From: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
To: Maxime Ripard <maxime@cerno.tech>
Cc: linux-media@vger.kernel.org, devicetree@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
linux-phy@lists.infradead.org, linux-clk@vger.kernel.org,
linux-staging@lists.linux.dev, Yong Deng <yong.deng@magewell.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Rob Herring <robh+dt@kernel.org>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
Hans Verkuil <hans.verkuil@cisco.com>,
Chen-Yu Tsai <wens@csie.org>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Helen Koike <helen.koike@collabora.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH 01/22] clk: sunxi-ng: v3s: Make the ISP PLL clock public
Date: Mon, 13 Sep 2021 10:53:51 +0200 [thread overview]
Message-ID: <YT8RnzVqLebtPMD+@aptenodytes> (raw)
In-Reply-To: <20210913075417.ampb2jt4quftpqzj@gilmour>
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Hi,
On Mon 13 Sep 21, 09:54, Maxime Ripard wrote:
> On Fri, Sep 10, 2021 at 08:41:26PM +0200, Paul Kocialkowski wrote:
> > In order to reparent the CSI module clock to the ISP PLL via
> > device-tree, export the ISP PLL clock declaration in the public
> > device-tree header.
>
> You use clk_set_rate_exclusive in the ISP driver on the module clock so
> it should prevent what you're mentioning from happening.
It does, but then it breaks display support entirely (because the DRM
driver doesn't use clk_set_rate_exclusive).
The bottomline is that using the same PLL for both display and camera
easily results in conflicts.
> If it doesn't, then clk_set_rate_exclusive has a bug and should be
> fixed.
>
> Either way, using assigned-clock-parents is not a good solution here
> either, it only makes sure that this is the case when probe is run.
I'm not sure what could provide better guarantees. There is a clock
parenting API (in the clock framework) which may, but this implies
providing the parent clock to the driver which seems way out of line
since this is a platform-specific matter that should certainly not
be handled by the driver.
I also tried hardcoding the reparenting bit in the CCU driver, but
this felt less clean than doing it in device-tree.
What do you think?
> > Details regarding why the CSI module clock is best parented to the ISP
> > PLL are provided in the related commit.
>
> This is relevant to this commit too and "the related commit" is far too
> blurry when you consider the entire Linux git history.
Fair enough!
Cheers,
Paul
--
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
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next prev parent reply other threads:[~2021-09-13 8:53 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-10 18:41 [PATCH 00/22] Allwinner A31/A83T MIPI CSI-2 Support and A31 ISP Support Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 01/22] clk: sunxi-ng: v3s: Make the ISP PLL clock public Paul Kocialkowski
2021-09-13 7:54 ` Maxime Ripard
2021-09-13 8:53 ` Paul Kocialkowski [this message]
2021-09-16 16:30 ` Maxime Ripard
2021-09-10 18:41 ` [PATCH 02/22] ARM: dts: sun8i: v3s: Parent the CSI module clock to the ISP PLL Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 03/22] dt-bindings: sun6i-a31-mipi-dphy: Add optional direction property Paul Kocialkowski
2021-09-13 8:00 ` Maxime Ripard
2021-09-14 7:39 ` Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 04/22] phy: allwinner: phy-sun6i-mipi-dphy: Support D-PHY Rx mode for MIPI CSI-2 Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 05/22] dt-bindings: media: sun6i-a31-csi: Add MIPI CSI-2 input port Paul Kocialkowski
2021-09-13 8:09 ` Maxime Ripard
2021-09-14 7:43 ` Paul Kocialkowski
2021-09-14 12:06 ` Maxime Ripard
2021-09-10 18:41 ` [PATCH 06/22] dt-bindings: media: Add Allwinner A31 MIPI CSI-2 bindings documentation Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 07/22] media: sunxi: Add support for the A31 MIPI CSI-2 controller Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 08/22] MAINTAINERS: Add entry for the Allwinner A31 MIPI CSI-2 bridge driver Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 09/22] ARM: dts: sun8i: v3s: Add nodes for MIPI CSI-2 support Paul Kocialkowski
2021-09-11 2:32 ` Samuel Holland
2021-09-13 7:44 ` Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 10/22] dt-bindings: media: Add Allwinner A83T MIPI CSI-2 bindings documentation Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 11/22] media: sunxi: Add support for the A83T MIPI CSI-2 controller Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 12/22] MAINTAINERS: Add entry for the Allwinner A83T MIPI CSI-2 bridge Paul Kocialkowski
2021-09-10 18:41 ` [PATCH NOT FOR MERGE 13/22] ARM: dts: sun8i: a83t: Add MIPI CSI-2 controller node Paul Kocialkowski
2021-09-11 2:53 ` Chen-Yu Tsai
2021-09-13 7:45 ` Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 14/22] ARM: dts: sun8i: a83t: bananapi-m3: Enable MIPI CSI-2 with OV8865 Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 15/22] media: sunxi: Remove the sun6i-csi driver implementation Paul Kocialkowski
2021-09-13 8:17 ` Maxime Ripard
2021-09-14 8:04 ` Paul Kocialkowski
2021-09-15 19:51 ` Sakari Ailus
2021-09-10 18:41 ` [PATCH 16/22] media: sunxi: Introduce a rewritten sun6i-csi driver Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 17/22] dt-bindings: media: Add Allwinner A31 ISP bindings documentation Paul Kocialkowski
2021-09-13 8:18 ` Maxime Ripard
2021-09-14 7:44 ` Paul Kocialkowski
2021-09-14 12:07 ` Maxime Ripard
2021-09-10 18:41 ` [PATCH 18/22] dt-bindings: media: sun6i-a31-csi: Add ISP output port Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 19/22] soc: sunxi: mbus: Add A31 ISP compatibles to the list Paul Kocialkowski
2021-09-11 2:36 ` Samuel Holland
2021-09-13 7:45 ` Paul Kocialkowski
2021-09-13 8:32 ` Maxime Ripard
2021-09-10 18:41 ` [PATCH 20/22] staging: media: Add support for the Allwinner A31 ISP Paul Kocialkowski
2021-09-13 8:31 ` Maxime Ripard
2021-09-14 7:50 ` Paul Kocialkowski
2021-09-14 11:11 ` Laurent Pinchart
2021-09-14 11:48 ` Maxime Ripard
2021-09-10 18:41 ` [PATCH 21/22] MAINTAINERS: Add entry for the Allwinner A31 ISP driver Paul Kocialkowski
2021-09-10 18:41 ` [PATCH 22/22] ARM: dts: sun8i: v3s: Add support for the ISP Paul Kocialkowski
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