From: Rob Herring <robh@kernel.org>
To: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Frank Rowand <frowand.list@gmail.com>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@kernel.org>,
devicetree@vger.kernel.org, linux-clk@vger.kernel.org,
linux-renesas-soc@vger.kernel.org,
Aymeric Aillet <aymeric.aillet@iot.bzh>,
Yusuke Goda <yusuke.goda.sx@renesas.com>
Subject: Re: [PATCH 4/4] drivers: clk: renesas: enable all clocks which is assinged to non Linux system
Date: Thu, 16 Nov 2023 13:23:24 -0600 [thread overview]
Message-ID: <20231116192324.GB2821275-robh@kernel.org> (raw)
In-Reply-To: <87wmulrynq.wl-kuninori.morimoto.gx@renesas.com>
On Tue, Nov 14, 2023 at 12:01:14AM +0000, Kuninori Morimoto wrote:
> Some board might use Linux and another OS in the same time. In such
> case, current Linux will stop necessary module clock when booting
> which is not used on Linux side, but is used on another OS side.
>
> To avoid such situation, renesas-cpg-mssr try to find
> status = "reserved" devices (A), and add CLK_IGNORE_UNUSED flag to its
> <&cgp CPG_MOD xxx> clock (B).
See Stephen's presentation from Plumbers this week. The default behavior
for unused clocks may be changing soon.
>
> Table 2.4: Values for status property
> https://github.com/devicetree-org/devicetree-specification/releases/download/v0.4/devicetree-specification-v0.4.pdf
>
> "reserved"
> Indicates that the device is operational, but should not be
> used. Typically this is used for devices that are controlled
> by another software component, such as platform firmware.
>
> ex)
> scif5: serial@e6f30000 {
> ...
> (B) clocks = <&cpg CPG_MOD 202>,
> <&cpg CPG_CORE R8A7795_CLK_S3D1>,
> <&scif_clk>;
> ...
> (A) status = "reserved";
> };
I have some reservations about whether a reserved node should be touched
at all by Linux. I suppose since it is platform specific, it's okay. I
don't think we could apply such behavior globally.
Rob
next prev parent reply other threads:[~2023-11-16 19:23 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-13 23:59 [PATCH 0/4] drivers: clk: renesas: enable all clocks which is assinged to non Linux system Kuninori Morimoto
2023-11-14 0:00 ` [PATCH 1/4] of: add __of_device_is_status() and makes more generic status check Kuninori Morimoto
2023-11-16 19:17 ` Rob Herring
2023-11-14 0:00 ` [PATCH 2/4] of: add __of_get_next_status_child() and makes more generic of_get_next Kuninori Morimoto
2023-11-14 0:01 ` [PATCH 3/4] of: add for_each_reserved_child_of_node() Kuninori Morimoto
2023-11-14 0:01 ` [PATCH 4/4] drivers: clk: renesas: enable all clocks which is assinged to non Linux system Kuninori Morimoto
2023-11-14 13:10 ` kernel test robot
2023-11-16 1:04 ` Kuninori Morimoto
2023-11-16 19:23 ` Rob Herring [this message]
2023-11-16 21:08 ` Geert Uytterhoeven
2023-11-27 21:32 ` Stephen Boyd
2023-11-27 23:48 ` Kuninori Morimoto
2023-12-01 22:39 ` Stephen Boyd
2023-12-04 0:26 ` Kuninori Morimoto
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