Hi Peter, On Thursday 19 Jan 2017 10:25:32 Peter Senna Tschudin wrote: > On Thu, Jan 19, 2017 at 10:17:45AM +0200, Laurent Pinchart wrote: > > On Thursday 19 Jan 2017 09:12:14 Peter Senna Tschudin wrote: > >> On Wed, Jan 18, 2017 at 11:10:58PM +0200, Laurent Pinchart wrote: > >>> On Monday 16 Jan 2017 09:37:11 Peter Senna Tschudin wrote: > >>>> On Tue, Jan 10, 2017 at 11:04:58PM +0200, Laurent Pinchart wrote: > >>>>> On Saturday 07 Jan 2017 01:29:52 Peter Senna Tschudin wrote: > >>>>>> On 04 January, 2017 21:39 CET, Rob Herring wrote: > >>>>>>> On Tue, Jan 3, 2017 at 5:34 PM, Peter Senna Tschudin wrote: > >>>>>>>> On 03 January, 2017 23:51 CET, Rob Herring <robh@xxxxxxxxxx> wrote: > >>>>>>>>> On Sun, Jan 01, 2017 at 09:24:29PM +0100, Peter Senna Tschudin > > wrote: > >>>>>>>>>> Devicetree bindings documentation for the GE B850v3 LVDS/DP++ > >>>>>>>>>> display bridge. > >>>>>>>>>> > >>>>>>>>>> Cc: Martyn Welch <martyn.welch@xxxxxxxxxxxxxxx> > >>>>>>>>>> Cc: Martin Donnelly <martin.donnelly@xxxxxx> > >>>>>>>>>> Cc: Javier Martinez Canillas <javier@xxxxxxxxxxxx> > >>>>>>>>>> Cc: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx> > >>>>>>>>>> Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > >>>>>>>>>> Cc: Rob Herring <robh@xxxxxxxxxx> > >>>>>>>>>> Cc: Fabio Estevam <fabio.estevam@xxxxxxx> > >>>>>>>>>> Signed-off-by: Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx> > >>>>>>>>> --- > >>>>>>>>>> There was an Acked-by from Rob Herring <robh@xxxxxxxxxx> for > >>>>>>>>>> V6, but I changed the bindings to use i2c_new_secondary_device() > >>>>>>>>>> so I removed it from the commit message. > >> > >> [...] > >> > >>>>>>>>>> .../devicetree/bindings/ge/b850v3-lvds-dp.txt | 39 +++++++++ > >>>>>>>>> > >>>>>>>>> Isn't '-lvds-dp' redundant? The part# should be enough. > >>>>>>>> > >>>>>>>> b850v3 is the name of the product, this is why the proposed name. > >>>>>>>> What about, b850v3-dp2 dp2 indicating the second DP output? > >>>>>>> > >>>>>> Humm, b850v3 is the board name? This node should be the name of > >>>>>>> the bridge chip. > >>>>>> > >>>>>> From the cover letter: > >>>>>> > >>>>>> -- // -- > >>>>>> There are two physical bridges on the video signal pipeline: a > >>>>>> STDP4028(LVDS to DP) and a STDP2690(DP to DP++). The hardware and > >>>>>> firmware made it complicated for this binding to comprise two > >>>>>> device tree nodes, as the design goal is to configure both bridges > >>>>>> based on the LVDS signal, which leave the driver powerless to control > >>>>>> the video processing pipeline. The two bridges behaves as a single > >>>>>> bridge, and the driver is only needed for telling the host about EDID > >>>>>> / HPD, and for giving the host powers to ack interrupts. The video > >>>>>> signal pipeline > >>>>>> > >>>>>> is as follows: > >>>>>> Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video > >>>>>> output > >>>>>> > >>>>>> -- // -- > >>>>> > >>>>> You forgot to prefix your patch series with [HACK] ;-) > >>>>> > >>>>> How about fixing the issues that make the two DT nodes solution > >>>>> difficult ? What are they ? > >>>> > >>>> The Firmware and the hardware design. Both bridges, with stock > >>>> firmware, are fully capable of providig EDID information and handling > >>>> interrupts. But on this specific design, with this specific firmware, I > >>>> need to read EDID from one bridge, and handle interrupts on the other. > >>> > >>> Which firmware are you talking about ? Firmware running on the > >>> bridges, or somewhere else ? > >> > >> Each bridge has it's own external flash containing a binary firmware. > >> The goal of the firmware is to configure the output end based on the > >> input end. This is part of what makes handling EDID and HPD challenging. > >> > >>>> Back when I was starting the development I could not come up with a > >>>> proper way to split EDID and interrupts between two bridges in a way > >>>> that would result in a fully functional connector. Did I miss > >>>> something? > >>> > >>> You didn't, we did :-) I've been telling for quite some time now that > >>> we must decouple bridges from connectors, and this is another example of > >>> why we have such a need. Bridges should expose additional functions > >>> needed to implement connector operations, and the connector should be > >>> instantiated by the display driver with the help of bridge operations. > >>> You could then create a connector that relies on one bridge to read the > >>> EDID and on the other bridge to handle HPD. > >> > >> Ah thanks. So for now the single DT node approach is acceptable, right? > >> The problem is that even if the driver is getting better on each > >> iteration, the single DT node for two chips issue comes back often and I > >> believe is _the_ issue preventing the driver from getting upstream. V1 > >> was sent ~ 8 months ago... > >> > >> Can I have some blessing on the single DT node approach for now? > > > > With the "DT as an ABI" approach, I'm afraid not. Temporary hacks are > > acceptable on the driver side, but you need two nodes in DT. > > So can I make two node DT "in the right way" and work around current > connectors vs. bridge limitations on the driver side? This seems to be > doable. > > Then I could fix bridge API, with my own driver and update API clients > affected by the change... I'm willing to discuss that as long as the DT bindings are correct, yes. > >> I'm one of the 3 proposed maintainers for the driver, and I'm willing to > >> maintain the driver on the long run, as is the same with the other two > >> proposed maintainers. So when the time to split the node in two comes, > >> we will be around, and willing to do it ourselves. > > > > How about putting that team of 3 maintainers to work on fixing the problem > > in the bridge API ? :-) > > Guess you would be a good lawyer! My point was not exactly that we could > work in parallel. Point was that there is redundancy in case one or two > of us loose interest. But nice try! :-) > > Chances of having resources to fix bridge API and clients were better 6 > months ago, but let me see what I can get. Last blocking issue was the > migration to atomic, now this. I'm going to need to answer what the next > blocking issue is going to be. > > Actually in these ~8 months one bit of the required changes was > accepted: dc80d7038883, but this was generic and not related to our > specific use case. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
