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![Alexandre Belloni](/assets/img/avatar_default.png)
The AT91 clock drivers make use of IRQs to avoid polling when waiting for some clocks to be enabled. Unfortunately, this leads to a crash when those IRQs are threaded (which happens when using preempt-rt) because they are registered before thread creation is possible. Use polling on those clocks instead to avoid the problem. Acked-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
131 lines
3 KiB
C
131 lines
3 KiB
C
/*
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* Copyright (C) 2013 Boris BREZILLON <b.brezillon@overkiz.com>
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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 as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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*/
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#include <linux/clk-provider.h>
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#include <linux/clkdev.h>
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#include <linux/clk/at91_pmc.h>
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#include <linux/of.h>
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#include <linux/mfd/syscon.h>
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#include <linux/regmap.h>
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#include "pmc.h"
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#define UTMI_FIXED_MUL 40
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struct clk_utmi {
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struct clk_hw hw;
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struct regmap *regmap;
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};
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#define to_clk_utmi(hw) container_of(hw, struct clk_utmi, hw)
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static inline bool clk_utmi_ready(struct regmap *regmap)
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{
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unsigned int status;
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regmap_read(regmap, AT91_PMC_SR, &status);
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return status & AT91_PMC_LOCKU;
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}
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static int clk_utmi_prepare(struct clk_hw *hw)
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{
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struct clk_utmi *utmi = to_clk_utmi(hw);
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unsigned int uckr = AT91_PMC_UPLLEN | AT91_PMC_UPLLCOUNT |
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AT91_PMC_BIASEN;
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regmap_update_bits(utmi->regmap, AT91_CKGR_UCKR, uckr, uckr);
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while (!clk_utmi_ready(utmi->regmap))
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cpu_relax();
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return 0;
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}
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static int clk_utmi_is_prepared(struct clk_hw *hw)
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{
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struct clk_utmi *utmi = to_clk_utmi(hw);
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return clk_utmi_ready(utmi->regmap);
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}
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static void clk_utmi_unprepare(struct clk_hw *hw)
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{
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struct clk_utmi *utmi = to_clk_utmi(hw);
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regmap_update_bits(utmi->regmap, AT91_CKGR_UCKR, AT91_PMC_UPLLEN, 0);
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}
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static unsigned long clk_utmi_recalc_rate(struct clk_hw *hw,
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unsigned long parent_rate)
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{
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/* UTMI clk is a fixed clk multiplier */
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return parent_rate * UTMI_FIXED_MUL;
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}
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static const struct clk_ops utmi_ops = {
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.prepare = clk_utmi_prepare,
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.unprepare = clk_utmi_unprepare,
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.is_prepared = clk_utmi_is_prepared,
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.recalc_rate = clk_utmi_recalc_rate,
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};
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static struct clk * __init
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at91_clk_register_utmi(struct regmap *regmap,
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const char *name, const char *parent_name)
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{
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struct clk_utmi *utmi;
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struct clk *clk = NULL;
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struct clk_init_data init;
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utmi = kzalloc(sizeof(*utmi), GFP_KERNEL);
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if (!utmi)
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return ERR_PTR(-ENOMEM);
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init.name = name;
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init.ops = &utmi_ops;
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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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init.flags = CLK_SET_RATE_GATE;
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utmi->hw.init = &init;
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utmi->regmap = regmap;
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clk = clk_register(NULL, &utmi->hw);
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if (IS_ERR(clk))
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kfree(utmi);
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return clk;
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}
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static void __init of_at91sam9x5_clk_utmi_setup(struct device_node *np)
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{
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struct clk *clk;
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const char *parent_name;
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const char *name = np->name;
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struct regmap *regmap;
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parent_name = of_clk_get_parent_name(np, 0);
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of_property_read_string(np, "clock-output-names", &name);
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regmap = syscon_node_to_regmap(of_get_parent(np));
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if (IS_ERR(regmap))
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return;
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clk = at91_clk_register_utmi(regmap, name, parent_name);
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if (IS_ERR(clk))
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return;
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of_clk_add_provider(np, of_clk_src_simple_get, clk);
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return;
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}
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CLK_OF_DECLARE(at91sam9x5_clk_utmi, "atmel,at91sam9x5-clk-utmi",
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of_at91sam9x5_clk_utmi_setup);
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