Hi Laurent,

On Thu, Mar 19, 2020 at 1:04 PM Laurent Pinchart
[off-list ref] wrote:

Hi Maxime,

On Thu, Mar 19, 2020 at 01:44:52PM +0100, Maxime Ripard wrote:

quoted

On Fri, Mar 13, 2020 at 09:12:31PM +0000, Lad Prabhakar wrote:

quoted

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@bp.renesas.com>
---
 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 ?

Cheers,
--Prabhakar

quoted

If you want to retrieve that through the clock framework, then just
making clock-frequency optional is enough and falling back to
clk_get_rate on the clocks property already provided is enough.

--
Regards,

Laurent Pinchart

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