lkml.org 
[lkml]   [2020]   [Mar]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v3 1/4] media: dt-bindings: media: i2c: Switch to assigned-clock-rates
Hi Laurent,

On Tue, Mar 24, 2020 at 4:12 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Prabhakar,
>
> On Tue, Mar 24, 2020 at 04:04:43PM +0000, Lad, Prabhakar wrote:
> > On Tue, Mar 24, 2020 at 3:40 PM Maxime Ripard <maxime@cerno.tech> wrote:
> > > On Thu, Mar 19, 2020 at 01:17:51PM +0000, Lad, Prabhakar wrote:
> > > > On Thu, Mar 19, 2020 at 1:04 PM Laurent Pinchart wrote:
> > > > > 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@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 ?
> > >
> > > 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.
> >
> > Thank you for the clarification, Ill drop patches 1-4 from this series.
>
> That's the whole series... :-) I think you should keep patch 1/4 but
> just remove the clock-frequency from the bindings, then remove it from
> the DT files, and patch the driver to set the clock rate to 24MHz
> unconditionally in patch 4/4.
>
My bad I was referring to v4 series patch 5/5 which converts dt
bindings to json schema.
I'll shall post a v5 as suggested above.

Cheers,
--Prabhakar

> --
> Regards,
>
> Laurent Pinchart

\
 
 \ /
  Last update: 2020-03-25 22:53    [W:0.049 / U:8.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site