <deathsimple@vodafone.de> ---
(In reply to Roland Scheidegger from comment #13)
> Personally I've always thought the risk of damaging hardware with any kind
> of overclocking is just about exactly zero as long as you don't increase
> voltage levels

Unfortunately this is exactly what happens here. The clock is generated by a
voltage controlled oscillator and for the desired resolution you need to over
clock it by about 30-40%.

That in turn means you raise the voltage way over the nominal limit.

Those oscillators are designed to handle voltages about 250% over the nominal
level without frying immediately, but that says absolutely nothing about the
aging of the circuit under those conditions.

The PLL we are talking about here clearly isn't designed for that level of
operation and even the closed source driver (which are otherwise rather
friendly to overclocking) don't let the user override this absolute limit.

So this is a clearly NAK from my side.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #15 from Roland Scheidegger <rscheidegger@gmx.ch> ---
(In reply to Christian König from comment #14)
> (In reply to Roland Scheidegger from comment #13)
> > Personally I've always thought the risk of damaging hardware with any kind
> > of overclocking is just about exactly zero as long as you don't increase
> > voltage levels
> 
> Unfortunately this is exactly what happens here. The clock is generated by a
> voltage controlled oscillator and for the desired resolution you need to
> over clock it by about 30-40%.
> 
> That in turn means you raise the voltage way over the nominal limit.

Oh interesting - didn't know voltage was directly tied to clock frequency here.
Makes sense then to not allow it (at least if that circuitry isn't shared with
DP, as the DP link runs at much higher clock (540Mhz actually), but I suppose
it's really different there).

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #16 from Christian König <deathsimple@vodafone.de> ---
(In reply to Roland Scheidegger from comment #15)
> Oh interesting - didn't know voltage was directly tied to clock frequency
> here. Makes sense then to not allow it (at least if that circuitry isn't
> shared with DP, as the DP link runs at much higher clock (540Mhz actually),
> but I suppose it's really different there).

The voltage is only indirectly related, but yes over clocking such parts is a
rather bad idea in the long term.

DP uses a fixed frequency which is way easier to generate than the variable
HDMI/DVI/VGA clock.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #17 from Elmar Stellnberger <estellnb@elstel.org> ---
  The patch does not only allow overclocking; it can also be used to disable
the duallink feature. In certain cases this may be necessary to get a picture
at all (see comment 12).

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

Paweł Zmarzły (pawo2500@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pawo2500@gmail.com

--- Comment #18 from Paweł Zmarzły (pawo2500@gmail.com) ---
I've just tried this patch on Radeon HD 6850 and it works great (2560x1080 at
185.58Mhz). While indeed it's more than AMD site says is supported, official
AMD drivers for Windows support this resolution out-of-the-box, so I think it's
safe to at least increase the limit to 186 Mhz.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

John (sirfixabyte@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sirfixabyte@gmail.com

--- Comment #19 from John (sirfixabyte@gmail.com) ---
I read all the previous comments - for and against the adoption of the patch. 
Question: Why is it easy to find a pixel clock patch for WINDOWS
(www.monitortests.com AMD/ATI Pixel Clock Patcher by someone named 'ToastyX')
-available and supported since 2012 - and successfully running 4K screens
(since January 2016) on the same Radeon cards being discussed here ? Many
people on that webpage discussing it. Seems to work. I personally tested on a
few older Radeon cards and it works at 3840x2160 for me.  I have NOT yet run it
for hours (I rarely run Windows, and then only to test of fix PC's for others).
I have not connected temperature sensors to heat sinks yet.

If the pixel clock generator circuitry is on the same die as everything else,
then it shares a heat sink.  The whole thing designed such that with
recommended airflow across that heat sink, the GPU remains functional. BUT,
that can mean running 3 separate displays - utilizing the full capacity of the
GPU. 

IF this patch from Elmar Stellnberger were to be used to run a SINGLE 4K LCD at
3840 x 2160 at 30% overclock on the pixel clock generator, maybe the overall
GPU would be generating much less than maximum heat, and the heatsink/fan could
easily keep it cool.

Does anyone have a maximum pixel clock specification for the various pixel
clock generator designs on the various ATI/AMD dies ? 
Did ATI set limits due to HDMI cables and overall ability of heatsink to
dissipate the heat when running the GPU at max speed / load on 3 screens ?
Is there a listed maximum voltage that the PLL can run at - long term - without
damage ? for most integrated circuits data sheets I have ever read, there is a
relationship between max speed and temperature of the die.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #20 from John (sirfixabyte@gmail.com) ---
also, the patch allowing pixel clock increase for Nvidia cards has been in
kernel since 4.5.n - also something I successfully tested recently at 3840x2160
resolution on OLD Nvidia card.  I thought Linux was the OS that is supposed to
allow experiments and variety & versatility. Seems like NOT if talking Radeon
cards.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=172421

Joachim Hoss (joachim.hoss@koeln.de) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |joachim.hoss@koeln.de

--- Comment #21 from Joachim Hoss (joachim.hoss@koeln.de) ---
Wiht the help of Elmar Stellenberger's patch to kernel 4.20 I can now run my
old Radeon HD 5870 at 3840x1600 resolution, which it does "out of the box"
under widows. 
I would also like to recommend this patch for inclusion in the kernel.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

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https://bugzilla.kernel.org/show_bug.cgi?id=172421

--- Comment #22 from Elmar Stellnberger (estellnb@elstel.org) ---
  The patch was not accepted because someone claimed it could damage the
hardware. All lies. As years have gone by these graphics cards are still under
daily use with this UHD patch and no damages have ever occured. As this
hardware is still in use I would really like to see this in mainline, not just
the Mageia kernel. Someone who knows about it, told it would be highly
improbable that this could be detrimental for the hardware. The only fallacy
would be that the screen shows black on a too high TMDS and nobody would ever
continue to run the graphics card with a TMDS that yields a black screen. This
hardware is near to getting phased out on many computers by now and I´d regard
it as ridiculous if the patch is withheld because of the argument that it could
damage hardware on the long run. This hardware will get phased out long before
any damage could ever occur.
  As distributors and kernel developers still support Pentium IV hardware I am
reopening this bug. This is about Core 2 aged hardware which is totally
sufficient for UHD/desktop computers. I would never give up my Xi3650 machines
because they are ultimately silent, something you don´t get with a newer
computer. And unfortunately the Xi3650 does not work with newer 3D gaming UHD
graphics cards (these cards inhibt s2ram also on Windows, which isn´t what you
want for a desktop system)

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Matt Weiland (matt.weiland@gmx.at) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matt.weiland@gmx.at

--- Comment #23 from Matt Weiland (matt.weiland@gmx.at) ---
I think it a rather political issue that the patch has not been accepted up to
now. So many people have reported about it being useful not only on the kernel
bugzilla here and I would really welcome it if you kernel developers started to
rethink your decision about it. There is still time and the patch is still
being useful.

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[Bug 172421] radeon: allow to set the TMDS frequency by a special kernel parameter

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Eduard Bloch (blade@debian.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |blade@debian.org

--- Comment #24 from Eduard Bloch (blade@debian.org) ---
Hey guys, I am trying to port this mod to AMDGPU. The intention is, however,
not to unlock the advertised features but to force an APU to accept HDMI clocks
over a DVI port (with DVI-HDMI cable, the monitor expects HDMI signal).

The port itself is easy but it does not work. amdgpu.hdmimhz=... parameter has
apparently no effect, Xorg keeps reporting:

[    16.107] (--) AMDGPU(0): HDMI max TMDS frequency 280000KHz

Does anyone have an idea how to tackle this?

Here is the patch:
https://github.com/Code7R/linux/commits/amdgpu-custom-maxtdmsclock

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James Hendry (jameshendry05@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jameshendry05@gmail.com

--- Comment #25 from James Hendry (jameshendry05@gmail.com) ---
With the help of Elmar Stellenberger's patch to the kernel, I managed to make a
patch to the 6.2.0 kernel that allowed me to use a DisplayPort -> HDMI adaptor
for my ultrawide monitor (2560x1080@60Hz). the 165Mhz was just below what i
required (I needed about 166Mhz for my monitor) so very very minimal
over-clocking to go from not working at all to working perfectly. This worked
natively in windows so clearly they have determined that it is acceptable, so I
don't see any real risk.

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