linux-kernel - [PATCH 1/4] clk: sprd: check its parent status before reading gate clock

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Date:   Mon, 30 Mar 2020 15:14:48 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang7@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Chunyan Zhang <chunyan.zhang@...soc.com>
Subject: [PATCH 1/4] clk: sprd: check its parent status before reading gate clock

From: Chunyan Zhang <chunyan.zhang@...soc.com>

Some clocks only can be accessed if their parent is enabled. mipi_csi_xx
clocks on SC9863A are examples. We have to ensure the parent clock is
enabled when reading those clocks.

Signed-off-by: Chunyan Zhang <chunyan.zhang@...soc.com>
---
 drivers/clk/sprd/gate.c | 8 ++++++++
 drivers/clk/sprd/gate.h | 9 +++++++++
 2 files changed, 17 insertions(+)

diff --git a/drivers/clk/sprd/gate.c b/drivers/clk/sprd/gate.c
index 574cfc116bbc..8d14073b9cb8 100644
--- a/drivers/clk/sprd/gate.c
+++ b/drivers/clk/sprd/gate.c
@@ -5,6 +5,7 @@
 // Copyright (C) 2017 Spreadtrum, Inc.
 // Author: Chunyan Zhang <chunyan.zhang@...eadtrum.com>
 
+#include <linux/clk.h>
 #include <linux/clk-provider.h>
 #include <linux/regmap.h>
 
@@ -94,8 +95,15 @@ static int sprd_gate_is_enabled(struct clk_hw *hw)
 {
 	struct sprd_gate *sg = hw_to_sprd_gate(hw);
 	struct sprd_clk_common *common = &sg->common;
+	struct clk_hw *parent;
 	unsigned int reg;
 
+	if (sg->flags & SPRD_GATE_NON_AON) {
+		parent = clk_hw_get_parent(hw);
+		if (!parent || !clk_hw_is_enabled(parent))
+			return 0;
+	}
+
 	regmap_read(common->regmap, common->reg, &reg);
 
 	if (sg->flags & CLK_GATE_SET_TO_DISABLE)
diff --git a/drivers/clk/sprd/gate.h b/drivers/clk/sprd/gate.h
index b55817869367..aa4d72381788 100644
--- a/drivers/clk/sprd/gate.h
+++ b/drivers/clk/sprd/gate.h
@@ -19,6 +19,15 @@ struct sprd_gate {
 	struct sprd_clk_common	common;
 };
 
+/*
+ * sprd_gate->flags is used for:
+ * CLK_GATE_SET_TO_DISABLE	BIT(0)
+ * CLK_GATE_HIWORD_MASK		BIT(1)
+ * CLK_GATE_BIG_ENDIAN		BIT(2)
+ * so we define new flags from	BIT(3)
+ */
+#define SPRD_GATE_NON_AON BIT(3) /* not alway on, need to check before read */
+
 #define SPRD_SC_GATE_CLK_HW_INIT_FN(_struct, _name, _parent, _reg,	\
 				    _sc_offset, _enable_mask, _flags,	\
 				    _gate_flags, _udelay, _ops, _fn)	\
-- 
2.20.1