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From:   Samuel Holland <samuel@sholland.org>
To:     Jassi Brar <jassisinghbrar@gmail.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>
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: [PATCH v2 02/10] clk: sunxi-ng: sun9i: Mark the msgbox clock as critical
Date:   Thu, 28 Feb 2019 23:29:39 -0600
Message-Id: <20190301052947.32032-3-samuel@sholland.org>
In-Reply-To: <20190301052947.32032-1-samuel@sholland.org>
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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 does not exist for the A80.
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 this SoC.

Signed-off-by: Samuel Holland <samuel@sholland.org>
---
 drivers/clk/sunxi-ng/ccu-sun9i-a80.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/sunxi-ng/ccu-sun9i-a80.c b/drivers/clk/sunxi-ng/ccu-sun9i-a80.c
index 8936ef87652c..f9309782e7d8 100644
--- a/drivers/clk/sunxi-ng/ccu-sun9i-a80.c
+++ b/drivers/clk/sunxi-ng/ccu-sun9i-a80.c
@@ -756,7 +756,7 @@ static SUNXI_CCU_GATE(bus_usb_clk,	"bus-usb",	"ahb1",
 static SUNXI_CCU_GATE(bus_gmac_clk,	"bus-gmac",	"ahb1",
 		      0x584, BIT(17), 0);
 static SUNXI_CCU_GATE(bus_msgbox_clk,	"bus-msgbox",	"ahb1",
-		      0x584, BIT(21), 0);
+		      0x584, BIT(21), CLK_IS_CRITICAL);
 static SUNXI_CCU_GATE(bus_spinlock_clk,	"bus-spinlock",	"ahb1",
 		      0x584, BIT(22), 0);
 static SUNXI_CCU_GATE(bus_hstimer_clk,	"bus-hstimer",	"ahb1",
-- 
2.19.2