On Mon, Nov 14, 2016 at 8:11 PM, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hi Rob, > > On Monday 14 Nov 2016 19:40:26 Rob Herring wrote: >> On Mon, Oct 17, 2016 at 7:42 AM, Laurent Pinchart wrote: >> > On Friday 14 Oct 2016 07:40:14 Rob Herring wrote: >> >> On Sun, Oct 9, 2016 at 11:33 AM, Laurent Pinchart wrote: >> >>> On Saturday 08 Oct 2016 20:29:39 Rob Herring wrote: >> >>>> On Tue, Oct 04, 2016 at 07:23:29PM +0300, Laurent Pinchart wrote: >> >>>>> LVDS is a physical layer specification defined in ANSI/TIA/EIA-644-A. >> >>>>> Multiple incompatible data link layers have been used over time to >> >>>>> transmit image data to LVDS panels. This binding supports display >> >>>>> panels compatible with the JEIDA-59-1999, Open-LDI and VESA SWPG >> >>>>> specifications. [...] >> >>> Furthermore, LVDS data organization is controlled by the combination of >> >>> both data-mapping and data-mirror. It makes little sense from my point >> >>> of view to handle one as part of the compatible string and the other one >> >>> as a separate property. >> >>> >> >>>> > +Optional properties: >> >>>> > +- label: a symbolic name for the panel >> >>>> >> >>>> Could be for any panel or display connector. >> >>> >> >>> Yes, but I'm not sure to understand how that's relevant :-) >> >> >> >> Meaning it should be a common property. >> > >> > Sure. So you expect me to reorganize all the panels and connectors DT >> > bindings in order to get this one merged ? :-) >> >> No, because I don't think label is widely defined. Just put it in a >> common place and reference it. Any other panels can be fixed later. >> Really, the "simple panel" binding should probably morph into the >> common binding. > > The "label" property is actually defined in the "Devicetree Specification, Yes, so is reg, interrupts, etc. but we still list when those are used. > Release 0.1" as recently published on devicetree.org. Where would you like me > to define it in the bindings ? Just split things into 2 files. Move everything that's used in other panel bindings (label, width-mm, ports, etc.) to a panel/common.txt. Then in lvds-panel.txt, it just refers to common.txt and is just the LVDS specific things. Bonus points if simple-panel (should just go away), panel-dpi, panel-dsi-cm are converted. >> >>>>> +- avdd-supply: reference to the regulator that powers the panel >> >>>>> analog supply >> >>>>> +- dvdd-supply: reference to the regulator that powers the panel >> >>>>> digital supply I would not be against these being common either. It's somewhat better than simple-panel's "power-supply" property. >> >>>> >> >>>> Which one has to be powered on first, what voltage, and with what time >> >>>> in between? This is why "generic" or "simple" bindings don't work. >> >>> >> >>> The above-mentioned specifications also define connectors, pinouts and >> >>> power supplies, but many LVDS panels compatible with the LVDS physical >> >>> and data layers use a different connector with small differences in >> >>> power supplies. >> >>> >> >>> I believe the voltage is irrelevant here, it doesn't need to be >> >>> controlled by the operating system. Power supplies order and timing is >> >>> relevant, I'll investigate the level of differences between panels. I'm >> >>> also fine with dropping those properties for now. >> >> >> >> Whether you have control of the supplies is dependent on the board. >> >> Dropping them is just puts us in the simple binding trap. The simple >> >> bindings start out that way and then people keep adding to them. >> > >> > Damn, you can't be fooled easily ;-) >> >> I guess you can count all the simple bindings to see how many times I >> can be fooled. :) >> >> > On a more serious note, I'd like to design the bindings in a way that >> > wouldn't require adding device-specific code in the driver for each panel >> > model, given that in most cases power supply handling will be generic. >> > What's your opinion about a generic power supply model that would be used >> > in the default case, with the option to override it with device-specific >> > code when needed ? >> >> I don't agree. Read Thierry's post on the subject[1]. > > I'm not sure you understood me correctly (and writing a clarification at > 4:00am might not help :-)). My point here is that a fair number of panels > don't care about power sequencing and have no control GPIOs (that's certainly > the case of the two Mitsubishi panels I use here that have a single power > supply - good luck trying to convince me that this needs to be sequenced :-) - > and no enable or reset control pin). This kind of panel should obviously be > modelled in DT with both a specific and a generic ("panel-lvds") compatible > string, to ensure that we'll have enough information available on the > operating system side to control the panel properly. The power supply(ies) > should be documented in relation to the specific compatible string and not > mentioned by the generic bindings (whether that should go in one or multiple > text files is bikeshedding). Let me rephrase, I don't agree with generic bindings, but I fully support having a generic driver. So you can have a generic driver function that can handle your case. Even slightly more complicated can be handled: turn on all the supplies listed, de-assert any reset gpios, assert any enable gpios (this is why I push for common naming of "enable-gpios"). If this is enough for a panel, then the generic compatible will work. If not, sorry, provide your own power sequencing code and match on the more specific compatible. > This being said, on the driver side, I don't see a reason to list the specific > compatible strings explicitly for those panels when a generic implementation > matching the generic compatible string can handle them fine. This has no > impact on the bindings and is an Linux implementation decision. I think we're in agreement. Rob -- 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