From: Stephen Boyd <sboyd@kernel.org>
To: Chen-Yu Tsai <wens@csie.org>,
Jassi Brar <jassisinghbrar@gmail.com>,
Mark Rutland <mark.rutland@arm.com>,
Maxime Ripard <maxime.ripard@bootlin.com>,
Michael Turquette <mturquette@baylibre.com>,
Rob Herring <robh+dt@kernel.org>,
Samuel Holland <samuel@sholland.org>
Cc: devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-sunxi@googlegroups.com,
Samuel Holland <samuel@sholland.org>
Subject: Re: [PATCH v2 03/10] clk: sunxi-ng: sun50i: Mark the msgbox clock as critical
Date: Fri, 01 Mar 2019 09:31:23 -0800 [thread overview]
Message-ID: <155146148359.16805.78863244252924530@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <20190301052947.32032-4-samuel@sholland.org>
Quoting Samuel Holland (2019-02-28 21:29:40)
> The msgbox clock is critical because the hardware is shared between
> Linux and system firmware. The message box may be used by the EL3 secure
> monitor's PSCI implementation. On 64-bit sunxi SoCs, this is provided by
> ARM TF-A; 32-bit SoCs use a different implementation. The secure monitor
> uses the message box to forward requests to power management firmware
> running on a separate CPU.
>
> It is not enough for the secure monitor to enable the clock each time
> Linux performs a SMC into EL3, as both the firmware and Linux can run
> concurrently on separate CPUs. So it is never safe for Linux to turn
> this clock off, and it should be marked as critical.
>
> At this time, such power management firmware only exists for the A64.
> However, it makes sense to take care of all CCU drivers now for
> consistency, and to ease the transition in the future, once firmware is
> ported to the other SoCs.
>
> Signed-off-by: Samuel Holland <samuel@sholland.org>
> ---
> drivers/clk/sunxi-ng/ccu-sun50i-a64.c | 2 +-
> drivers/clk/sunxi-ng/ccu-sun50i-h6.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
> index 932836d26e2b..7780e855c56f 100644
> --- a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
> +++ b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
> @@ -350,7 +350,7 @@ static SUNXI_CCU_GATE(bus_de_clk, "bus-de", "ahb1",
> static SUNXI_CCU_GATE(bus_gpu_clk, "bus-gpu", "ahb1",
> 0x064, BIT(20), 0);
> static SUNXI_CCU_GATE(bus_msgbox_clk, "bus-msgbox", "ahb1",
> - 0x064, BIT(21), 0);
> + 0x064, BIT(21), CLK_IS_CRITICAL);
Please add a comment explaining why CLK_IS_CRITICAL is used. It helps us
remember years from now without having to dig in the git history.
next prev parent reply other threads:[~2019-03-01 17:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-01 5:29 [PATCH v2 00/10] Allwinner sunxi message box support Samuel Holland
2019-03-01 5:29 ` [PATCH v2 01/10] clk: sunxi-ng: sun8i: Mark the msgbox clock as critical Samuel Holland
2019-03-01 5:29 ` [PATCH v2 02/10] clk: sunxi-ng: sun9i: " Samuel Holland
2019-03-01 5:29 ` [PATCH v2 03/10] clk: sunxi-ng: sun50i: " Samuel Holland
2019-03-01 17:31 ` Stephen Boyd [this message]
2019-03-01 5:29 ` [PATCH v2 04/10] dt-bindings: mailbox: Add a sunxi message box binding Samuel Holland
2019-03-01 5:29 ` [PATCH v2 05/10] mailbox: sunxi-msgbox: Add a new mailbox driver Samuel Holland
2019-03-01 5:29 ` [PATCH v2 06/10] ARM: dts: sunxi: a80: Add msgbox node Samuel Holland
2019-03-01 5:29 ` [PATCH v2 07/10] ARM: dts: sunxi: a83t: " Samuel Holland
2019-03-01 5:29 ` [PATCH v2 08/10] ARM: dts: sunxi: h3/h5: " Samuel Holland
2019-03-01 5:29 ` [PATCH v2 09/10] arm64: dts: allwinner: a64: " Samuel Holland
2019-03-01 5:29 ` [PATCH v2 10/10] arm64: dts: allwinner: h6: " Samuel Holland
2019-03-01 5:53 ` [linux-sunxi] [PATCH v2 00/10] Allwinner sunxi message box support Corentin Labbe
2019-03-01 14:47 ` Maxime Ripard
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