On Thu, Mar 19, 2020 at 01:17:51PM +0000, Lad, Prabhakar wrote: > Hi Laurent, > > On Thu, Mar 19, 2020 at 1:04 PM Laurent Pinchart > <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > > > > Hi Maxime, > > > > On Thu, Mar 19, 2020 at 01:44:52PM +0100, Maxime Ripard wrote: > > > On Fri, Mar 13, 2020 at 09:12:31PM +0000, Lad Prabhakar wrote: > > > > Use assigned-clock-rates to specify the clock rate. Also mark > > > > clock-frequency property as deprecated. > > > > > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx> > > > > --- > > > > Documentation/devicetree/bindings/media/i2c/ov5645.txt | 5 +++-- > > > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/Documentation/devicetree/bindings/media/i2c/ov5645.txt b/Documentation/devicetree/bindings/media/i2c/ov5645.txt > > > > index 72ad992..e62fe82 100644 > > > > --- a/Documentation/devicetree/bindings/media/i2c/ov5645.txt > > > > +++ b/Documentation/devicetree/bindings/media/i2c/ov5645.txt > > > > @@ -8,7 +8,7 @@ Required Properties: > > > > - compatible: Value should be "ovti,ov5645". > > > > - clocks: Reference to the xclk clock. > > > > - clock-names: Should be "xclk". > > > > -- clock-frequency: Frequency of the xclk clock. > > > > +- clock-frequency (deprecated): Frequency of the xclk clock. > > > > - enable-gpios: Chip enable GPIO. Polarity is GPIO_ACTIVE_HIGH. This corresponds > > > > to the hardware pin PWDNB which is physically active low. > > > > - reset-gpios: Chip reset GPIO. Polarity is GPIO_ACTIVE_LOW. This corresponds to > > > > @@ -37,7 +37,8 @@ Example: > > > > > > > > clocks = <&clks 200>; > > > > clock-names = "xclk"; > > > > - clock-frequency = <24000000>; > > > > + assigned-clocks = <&clks 200>; > > > > + assigned-clock-rates = <24000000>; > > > > > > > > vdddo-supply = <&camera_dovdd_1v8>; > > > > vdda-supply = <&camera_avdd_2v8>; > > > > > > clock-frequency is quite different from assigned-clock-rates though, > > > semantically speaking. clock-frequency is only about what the clock > > > frequency is, while assigned-clock-rates will change the rate as well, > > > and you have no idea how long it will last. > > > > The driver currently reads the clock-frequency property and then calls > > clk_set_rate(). I agree tht assigned-clock-rates isn't a panacea, but I > > think it's less of a hack than what we currently have. > > > > As discussed on IRC, maybe the best option in this specific case is to > > drop clock-frequency and assigned-clok-rates, and call clk_set_rate() > > with a hardcoded frequency of 24MHz in the driver, as that's the only > > frequency the driver supports. > > > Does this mean any driver which has a fixed clock requirement shouldn't be a > DT property and should be just handled by the drivers internally ? It's hard to give a generic policy, but here, the hardware is pretty flexible since it can deal with anything between 6MHz to 50-something MHz, it's the driver that chooses to enforce a 24MHz and be pedantic about it, so it's up to the driver to enforce that policy, not to the DT since it's essentially a software limitation, not a hardware one. Maxime
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