Re: [PATCH v8 07/14] ARM: dts: rockchip: add clocks in iommu nodes

Heiko Stuebner
2018-04-10T10:54:17Z

Am Montag, 9. April 2018, 23:49:58 CEST schrieb Heiko Stübner:
> Am Montag, 9. April 2018, 17:55:40 CEST schrieb Heiko Stübner:
> > Am Montag, 9. April 2018, 17:53:01 CEST schrieb Robin Murphy:
> > > On 09/04/18 16:44, Heiko Stübner wrote:
> > > > Hi Tomeu,
> > > >
> > > > Am Montag, 9. April 2018, 16:41:56 CEST schrieb Tomeu Vizoso:
> > > >> in today's linux-next, the DRM driver fails to probe because the iommu
> > > >> driver fails to find the aclk. I need to apply this patch for things
> > > >> to work again.
> > > >
> > > > Thanks for catching that issue.
> > > >
> > > > This seems to expose a backwards-compatibility issue, as this breaks
> > > > all old devicetrees, so should get a proper fix, apart from me applying
> > > > the dt-patch I missed.
> > > >
> > > > Looking at the iommu-clock-handling patch, I imagine this part as
> > > > the culprit:
> > > >
> > > > + iommu->num_clocks = ARRAY_SIZE(rk_iommu_clocks);
> > > > + iommu->clocks = devm_kcalloc(iommu->dev, iommu->num_clocks,
> > > > + sizeof(*iommu->clocks), GFP_KERNEL);
> > > > + if (!iommu->clocks)
> > > > + return -ENOMEM;
> > > >
> > > > The clk-bulk functions seem to work with simple for loops and
> > > > should (as the other standard clock functions) just work fine with
> > > > an empty struct, so I guess a simple
> > > >
> > > > if (!iommu->clocks && iommu->num_clocks > 0)
> > > >
> > > > return -ENOMEM;
> > > >
> > > > should hopefully be enough. I'll try to give this a test later on
> > > > if nobody beats me to it :-)
> > >
> > > But iommu->num_clocks is clearly set to a nonzero compile-time constant
> > > at this point ;)
> > >
> > > I'd assume it's the return from devm_clk_bulk_get() which needs to
> > > special-case the "no clocks found" case from any other error, and *then*
> > > blat num_clocks to 0 if so.
> >
> > you're right of course. Looking at it again, I now clearly see the
> > ARRAY_SIZE and am wondering what made me think num_clocks would be
> > runtime-read.
> >
> > Must be those 25°C today ;-)
>
> In any case, this does not seem to fully fix the issue ... or be more exact
> seems to be the only issue.
>
> - With 4.16 both pinky and kevin have working displays.
> - When I was merging display patches to drm-misc, I did boot-tests on
> both pinky and kevin, keeping their displays in a working state.
>
> - With current torvalds head (iommu not merged yet)
> e9092d0d9796 ("Fix subtle macro variable shadowing in min_not_zero()")
>
> I get display output on rk3399-kevin (edp), but not on
> rk3288-pinky (edp + hdmi). [components + hdmi device+modes get
> recognized correctly though]
>
> - With iommu changes merged I end up with the failing clock issue
> which can be countered by making the iommu-clocks optional.
>
> - After that I get working display output again on kevin but not pinky.
>
> Looks like this needs bisecting.

And it seems the dwc2 vbus thingy was responsible for the other issue I saw.
With Tomeus fixup patch applied and the series I sent an hour ago, I now
get display output again on both kevin (rk3399) and pinky (rk3288).

Heiko