On Fri, Dec 08, 2023 at 08:37:10PM +0100, Krzysztof Kozlowski wrote:
> On 08/12/2023 19:07, Sakari Ailus wrote:
> > Hi Krzysztof,
> >
> > Thanks for the update.
> >
> > On Thu, Dec 07, 2023 at 03:23:56PM +0100, Krzysztof Kozlowski wrote:
> >> The data lanes and link frequency were set to match exiting Linux driver
> >> limitations, however bindings should be independent of chosen Linux
> >> driver support.
> >>
> >> Decouple these properties from the driver to match what is actually
> >> supported by the hardware.
> >>
> >> This also fixes DTS example:
> >>
> >> ov8856.example.dtb: camera@10: port:endpoint:link-frequencies:0: [360000000] is too short
> >>
> >> Fixes: 066a94e28a23 ("media: dt-bindings: media: Use graph and video-interfaces schemas")
> >> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> >>
> >> ---
> >>
> >> Changes in v2:
> >> 1. Rework approach: decouple bindings from driver instead of fixing
> >> DTS example (Sakari)
> >> ---
> >> .../devicetree/bindings/media/i2c/ov8856.yaml | 21 +++++++++++--------
> >> 1 file changed, 12 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/media/i2c/ov8856.yaml b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> >> index 57f5e48fd8e0..71102a71cf81 100644
> >> --- a/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> >> +++ b/Documentation/devicetree/bindings/media/i2c/ov8856.yaml
> >> @@ -67,19 +67,22 @@ properties:
> >>
> >> properties:
> >> data-lanes:
> >> - description: |-
> >> - The driver only supports four-lane operation.
> >> - items:
> >> - - const: 1
> >> - - const: 2
> >> - - const: 3
> >> - - const: 4
> >> + oneOf:
> >> + - items:
> >> + - const: 1
> >> + - items:
> >> + - const: 1
> >> + - const: 2
> >> + - items:
> >> + - const: 1
> >> + - const: 2
> >> + - const: 3
> >> + - const: 4
> >>
> >> link-frequencies:
> >> description: Frequencies listed are driver, not h/w limitations.
> >
> > This should be dropped, too.
>
> Ack, I forgot.
>
> >
> >> - maxItems: 2
> >> items:
> >> - enum: [ 360000000, 180000000 ]
> >> + enum: [ 1440000000, 720000000, 360000000, 180000000 ]
> >
> > These frequencies are listed in the datasheet but they're just an
> > example---the sensor hardware isn't limited to these, the resulting
> > frequency on the CSI-2 bus is simply up to the external clock frequency and
> > PLL configuration. I'd remove the values here altogether.
>
> Hm, are you sure? Isn't it quite difficult to program device to any
> frequency? But if that's not the case here, I can drop it.
The driver doesn't currently do that, no, but that doesn't mean the
hardware wouldn't support that. There are a few sensor drivers that
calculate the PLL configuration, such as ccs and ov5640.
I'd drop it as it's indeed a driver, not a device limitation.
--
Sakari Ailus
