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From:   Samuel Holland <samuel@sholland.org>
To:     Maxime Ripard <maxime.ripard@bootlin.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Corentin Labbe <clabbe.montjoie@gmail.com>,
        Vasily Khoruzhick <anarsoul@gmail.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 v4 02/10] clk: sunxi-ng: Mark AR100 clocks as critical
Date:   Mon, 19 Aug 2019 22:23:03 -0500
Message-Id: <20190820032311.6506-3-samuel@sholland.org>
In-Reply-To: <20190820032311.6506-1-samuel@sholland.org>
References: <20190820032311.6506-1-samuel@sholland.org>
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On sun8i, sun9i, and sun50i SoCs, system suspend/resume support requires
firmware running on the AR100 coprocessor (the "SCP"). Such firmware can
provide additional features, such as thermal monitoring and poweron/off
support for boards without a PMIC.

Since the AR100 may be running critical firmware, even if Linux does not
know about it or directly interact with it (all requests may go through
an intermediary interface such as PSCI), Linux must not turn off its
clock.

At this time, such power management firmware only exists for the A64 and
H5 SoCs.  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.

Leaving the clock running is safe even if no firmware is present, since
the AR100 stays in reset by default. In most cases, the AR100 clock is
kept enabled by Linux anyway, since it is the parent of all APB0 bus
peripherals. This change only prevents Linux from turning off the AR100
clock in the rare case that no peripherals are in use.

Signed-off-by: Samuel Holland <samuel@sholland.org>
---
 drivers/clk/sunxi-ng/ccu-sun50i-h6-r.c | 2 +-
 drivers/clk/sunxi-ng/ccu-sun8i-r.c     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-h6-r.c b/drivers/clk/sunxi-ng/ccu-sun50i-h6-r.c
index 45a1ed3fe674..adf907020951 100644
--- a/drivers/clk/sunxi-ng/ccu-sun50i-h6-r.c
+++ b/drivers/clk/sunxi-ng/ccu-sun50i-h6-r.c
@@ -45,7 +45,7 @@ static struct ccu_div ar100_clk = {
 		.hw.init	= CLK_HW_INIT_PARENTS("ar100",
 						      ar100_r_apb2_parents,
 						      &ccu_div_ops,
-						      0),
+						      CLK_IS_CRITICAL),
 	},
 };
 
diff --git a/drivers/clk/sunxi-ng/ccu-sun8i-r.c b/drivers/clk/sunxi-ng/ccu-sun8i-r.c
index 4646fdc61053..feef4f750943 100644
--- a/drivers/clk/sunxi-ng/ccu-sun8i-r.c
+++ b/drivers/clk/sunxi-ng/ccu-sun8i-r.c
@@ -45,7 +45,7 @@ static struct ccu_div ar100_clk = {
 		.hw.init	= CLK_HW_INIT_PARENTS_DATA("ar100",
 							   ar100_parents,
 							   &ccu_div_ops,
-							   0),
+							   CLK_IS_CRITICAL),
 	},
 };
 
-- 
2.21.0