Hi Maxime, On Thursday 01 Dec 2016 10:13:13 Maxime Ripard wrote: > On Wed, Nov 30, 2016 at 12:12:55PM +0200, Laurent Pinchart wrote: > >> More, it is not sure that the bridge/DW code would work with Allwinner's > >> SoCs. > > > > If it doesn't work and can't be made to work in a non-invasive way they it > > should certainly not be used :-) > > Even if the register layout is completely scrambled, as long as the > bits themselves aren't (and by comparing the two drivers it looks like > they haven't changed), you can easily deal with that using the > regmap_fields, with the two implementations (the original one and the > scrambled one) providing their register map that way, and the driver > code using whatever has been provided. Looking at https://linux-sunxi.org/DWC_HDMI_Controller#DWC_HDMI_Controller it seems that an address remapping function could be used. > >> Eventually, I went the same way as omap/hdmi5: different driver. > > > > I might try to fix that for OMAP5 at some point, we'll see. > > For complex drivers that have already a driver written and a lot of > testing that already happened, I don't think duplication is a smart > move. > > >>> - And finally the fact that we can't have several display engine in > >>> parallel, if needs be. This has happened in the past already on > >>> Allwinner SoCs, so it's definitely something we should consider in > >>> the DT bindings, since we can't break them. > >> > >> IIRC, I proposed my driver before yours, and the DE2 is completely > >> different from the other display engines. > >> What you are telling is "add more code to already complex code and have > >> a big driver for all SoCs in each kernels". > >> I think it should be better to have small modules, each one treating > >> specific hardware, and to let only the needed code in the kernel memory > >> at startup time. > >> > >>> Until those are fixed, I cannot see how this driver can be merged, > >>> unfortunately. > >> > >> No problem. I just wanted to help people by giving the job I did on the > >> boards I have. My boards are working for almost one year, fine enough > >> for I use them as daily desktop computers. I don't want to spend one > >> more year for having my code in the Linux kernel: there are so much > >> other exciting things to do... > > > > And you're certainly welcome to contribute drivers to the kernel, that's > > always appreciated. Of course, to ensure a reasonable level of quality and > > consistency between drivers, the review process often requires changes to > > be made to the code being submitted. When it comes to drivers I mostly > > pay attention to DT bindings, userspace APIs and modification to common > > code. Driver code itself, as long as it's reasonably clean and doesn't > > impede development of other drivers or impact system security in an > > adverse way, is still important but maybe slightly less so. I'll defer to > > Maxime to come to an agreement on the multiple display engines in > > parallel problem as I'm not familiar with it for the Allwinner platforms. > > The earlier Allwinner SoCs (with the old display engine), we had some > SoCs with multiple instances of the display engine and TCON (the > display engine roughly implementing the planes, the TCON the > CRTC. Roughly.). However, those were sharing some encoders (HDMI, > DSI) after that. > > So we need to have a single DRM device taking care of the multiple > display engines, which essentialy means that we have to decouple the > DRM device from the display engine. This was done in the earlier > designs using an additional node with a list of phandles to the > display engines in the system, and obviously, I'd prefer to have some > consistency and reuse the same thing. > > But the current approach doesn't work and will require some DT > modifications if that case happens again, which we can't do because of > the DT ABI. -- 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
