On Tue, Sep 29, 2020 at 12:40:46PM +0300, Sakari Ailus wrote: > On Tue, Sep 29, 2020 at 11:18:46AM +0200, Krzysztof Kozlowski wrote: > > On Tue, 29 Sep 2020 at 11:15, Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> wrote: > > > > > > Hi Krzysztof, > > > > > > On Wed, Sep 23, 2020 at 05:21:26PM +0200, Krzysztof Kozlowski wrote: > > > > Add bindings for the IMX258 camera sensor. The bindings, just like the > > > > driver, are quite limited, e.g. do not support regulator supplies. > > > > > > > > Signed-off-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx> > > > > > > > > --- > > > > > > > > Changes since v3: > > > > 1. Document also two lane setup. > > > > > > > > Changes since v2: > > > > 1. Remove clock-frequency, add reset GPIOs, add supplies. > > > > > > Oops. I missed this one. > > > > > > How does the driver know the appropriate clock frequency for the platform > > > if it's not in DT? The sensor supports a range of frequencies, not a single > > > frequency. > > > > > > Could you add clock-frequency back? > > > > Not really, it was removed on Rob's request. The bindings do not > > describe driver's behavior so how the driver gets frequency should not > > be part of the bindings. Also it's not a real problem - the driver > > just calls clk_get_rate(). > > How is the rate determined? I mean, many ISPs or CSI-2 receivers that > provide the clock are also capable of using a variety of frequencies. But > only one can be used on the platform in general. Having "clock-frequency" property in DTS did not solve that. It has no effect on actual frequency. > > Where does it come from if it's not in DT? The frequency is either chosen by consumer (imx258) or pre-assigned from DT, but not with "clock-frequency" property. There are generic properties for this: assigned-clocks, assigned-clock-rates and assigned-clock-parents. These properties should be added to DTS if additionalProperties is false, which is the case here... so I could add them. My DTS anyway does not use them, as the clock is generated internally on a camera board so I don't have a control over it. Best regards, Krzysztof > > Using another frequency generally leads to failure later on as the desired > link frequency likely is not available for a random external clock > frequency.
