Hello Hans, Do you have any further feedback on this? Thanks, Chris > From: Ramesh Shanmugasundaram > Sent: 10 January 2017 09:31 > Hi Laurent, > > > > >>> On Wednesday 21 Dec 2016 08:10:37 Ramesh Shanmugasundaram > wrote: > > > >>>> Add binding documentation for Renesas R-Car Digital Radio > > > >>>> Interface > > > >>>> (DRIF) controller. > > > >>>> > > > >>>> Signed-off-by: Ramesh Shanmugasundaram > > > >>>> <ramesh.shanmugasundaram@xxxxxxxxxxxxxx> --- > > > >>>> > > > >>>> .../devicetree/bindings/media/renesas,drif.txt | 202 > > +++++++++++++ > > > >>>> 1 file changed, 202 insertions(+) create mode 100644 > > > >>>> > > > >>>> Documentation/devicetree/bindings/media/renesas,drif.txt > > > >>>> > > > >>>> diff --git > > > >>>> a/Documentation/devicetree/bindings/media/renesas,drif.txt > > > >>>> b/Documentation/devicetree/bindings/media/renesas,drif.txt new > > > >>>> file mode 100644 index 0000000..1f3feaf > > > >>>> --- /dev/null > > > >>>> +++ b/Documentation/devicetree/bindings/media/renesas,drif.txt > > > >>>> > > > >>>> +Optional properties of an internal channel when: > > > >>>> + - It is the only enabled channel of the bond (or) > > > >>>> + - If it acts as primary among enabled bonds > > > >>>> +-------------------------------------------------------- > > > >>>> +- renesas,syncmd : sync mode > > > >>>> + 0 (Frame start sync pulse mode. 1-bit > > > >>>> +width > > > >>>> pulse > > > >>>> + indicates start of a frame) > > > >>>> + 1 (L/R sync or I2S mode) (default) > > > >>>> +- renesas,lsb-first : empty property indicates lsb bit is > > received > > > >>>> first. > > > >>>> + When not defined msb bit is received > > > >>>> +first > > > >>>> +(default) > > > >>>> +- renesas,syncac-active: Indicates sync signal polarity, 0/1 > > > >>>> +for > > > >>>> low/high > > > > > > Shouldn't this be 'renesas,sync-active' instead of syncac-active? > > > > > > I'm not sure if syncac is intended or if it is a typo. > > > > > > >>>> + respectively. The default is 1 (active high) > > > >>>> +- renesas,dtdl : delay between sync signal and start of > > > >>>> reception. > > > >>>> + The possible values are represented in > > > >>>> + 0.5 > > clock > > > >>>> + cycle units and the range is 0 to 4. The > > default > > > >>>> + value is 2 (i.e.) 1 clock cycle delay. > > > >>>> +- renesas,syncdl : delay between end of reception and sync > > > >>>> signal edge. > > > >>>> + The possible values are represented in > > > >>>> + 0.5 > > clock > > > >>>> + cycle units and the range is 0 to 4 & 6. > > > >>>> + The > > > >>>> default > > > >>>> + value is 0 (i.e.) no delay. > > > >>> > > > >>> Most of these properties are pretty similar to the video bus > > > >>> properties defined at the endpoint level in > > > >>> Documentation/devicetree/bindings/media/video-interfaces.txt. I > > > >>> believe it would make sense to use OF graph and try to > > > >>> standardize these properties similarly. > > > > > > Other than sync-active, is there really anything else that is similar? > > > And even the sync-active isn't a good fit since here there is only > > > one sync signal instead of two for video (h and vsync). > > > > That's why I said similar, not identical :-) My point is that, if we > > consider that we could connect multiple sources to the DRIF, using OF > > graph would make sense, and the above properties should then be > > defined per endpoint. > > Thanks for the clarifications. I have some questions. > > - Assuming two devices are interfaced with DRIF and they are represented > using two endpoints, the control signal related properties of DRIF might still > need to be same for both endpoints? For e.g. syncac-active cannot be > different in both endpoints? > > - I suppose "lsb-first", "dtdl" & "syncdl" may be defined per endpoint. > However, h/w manual says same register values needs to be programmed > for both the internal channels of a channel. Same with "syncmd" property. > > We could still define them as per endpoint property with a note that they > need to be same. But I am not sure if that is what you intended? > > If we define them per endpoint we should then also try > > standardize the ones that are not really Renesas-specific (that's at > > least syncac-active). > > OK. I will call it "sync-active". > > For the syncmd and lsb-first properties, it could also > > make sense to query them from the connected subdev at runtime, as > > they're similar in purpose to formats and media bus configuration > > (struct v4l2_mbus_config). > > May I know in bit more detail about what you had in mind? Please correct me > if my understanding is wrong here but when I looked at the code > > 1) mbus_config is part of subdev_video_ops only. I assume we don't want to > support this as part of tuner subdev. The next closest is pad_ops with "struct > v4l2_mbus_framefmt" but it is fully video specific config unless I come up > with new MEDIA_BUS_FMT_xxxx in media-bus-format.h and use the code > field? For e.g. > > #define MEDIA_BUS_FMT_SDR_I2S_PADHI_BE 0x7001 > #define MEDIA_BUS_FMT_SDR_I2S_PADHI_LE 0x7002 > > 2) The framework does not seem to mandate pad ops for all subdev. As the > tuner can be any third party subdev, is it fair to assume that these properties > can be queried from subdev? > > 3) Assuming pad ops is not available on the subdev shouldn't we still need a > way to define these properties on DRIF DT? > > > > > I'm not an SDR expert, so I'd like to have your opinion on this. > > > > > >> Note that the last two properties match the those in > > > >> Documentation/devicetree/bindings/spi/sh-msiof.txt. > > > >> We may want to use one DRIF channel as a plain SPI slave with the > > > >> (modified) MSIOF driver in the future. > > > > > > > > Should I leave it as it is or modify these as in video-interfaces.txt? > > > > Shall we conclude on this please? > > > > Thanks, > Ramesh
