Re: [PATCH v6 0/8] drm: zynqmp_dp: IRQ cleanups and debugfs support

[Tomi Valkeinen]

Hi,

On 25/10/2024 17:58, Sean Anderson wrote:
> Hi Tomi,
>
> On 10/3/24 10:53, Sean Anderson wrote:
> > On 10/2/24 10:50, Tomi Valkeinen wrote:
> > > Hi,
> > >
> > > On 01/10/2024 21:31, Sean Anderson wrote:
> > > > On 8/9/24 15:35, Sean Anderson wrote:
> > > > > This series cleans up the zyqnmp_dp IRQ and locking situation. Once
> > > > > that's done, it adds debugfs support. The intent is to enable compliance
> > > > > testing or to help debug signal-integrity issues.
> > >
> > > I think the patches 1-7 look fine, and I think I can pick those already to drm-misc if you're ok with that.
> > >
> > > I'm a bit unsure about patch 8, probably mainly because I don't have experience with the compliance testing.
> > >
> > > How have you tested this? With some DP analyzer/tester, I presume?
> >
> > For my test setup I used an oscilloscope hooked up to the displayport
> > output using a fixture that broke the signals out to SMA. Since the
> > oscilloscope cannot emulate a sink, I first had the output connected to
> > a monitor. Then I disabled HPD and reconnected the output to my fixture.
> > This process is described in more detail in the documentation.
> >
> > > I think none of this (patch 8) is needed by almost anybody.
> >
> > Well, I found it very useful for debugging a signal integrity issue I
> > was having. Once I could have a look at the signals it was very clear
> > what the problem was.
> >
> > > Even among zynqmp_dp developers I assume it's very rare to have the
> > > hardware for this. I wonder if it would make sense to have the debugfs
> > > and related code behind a compile option (which would be nice as the
> > > code wouldn't even compiled in), or maybe a module parameter (which
> > > would be nice as then "anyone" can easily enable it for compliance
> > > testing). What do you think?
> >
> > Other drivers with these features just enabled it unconditionally, so I
> > didn't bother with any special config.
> >
> > > I also somehow recall that there was some discussion earlier about
> > > how/if other drivers support compliance testing. But I can't find the
> > > discussion. Do you remember if there was such discussion, and what was
> > > the conclusion? With a quick look, everything in the debugfs looks
> > > generic, not xilinx specific.
> >
> > The last it got discussed was back in [1], but I never got any further
> > response. I agree that some of this is generic, and could probably be
> > reworked into some internal helpers. But I don't have the bandwidth at
> > the moment to do that work.
> >
> > --Sean
> >
> > [1] http://lore.kernel.org/dri-devel/cda22b0c-8d7c-4ce2-9a7c-3b5ab540fa1f@xxxxxxxxx
>
> Does this all make sense to you? At the moment I don't believe I have any
> changes I need to resend for (although this series is archived in patchwork [1]
> for some reason).
>
> --Sean
>
> [1] https://patchwork.kernel.org/project/dri-devel/list/?series=878338&archive=both

I was hoping to get tested-by from amd, as I can't test this properly, 
but it's probably pointless to wait.

The biggest hesitation I have is what I mentioned earlier: this adds a 
lot of code which is not for normal use. It would be nice to split this 
into a separate file, maybe behind a compile option, but I fear that'll 
require a more restructuring of the driver.

So, I think it's fine, I'll apply this tomorrow.

 Tomi