From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>, Fabio Estevam <festevam@gmail.com>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
Shawn Guo <shawnguo@kernel.org>,
Sascha Hauer <s.hauer@pengutronix.de>,
Magnus Damm <magnus.damm@gmail.com>,
Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
Rob Herring <robh+dt@kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Maxime Ripard <maxime@cerno.tech>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
NXP Linux Team <linux-imx@nxp.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Ezequiel Garcia <ezequiel@collabora.com>,
LAK <linux-arm-kernel@lists.infradead.org>,
linux-media <linux-media@vger.kernel.org>
Subject: Re: [PATCH v3 1/4] media: dt-bindings: media: i2c: Switch to assigned-clock-rates
Date: Tue, 24 Mar 2020 18:12:21 +0200 [thread overview]
Message-ID: <20200324161221.GA27805@pendragon.ideasonboard.com> (raw)
In-Reply-To: <CA+V-a8tMVoJOdgM_S0sJ0WEGhwBirCC4mi-TtxLCn1SKVXXiBQ@mail.gmail.com>
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.
--
Regards,
Laurent Pinchart
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-03-24 16:13 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 21:12 [PATCH v3 0/4] ov5645: Switch to assigned-clock-rates Lad Prabhakar
2020-03-13 21:12 ` [PATCH v3 1/4] media: dt-bindings: media: i2c: " Lad Prabhakar
2020-03-13 21:20 ` Laurent Pinchart
2020-03-13 21:25 ` Prabhakar Mahadev Lad
2020-03-13 21:27 ` Laurent Pinchart
2020-03-18 20:13 ` Lad, Prabhakar
2020-03-18 22:33 ` Laurent Pinchart
2020-03-18 22:37 ` Lad, Prabhakar
2020-03-19 12:44 ` Maxime Ripard
2020-03-19 13:03 ` Laurent Pinchart
2020-03-19 13:17 ` Lad, Prabhakar
2020-03-24 15:40 ` Maxime Ripard
2020-03-24 16:04 ` Lad, Prabhakar
2020-03-24 16:12 ` Laurent Pinchart [this message]
2020-03-25 21:52 ` Lad, Prabhakar
2020-03-19 13:05 ` Lad, Prabhakar
2020-03-13 21:12 ` [PATCH v3 2/4] media: i2c: ov5645: " Lad Prabhakar
2020-03-13 21:16 ` Laurent Pinchart
2020-03-13 21:19 ` Prabhakar Mahadev Lad
2020-03-13 21:12 ` [PATCH v3 3/4] media: i2c: ov5645: Set maximum leverage of external clock frequency to 24480000 Lad Prabhakar
2020-03-13 21:23 ` Laurent Pinchart
2020-03-13 21:31 ` Prabhakar Mahadev Lad
2020-03-18 22:41 ` Lad, Prabhakar
2020-03-18 23:22 ` Laurent Pinchart
2020-03-19 8:00 ` Lad, Prabhakar
2020-03-18 23:18 ` Laurent Pinchart
2020-03-19 7:59 ` Lad, Prabhakar
2020-03-13 21:12 ` [PATCH v3 4/4] ARM: dts: imx6qdl-wandboard: Switch to assigned-clock-rates for ov5645 node Lad Prabhakar
2020-03-13 21:25 ` Laurent Pinchart
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200324161221.GA27805@pendragon.ideasonboard.com \
--to=laurent.pinchart@ideasonboard.com \
--cc=devicetree@vger.kernel.org \
--cc=ezequiel@collabora.com \
--cc=festevam@gmail.com \
--cc=geert@linux-m68k.org \
--cc=kernel@pengutronix.de \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-imx@nxp.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=magnus.damm@gmail.com \
--cc=mark.rutland@arm.com \
--cc=maxime@cerno.tech \
--cc=mchehab@kernel.org \
--cc=prabhakar.csengg@gmail.com \
--cc=prabhakar.mahadev-lad.rj@bp.renesas.com \
--cc=robh+dt@kernel.org \
--cc=s.hauer@pengutronix.de \
--cc=sakari.ailus@linux.intel.com \
--cc=shawnguo@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).