63288b721a
Let's say clock A and B are two gate clocks that share the same register
bit in hardware. Therefore they are registered as shared gate clocks
with imx_clk_gate2_shared().
In a scenario that only clock A is enabled by clk_enable(A) while B is
not used, the shared gate will be unexpectedly disabled in hardware.
It happens because clk_enable(A) increments the share_count from 0 to 1,
while clock B is unused to clock core, and therefore the core function
will just disable B by calling clk->ops->disable() directly. The
consequence of that call is share_count is decremented to 0 and the gate
is disabled in hardware, even though clock A is still in use.
The patch fixes the issue by initializing the share_count per hardware
state and returns enable state per share_count from .is_enabled() hook,
in case it's a shared gate.
While at it, add a check in clk_gate2_disable() to ensure it's never
called with a zero share_count.
Reported-by: Fabio Estevam <fabio.estevam@freescale.com>
Fixes: f9f28cdf21 ("ARM: imx: add shared gate clock support")
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
149 lines
3.3 KiB
C
149 lines
3.3 KiB
C
/*
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* Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr@canonical.com>
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* Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Gated clock implementation
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*/
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#include <linux/clk-provider.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/io.h>
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#include <linux/err.h>
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#include <linux/string.h>
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#include "clk.h"
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/**
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* DOC: basic gatable clock which can gate and ungate it's ouput
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*
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* Traits of this clock:
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* prepare - clk_(un)prepare only ensures parent is (un)prepared
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* enable - clk_enable and clk_disable are functional & control gating
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* rate - inherits rate from parent. No clk_set_rate support
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* parent - fixed parent. No clk_set_parent support
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*/
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struct clk_gate2 {
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struct clk_hw hw;
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void __iomem *reg;
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u8 bit_idx;
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u8 flags;
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spinlock_t *lock;
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unsigned int *share_count;
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};
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#define to_clk_gate2(_hw) container_of(_hw, struct clk_gate2, hw)
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static int clk_gate2_enable(struct clk_hw *hw)
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{
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struct clk_gate2 *gate = to_clk_gate2(hw);
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u32 reg;
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unsigned long flags = 0;
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spin_lock_irqsave(gate->lock, flags);
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if (gate->share_count && (*gate->share_count)++ > 0)
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goto out;
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reg = readl(gate->reg);
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reg |= 3 << gate->bit_idx;
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writel(reg, gate->reg);
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out:
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spin_unlock_irqrestore(gate->lock, flags);
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return 0;
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}
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static void clk_gate2_disable(struct clk_hw *hw)
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{
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struct clk_gate2 *gate = to_clk_gate2(hw);
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u32 reg;
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unsigned long flags = 0;
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spin_lock_irqsave(gate->lock, flags);
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if (gate->share_count) {
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if (WARN_ON(*gate->share_count == 0))
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goto out;
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else if (--(*gate->share_count) > 0)
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goto out;
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}
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reg = readl(gate->reg);
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reg &= ~(3 << gate->bit_idx);
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writel(reg, gate->reg);
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out:
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spin_unlock_irqrestore(gate->lock, flags);
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}
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static int clk_gate2_reg_is_enabled(void __iomem *reg, u8 bit_idx)
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{
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u32 val = readl(reg);
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if (((val >> bit_idx) & 1) == 1)
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return 1;
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return 0;
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}
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static int clk_gate2_is_enabled(struct clk_hw *hw)
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{
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struct clk_gate2 *gate = to_clk_gate2(hw);
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if (gate->share_count)
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return !!(*gate->share_count);
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else
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return clk_gate2_reg_is_enabled(gate->reg, gate->bit_idx);
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}
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static struct clk_ops clk_gate2_ops = {
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.enable = clk_gate2_enable,
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.disable = clk_gate2_disable,
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.is_enabled = clk_gate2_is_enabled,
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};
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struct clk *clk_register_gate2(struct device *dev, const char *name,
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const char *parent_name, unsigned long flags,
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void __iomem *reg, u8 bit_idx,
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u8 clk_gate2_flags, spinlock_t *lock,
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unsigned int *share_count)
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{
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struct clk_gate2 *gate;
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struct clk *clk;
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struct clk_init_data init;
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gate = kzalloc(sizeof(struct clk_gate2), GFP_KERNEL);
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if (!gate)
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return ERR_PTR(-ENOMEM);
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/* struct clk_gate2 assignments */
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gate->reg = reg;
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gate->bit_idx = bit_idx;
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gate->flags = clk_gate2_flags;
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gate->lock = lock;
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/* Initialize share_count per hardware state */
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if (share_count)
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*share_count = clk_gate2_reg_is_enabled(reg, bit_idx) ? 1 : 0;
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gate->share_count = share_count;
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init.name = name;
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init.ops = &clk_gate2_ops;
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init.flags = flags;
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init.parent_names = parent_name ? &parent_name : NULL;
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init.num_parents = parent_name ? 1 : 0;
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gate->hw.init = &init;
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clk = clk_register(dev, &gate->hw);
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if (IS_ERR(clk))
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kfree(gate);
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return clk;
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}
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