Hi Rob, On Thursday, 5 April 2018 19:33:33 EEST Rob Herring wrote: > On Mon, Apr 2, 2018 at 8:36 AM, Laurent Pinchart wrote: > > On Tuesday, 27 March 2018 14:03:25 EEST Vladimir Zapolskiy wrote: > >> On 03/27/2018 01:10 PM, jacopo mondi wrote: > >>> On Tue, Mar 27, 2018 at 12:37:31PM +0300, Vladimir Zapolskiy wrote: > >>>> On 03/27/2018 11:57 AM, jacopo mondi wrote: > >>>>> On Tue, Mar 27, 2018 at 11:30:29AM +0300, Vladimir Zapolskiy wrote: > >>>>>> On 03/27/2018 11:27 AM, Sergei Shtylyov wrote: > >>>>>>> On 3/27/2018 10:33 AM, jacopo mondi wrote: > >>>>>>> [...] > >>>>>>> > >>>>>>>>>>>>> Document Thine THC63LVD1024 LVDS decoder device tree > >>>>>>>>>>>>> bindings. > >>>>>>>>>>>>> > >>>>>>>>>>>>> Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx> > >>>>>>>>>>>>> Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx> > >>>>>>>>>>>>> Reviewed-by: Niklas Söderlund > >>>>>>>>>>>>> <niklas.soderlund+renesas@xxxxxxxxxxxx> > >>>>>>>>>>>>> --- > >>>>>>>>>>>>> > >>>>>>>>>>>>> .../bindings/display/bridge/thine,thc63lvd1024.txt | 66 +++ > >>>>>>>>>>>>> 1 file changed, 66 insertions(+) > >>>>>>>>>>>>> create mode 100644 > >>>>>>>>>>>>> > >>>>>>>>>>>>> Documentation/devicetree/bindings/display/bridge/thine,thc63l > >>>>>>>>>>>>> vd1024.txt > >>>>>>>>>>>>> diff --git > >>>>>>>>>>>>> a/Documentation/devicetree/bindings/display/bridge/thine,thc6 > >>>>>>>>>>>>> 3lvd1024.txt > >>>>>>>>>>>>> b/Documentation/devicetree/bindings/display/bridge/thine,thc6 > >>>>>>>>>>>>> 3lvd1024.txt > >>>>>>>>>>>>> new file mode 100644 > >>>>>>>>>>>>> index 0000000..8225c6a > >>>>>>>>>>>>> --- /dev/null > >>>>>>>>>>>>> +++ > >>>>>>>>>>>>> b/Documentation/devicetree/bindings/display/bridge/thine,thc6 > >>>>>>>>>>>>> 3lvd1024.txt > >>>>>>>>>>>>> @@ -0,0 +1,66 @@ > >>>>>>>>>>>>> +Thine Electronics THC63LVD1024 LVDS decoder > >>>>>>>>>>>>> +------------------------------------------- > >>>>>>>>>>>>> + > >>>>>>>>>>>>> +The THC63LVD1024 is a dual link LVDS receiver designed to > >>>>>>>>>>>>> convert LVDS streams > >>>>>>>>>>>>> +to parallel data outputs. The chip supports single/dual > >>>>>>>>>>>>> input/output modes, > >>>>>>>>>>>>> +handling up to two two input LVDS stream and up to two > >>>>>>>>>>>>> digital CMOS/TTL outputs. > >>>>>>>>>>>>> + > >>>>>>>>>>>>> +Single or dual operation modes, output data mapping and DDR > >>>>>>>>>>>>> output modes are > >>>>>>>>>>>>> +configured through input signals and the chip does not > >>>>>>>>>>>>> expose any control bus. > >>>>>>>>>>>>> + > >>>>>>>>>>>>> +Required properties: > >>>>>>>>>>>>> +- compatible: Shall be "thine,thc63lvd1024" > >>>>>>>>>>>>> + > >>>>>>>>>>>>> +Optional properties: > >>>>>>>>>>>>> +- vcc-supply: Power supply for TTL output and digital > >>>>>>>>>>>>> circuitry > >>>>>>>>>>>>> +- cvcc-supply: Power supply for TTL CLOCKOUT signal > >>>>>>>>>>>>> +- lvcc-supply: Power supply for LVDS inputs > >>>>>>>>>>>>> +- pvcc-supply: Power supply for PLL circuitry > >>>>>>>>>>>> > >>>>>>>>>>>> As explained in a comment to one of the previous versions of > >>>>>>>>>>>> this series, I'm tempted to make vcc-supply mandatory and drop > >>>>>>>>>>>> the three other power supplies for now, as I believe there's > >>>>>>>>>>>> very little chance they will be connected to separately > >>>>>>>>>>>> controllable regulators (all supplies use the same voltage). In > >>>>>>>>>>>> the very unlikely event that this occurs in design we need to > >>>>>>>>>>>> support in the future, the cvcc, lvcc and pvcc supplies can be > >>>>>>>>>>>> added later as optional without breaking backward > >>>>>>>>>>>> compatibility. > >>>>>>>>>>> > >>>>>>>>>>> I'm okay with that. > >>>>>>>>>>> > >>>>>>>>>>>> Apart from that, > >>>>>>>>>>>> > >>>>>>>>>>>> Reviewed-by: Laurent Pinchart > >>>>>>>>>>>> <laurent.pinchart@xxxxxxxxxxxxxxxx> > >>>>>>>>>>>> > >>>>>>>>>>>>> +- pdwn-gpios: Power down GPIO signal. Active low > >>>>>>>>>>> > >>>>>>>>>>> powerdown-gpios is the semi-standard name. > >>>>>>>>>> > >>>>>>>>>> right, I've also noticed it. If possible please avoid > >>>>>>>>>> shortenings in property names. > >>>>>>>>> > >>>>>>>>> It is not shortening, it just follow pin name from decoder's > >>>>>>>>> datasheet. > >>>>>>>>> > >>>>>>>>>>>>> +- oe-gpios: Output enable GPIO signal. Active high > >>>>>>>>>>>>> + > >>>>>>>>>> > >>>>>>>>>> And this one is also a not ever met property name, please > >>>>>>>>>> consider to rename it to 'enable-gpios', for instance display > >>>>>>>>>> panels define it. > >>>>>>>>> > >>>>>>>>> Again, it follows datasheet naming scheme. Has something changed > >>>>>>>>> in DT conventions? > >>>>>>>> > >>>>>>>> Seconded. My understanding is that the property name should > >>>>>>>> reflect what reported in the the chip manual. For THC63LVD1024 the > >>>>>>>> enable and power down pins are named 'OE' and 'PDWN' respectively. > >>>>>>> > >>>>>>> But don't we need the vendor prefix in the prop names then, like > >>>>>>> "renesas,oe-gpios" then? > >>>>>> > >>>>>> Seconded, with a correction to "thine,oe-gpios". > >>>>> > >>>>> mmm, okay then... > >>>>> > >>>>> A grep for that semi-standard properties names in Documentation/ > >>>>> returns only usage examples and no actual definitions, so I assume > >>>>> this is why they are semi-standard. > >>>> > >>>> Here we have to be specific about a particular property, let it be > >>>> 'oe-gpios' vs. 'enable-gpios' and let's collect some statistics: > >>>> > >>>> % grep -Hr oe-gpios Documentation/devicetree/bindings/* | wc -l > >>>> 0 > >>>> > >>>> $ grep -Hr enable-gpios Documentation/devicetree/bindings/* | wc -l > >>>> 86 > >>>> > >>>> While 'thine,oe-gpios' would be correct, I see no reason to introduce > >>>> a vendor specific property to define a pin with a common and well > >>>> understood purpose. > >>>> > >>>> If you go forward with the vendor specific prefix, apparently you can > >>>> set the name to 'thine,oe-gpio' (single) or even to 'thine,oe', or does > >>>> the datasheet names the pin as "OE GPIO" or "OE connected to a GPIO"? I > >>>> guess no. > >>> > >>> Let me clarify I don't want to push for a vendor specific name or > >>> similar, I'm fine with using 'semi-standard' names, I'm just confused > >>> by the 'semi-standard' definition. I guess from your examples, the > >>> usage count makes a difference here. > >> > >> yes, in gneneral you can read "semi-standard" as "widely used", thus > >> collecting statistics is a good enough method to make a reasoning. > >> > >> Hopefully the next evolutionary step of "widely used" is "described in > >> standard". > >> > >>>> Standards do not define '-gpios' suffix, but partially the description > >>>> is found in Documentation/bindings/gpio/gpio.txt, still it is not a > >>>> section in any standard as far as I know. > >>>> > >>>>> Seems like there is some tribal knowledge involved in defining what > >>>>> is semi-standard and what's not, or are those properties documented > >>>>> somewhere? > >>>> > >>>> The point is that there is no formal standard which describes every > >>>> IP, every IC and every single their property, some device node names > >>>> and property names are recommended in ePAPR and Devicetree > >>>> Specification though. > >>>> > >>>> Think of a confusion if 'rst-gpios' (have you seen any ICs with an RST > >>>> pin?) and 'reset-gpios' are different. Same applies to 'pdwn-gpios' > >>>> vs. 'powerdown-gpios'. > >>> > >>> I see all your points and I agree with most of them. Anyway, if the > >>> chip manual describes a pin as 'RST' I would not find it confusing to > >>> have a 'rst-gpio' defined in bindings :) > >>> > >>> Let me be a bit pesky here: what if a chip defines a reset GPIO, which > >>> is definitely a reset, but names it, say "XYZ" ? Would you prefer to > >>> see it defined as "reset-gpios" for consistency with other bindings, > >>> or "xyz-gpios" for consistency with documentation? > >> > >> If a pin is definitely an IC reset as you said, then my preference is to > >> see it described under 'reset-gpios' property name, plus a comment in > >> the IC device tree documentation document about it. I can provide two > >> reasons to advocate my position: > >> > >> 1) developers spend significantly more time reading and editing the > >> actual > >> > >> DTSI/DTS board files rather than reading and editing documentation, > >> it makes sense to use common property names to save time and reduce > >> amount of "what does 'oe' stand for?" type of questions; I suppose > >> that the recommendation to avoid not "widely used" abbreviations in > >> device node and property names arises from the same reasoning, > >> > >> 2) "widely used" and "standard" properties are excellent candidates for > >> > >> developing (or re-using) generalization wrappers, it happened so many > >> times in the past, and this process shall be supported in my opinion; > >> due to compatibility restrictions it might be problematic to change > >> property names, and every new exception to "widely used" properties > >> makes problematic to develop and maintain these kinds of wrappers, and > >> of course it postpones a desired "described in standard" recognition. > >> > >> If my point of view is accepted, I do admit that a developer who > >> translates a board schematics to board DTS file may experience a minor > >> discomfort, which is mitigated if relevant pin names are found in device > >> tree binding documentation in comments to properties, still the overall > >> gain is noticeably higher in my personal opinion. > > > > I have to disagree with this. When using a property name that doesn't > > correspond to the hardware documentation, developers will need to refer to > > the DT bindings documentation to confirm the property name. "Widely used" > > property names will not save time, they will use more time. This is of > > course marginal and I don't think it would have any noticeable impact, > > but I don't think your argument holds. > > We can have it both ways. The name should follow the documented > name/function. For example, we have enable-gpios which is simply the > invert of powerdown-gpios (for software's purposes). Pick the one > closest to the documentation. We're not trying to make bindings use > "enable" if a signal is called "powerdown". > > What we don't want is gratuitous variation in the names based on the > whims of hw designers: > > resetb-gpios > resetn-gpios > rst-gpios > rstn-gpios > nRESET-gpios > > ...you get the idea (and I left out vendor prefixes). Do we have a list of standardized names that should be used preferentially ? If not, should we create one ? > > I'm all for standardizing properties across DT bindings for multiple > > components, but doing so in a semi-random fashion will in my opinion not > > result in any gain. We can decide that power-down or output-enable GPIOS > > should have common property names (and I'm not even sure that would be > > useful, but we can certainly discuss it), but in that case someone should > > make a proposal and get the names standardized. Unless we do so, no > > matter what property name gets picked for a particular binding, it won't > > become universally used by magic. > > For "output enable", I suspect that is a common signal/function and > should have a standardized name. Generally, the way this works is we > get several variations and then we try to standardize things. I think > we can all agree standardizing first is better. If you want to put it > in a common place, please do. Maybe people will read that. Regardless, > the only way to enforce following standard names is with review. > > Debating "oe" vs. "output-enable" is bikeshedding IMO. Anyone familiar > with h/w design should recognize OE. > > The reason to try and standardize names is so we can have common > drivers or library functions. In particular, for things like GPIOs > that need to be configured first for devices on otherwise discoverable > buses, this is very useful. I'm not sure we will ever implement that for the OE or power-down GPIOs, but I'm also not sure we will never do it, so I suppose it makes sense, just in 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
