linux-stable/drivers/clk/tegra/clk-periph.c
Dmitry Osipenko c592c8a28f clk: tegra: Fix refcounting of gate clocks
The refcounting of the gate clocks has a bug causing the enable_refcnt
to underflow when unused clocks are disabled. This happens because clk
provider erroneously bumps the refcount if clock is enabled at a boot
time, which it shouldn't be doing, and it does this only for the gate
clocks, while peripheral clocks are using the same gate ops and the
peripheral clocks are missing the initial bump. Hence the refcount of
the peripheral clocks is 0 when unused clocks are disabled and then the
counter is decremented further by the gate ops, causing the integer
underflow.

Fix this problem by removing the erroneous bump and by implementing the
disable_unused() callback, which disables the unused gates properly.

The visible effect of the bug is such that the unused clocks are never
gated if a loaded kernel module grabs the unused clocks and starts to use
them. In practice this shouldn't cause any real problems for the drivers
and boards supported by the kernel today.

Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
2021-05-31 15:16:24 +02:00

234 lines
6.5 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2012, NVIDIA CORPORATION. All rights reserved.
*/
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include "clk.h"
static u8 clk_periph_get_parent(struct clk_hw *hw)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *mux_ops = periph->mux_ops;
struct clk_hw *mux_hw = &periph->mux.hw;
__clk_hw_set_clk(mux_hw, hw);
return mux_ops->get_parent(mux_hw);
}
static int clk_periph_set_parent(struct clk_hw *hw, u8 index)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *mux_ops = periph->mux_ops;
struct clk_hw *mux_hw = &periph->mux.hw;
__clk_hw_set_clk(mux_hw, hw);
return mux_ops->set_parent(mux_hw, index);
}
static unsigned long clk_periph_recalc_rate(struct clk_hw *hw,
unsigned long parent_rate)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *div_ops = periph->div_ops;
struct clk_hw *div_hw = &periph->divider.hw;
__clk_hw_set_clk(div_hw, hw);
return div_ops->recalc_rate(div_hw, parent_rate);
}
static long clk_periph_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *prate)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *div_ops = periph->div_ops;
struct clk_hw *div_hw = &periph->divider.hw;
__clk_hw_set_clk(div_hw, hw);
return div_ops->round_rate(div_hw, rate, prate);
}
static int clk_periph_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *div_ops = periph->div_ops;
struct clk_hw *div_hw = &periph->divider.hw;
__clk_hw_set_clk(div_hw, hw);
return div_ops->set_rate(div_hw, rate, parent_rate);
}
static int clk_periph_is_enabled(struct clk_hw *hw)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *gate_ops = periph->gate_ops;
struct clk_hw *gate_hw = &periph->gate.hw;
__clk_hw_set_clk(gate_hw, hw);
return gate_ops->is_enabled(gate_hw);
}
static int clk_periph_enable(struct clk_hw *hw)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *gate_ops = periph->gate_ops;
struct clk_hw *gate_hw = &periph->gate.hw;
__clk_hw_set_clk(gate_hw, hw);
return gate_ops->enable(gate_hw);
}
static void clk_periph_disable(struct clk_hw *hw)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *gate_ops = periph->gate_ops;
struct clk_hw *gate_hw = &periph->gate.hw;
gate_ops->disable(gate_hw);
}
static void clk_periph_disable_unused(struct clk_hw *hw)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *gate_ops = periph->gate_ops;
struct clk_hw *gate_hw = &periph->gate.hw;
gate_ops->disable_unused(gate_hw);
}
static void clk_periph_restore_context(struct clk_hw *hw)
{
struct tegra_clk_periph *periph = to_clk_periph(hw);
const struct clk_ops *div_ops = periph->div_ops;
struct clk_hw *div_hw = &periph->divider.hw;
int parent_id;
parent_id = clk_hw_get_parent_index(hw);
if (WARN_ON(parent_id < 0))
return;
if (!(periph->gate.flags & TEGRA_PERIPH_NO_DIV))
div_ops->restore_context(div_hw);
clk_periph_set_parent(hw, parent_id);
}
const struct clk_ops tegra_clk_periph_ops = {
.get_parent = clk_periph_get_parent,
.set_parent = clk_periph_set_parent,
.recalc_rate = clk_periph_recalc_rate,
.round_rate = clk_periph_round_rate,
.set_rate = clk_periph_set_rate,
.is_enabled = clk_periph_is_enabled,
.enable = clk_periph_enable,
.disable = clk_periph_disable,
.disable_unused = clk_periph_disable_unused,
.restore_context = clk_periph_restore_context,
};
static const struct clk_ops tegra_clk_periph_nodiv_ops = {
.get_parent = clk_periph_get_parent,
.set_parent = clk_periph_set_parent,
.is_enabled = clk_periph_is_enabled,
.enable = clk_periph_enable,
.disable = clk_periph_disable,
.disable_unused = clk_periph_disable_unused,
.restore_context = clk_periph_restore_context,
};
static const struct clk_ops tegra_clk_periph_no_gate_ops = {
.get_parent = clk_periph_get_parent,
.set_parent = clk_periph_set_parent,
.recalc_rate = clk_periph_recalc_rate,
.round_rate = clk_periph_round_rate,
.set_rate = clk_periph_set_rate,
.restore_context = clk_periph_restore_context,
};
static struct clk *_tegra_clk_register_periph(const char *name,
const char * const *parent_names, int num_parents,
struct tegra_clk_periph *periph,
void __iomem *clk_base, u32 offset,
unsigned long flags)
{
struct clk *clk;
struct clk_init_data init;
const struct tegra_clk_periph_regs *bank;
bool div = !(periph->gate.flags & TEGRA_PERIPH_NO_DIV);
if (periph->gate.flags & TEGRA_PERIPH_NO_DIV) {
flags |= CLK_SET_RATE_PARENT;
init.ops = &tegra_clk_periph_nodiv_ops;
} else if (periph->gate.flags & TEGRA_PERIPH_NO_GATE)
init.ops = &tegra_clk_periph_no_gate_ops;
else
init.ops = &tegra_clk_periph_ops;
init.name = name;
init.flags = flags;
init.parent_names = parent_names;
init.num_parents = num_parents;
bank = get_reg_bank(periph->gate.clk_num);
if (!bank)
return ERR_PTR(-EINVAL);
/* Data in .init is copied by clk_register(), so stack variable OK */
periph->hw.init = &init;
periph->magic = TEGRA_CLK_PERIPH_MAGIC;
periph->mux.reg = clk_base + offset;
periph->divider.reg = div ? (clk_base + offset) : NULL;
periph->gate.clk_base = clk_base;
periph->gate.regs = bank;
periph->gate.enable_refcnt = periph_clk_enb_refcnt;
clk = clk_register(NULL, &periph->hw);
if (IS_ERR(clk))
return clk;
periph->mux.hw.clk = clk;
periph->divider.hw.clk = div ? clk : NULL;
periph->gate.hw.clk = clk;
return clk;
}
struct clk *tegra_clk_register_periph(const char *name,
const char * const *parent_names, int num_parents,
struct tegra_clk_periph *periph, void __iomem *clk_base,
u32 offset, unsigned long flags)
{
return _tegra_clk_register_periph(name, parent_names, num_parents,
periph, clk_base, offset, flags);
}
struct clk *tegra_clk_register_periph_nodiv(const char *name,
const char * const *parent_names, int num_parents,
struct tegra_clk_periph *periph, void __iomem *clk_base,
u32 offset)
{
periph->gate.flags |= TEGRA_PERIPH_NO_DIV;
return _tegra_clk_register_periph(name, parent_names, num_parents,
periph, clk_base, offset, CLK_SET_RATE_PARENT);
}
struct clk *tegra_clk_register_periph_data(void __iomem *clk_base,
struct tegra_periph_init_data *init)
{
return _tegra_clk_register_periph(init->name, init->p.parent_names,
init->num_parents, &init->periph,
clk_base, init->offset, init->flags);
}