Hi Marco, On Fri, Mar 01, 2019 at 02:01:18PM +0100, Marco Felsch wrote: > Hi Ian, > > On 19-03-01 11:07, Ian Arkver wrote: > > Hi, > > > > On 01/03/2019 10:52, Marco Felsch wrote: > > > Hi Sakari, > > > > > > On 19-02-18 12:03, Sakari Ailus wrote: > > > > Hi Marco, > > > > > > > > My apologies for reviewing this so late. You've received good comments > > > > already. I have a few more. > > > > > > Thanks for your review for the other patches as well =) Sorry for my > > > delayed response. > > > > > > > On Tue, Dec 18, 2018 at 03:12:38PM +0100, Marco Felsch wrote: > > > > > Add corresponding dt-bindings for the Toshiba tc358746 device. > > > > > > > > > > Signed-off-by: Marco Felsch <m.felsch@xxxxxxxxxxxxxx> > > > > > --- > > > > > .../bindings/media/i2c/toshiba,tc358746.txt | 80 +++++++++++++++++++ > > > > > 1 file changed, 80 insertions(+) > > > > > create mode 100644 Documentation/devicetree/bindings/media/i2c/toshiba,tc358746.txt > > > > > > > > > > diff --git a/Documentation/devicetree/bindings/media/i2c/toshiba,tc358746.txt b/Documentation/devicetree/bindings/media/i2c/toshiba,tc358746.txt > > > > > new file mode 100644 > > > > > index 000000000000..499733df744a > > > > > --- /dev/null > > > > > +++ b/Documentation/devicetree/bindings/media/i2c/toshiba,tc358746.txt > > > > > @@ -0,0 +1,80 @@ > > > > > +* Toshiba TC358746 Parallel to MIPI CSI2-TX or MIPI CSI2-RX to Parallel Bridge > > > > > + > > > > > +The Toshiba TC358746 is a bridge that converts a Parallel-in stream to MIPI CSI-2 TX > > > > > +or a MIPI CSI-2 RX stream into a Parallel-out. It is programmable through I2C. > > > > > > > > This is interesting. The driver somehow needs to figure out the direction > > > > of the data flow if it does not originate from DT. I guess it shouldn't as > > > > it's not the property of an individual device, albeit in practice in all > > > > hardware I've seen the direction of the pipeline is determinable and this > > > > is visible in the kAPI as well. So I'm suggesting no changes due to this in > > > > bindings, likely we'll need to address it somehow elsewhere going forward. > > > > > > What did you mean with "... and this is visible in the kAPI as well"? > > > I'm relative new in the linux-media world but I never saw a device which > > > supports two directions. Our customer which uses that chip use it > > > only in parallel-in/csi-out mode. To be flexible the switching should be > > > done by a subdev-ioctl but it is also reasonable to define a default value > > > within the DT. > > > > The mode is set by a pin strap at reset time (MSEL). It's not programmable > > by i2c. As far as I can see, looking at the registers, it's also not > > readable by i2c, so there's no easy way for a driver which supports both > > modes to see what the pinstrap is set to. > > > > I'm not sure if the driver could tell from the direction of the endpoints > > it's linked to which mode to use, but if not it'll need to be told somehow > > and a DT property seems reasonable to me. Given that the same pins are used > > in each direction I think the direction is most likely to be hard wired and > > board specific. > > You're absolutly right. Sorry didn't catched this, since it's a bit out of my > mind.. There 'can be' cases where the MSEL is connected to a GPIO but in > that case the device needs a hard reset to resample the pin. Also a > parallel-bus mux must be in front of the device. So I think that > 'danymic switching' case is currently out of scope. I'm with you to > define the mode by a DT property is absolutly okay, the property should > something like: > > (more device specific) > tc358746,default-mode = <CSI-Tx> /* Parallel-in -> CSI-out */ > tc358746,default-mode = <CSI-Rx> /* CSI-in -> Parallel-out */ > > or > > (more generic) > tc358746,default-dir = <PARALLEL_TO_CSI2> > tc358746,default-dir = <CSI2_TO_PARALLEL> The prefix for Toshiba is "toshiba". What would you think of "toshiba,csi2-direction" with values of either "rx" or "tx"? Or "toshiba,csi2-mode" with either "master" or "slave", which would be a little bit more generic, but could be slightly more probable to get wrong as well. -- Regards, Sakari Ailus sakari.ailus@xxxxxxxxxxxxxxx
