Re: [PATCH v1 01/11] clk: mediatek: add new clkmux register API

Weiyi Lu
2018-11-20T06:35:10Z

On Tue, 2018-11-13 at 08:00 -0800, Nicolas Boichat wrote:
> On Mon, Nov 5, 2018 at 10:42 PM Weiyi Lu <weiyi.lu@mediatek.com> wrote:
> >
> > From: Owen Chen <owen.chen@mediatek.com>
> >
> > On both MT8183 & MT6765, there add "set/clr" register for
> > each clkmux setting, and one update register to trigger value change.
> > It is designed to prevent read-modify-write racing issue.
> > The sw design need to add a new API to handle this hw change with
> > a new mtk_clk_mux/mtk_mux struct in new file "clk-mux.c", "clk-mux.h".
> >
> > Signed-off-by: Owen Chen <owen.chen@mediatek.com>
> > Signed-off-by: Weiyi Lu <weiyi.lu@mediatek.com>
> > ---
> > drivers/clk/mediatek/Makefile | 2 +-
> > drivers/clk/mediatek/clk-mux.c | 252 +++++++++++++++++++++++++++++++++
> > drivers/clk/mediatek/clk-mux.h | 101 +++++++++++++
> > 3 files changed, 354 insertions(+), 1 deletion(-)
> > create mode 100644 drivers/clk/mediatek/clk-mux.c
> > create mode 100644 drivers/clk/mediatek/clk-mux.h
> >
> > diff --git a/drivers/clk/mediatek/Makefile b/drivers/clk/mediatek/Makefile
> > index 844b55d2770d..b97980dbb738 100644
> > --- a/drivers/clk/mediatek/Makefile
> > +++ b/drivers/clk/mediatek/Makefile
> > @@ -1,5 +1,5 @@
> > # SPDX-License-Identifier: GPL-2.0
> > -obj-$(CONFIG_COMMON_CLK_MEDIATEK) += clk-mtk.o clk-pll.o clk-gate.o clk-apmixed.o clk-cpumux.o reset.o
> > +obj-$(CONFIG_COMMON_CLK_MEDIATEK) += clk-mtk.o clk-pll.o clk-gate.o clk-apmixed.o clk-cpumux.o reset.o clk-mux.o
> > obj-$(CONFIG_COMMON_CLK_MT6797) += clk-mt6797.o
> > obj-$(CONFIG_COMMON_CLK_MT6797_IMGSYS) += clk-mt6797-img.o
> > obj-$(CONFIG_COMMON_CLK_MT6797_MMSYS) += clk-mt6797-mm.o
> > diff --git a/drivers/clk/mediatek/clk-mux.c b/drivers/clk/mediatek/clk-mux.c
> > new file mode 100644
> > index 000000000000..18bc9a146be0
> > --- /dev/null
> > +++ b/drivers/clk/mediatek/clk-mux.c
> > @@ -0,0 +1,252 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2018 MediaTek Inc.
> > + * Author: Owen Chen <owen.chen@mediatek.com>
> > + */
> > +
> > +#include <linux/of.h>
> > +#include <linux/of_address.h>
> > +#include <linux/slab.h>
> > +#include <linux/mfd/syscon.h>
> > +
> > +#include "clk-mtk.h"
> > +#include "clk-mux.h"
> > +
> > +static inline struct mtk_clk_mux
> > + *to_mtk_clk_mux(struct clk_hw *hw)
> > +{
> > + return container_of(hw, struct mtk_clk_mux, hw);
> > +}
> > +
> > +static int mtk_clk_mux_enable(struct clk_hw *hw)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + u32 mask = BIT(mux->gate_shift);
> > +
> > + regmap_update_bits(mux->regmap, mux->mux_ofs, mask, 0);
> > +
> > + return 0;
>
> Might as well return regmap_update_bits(...).
>

OK, will fix in next version

> > +}
> > +
> > +static void mtk_clk_mux_disable(struct clk_hw *hw)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + u32 mask = BIT(mux->gate_shift);
> > +
> > + regmap_update_bits(mux->regmap, mux->mux_ofs, mask, mask);
> > +}
> > +
> > +static int mtk_clk_mux_enable_setclr(struct clk_hw *hw)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + u32 val;
> > +
> > + val = BIT(mux->gate_shift);
> > + regmap_write(mux->regmap, mux->mux_clr_ofs, val);
> > +
> > + return 0;
>
> ditto: return regmap_write(...) .
>

will fix in next version

> > +}
> > +
> > +static void mtk_clk_mux_disable_setclr(struct clk_hw *hw)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + u32 val;
> > +
> > + val = BIT(mux->gate_shift);
> > + regmap_write(mux->regmap, mux->mux_set_ofs, val);
> > +}
> > +
> > +static int mtk_clk_mux_is_enabled(struct clk_hw *hw)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + u32 val = 0;
>
> No need to init to 0.
>

will fix in next version

> > +
> > + regmap_read(mux->regmap, mux->mux_ofs, &val);
> > +
> > + return ((val & BIT(mux->gate_shift)) == 0) ? 1 : 0;
>
> Just (val & BIT(mux->gate_shift)) != 0. Or more simply val &
> BIT(mux->gate_shift).
>

will fix in next version

> > +}
> > +
> > +static u8 mtk_clk_mux_get_parent(struct clk_hw *hw)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + int num_parents = clk_hw_get_num_parents(hw);
> > + u32 mask = GENMASK(mux->mux_width - 1, 0);
> > + u32 val;
> > +
> > + regmap_read(mux->regmap, mux->mux_ofs, &val);
> > + val = (val >> mux->mux_shift) & mask;
> > +
> > + if (val >= num_parents || val >= U8_MAX)
>
> val > U8_MAX, technically.
>
> > + return -ERANGE;
>
> This looks wrong, -34 will be cast to an u8 and appear to be valid...
>

will fix in next version

> > +
> > + return val;
> > +}
> > +
> > +static int mtk_clk_mux_set_parent_lock(struct clk_hw *hw, u8 index)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + u32 mask = GENMASK(mux->mux_width - 1, 0);
> > + u32 val;
> > + unsigned long flags = 0;
>
> No need to init to 0.
>

will fix in next version.

> > +
> > + if (mux->lock)
> > + spin_lock_irqsave(mux->lock, flags);
> > + else
> > + __acquire(mux->lock);
> > +
> > + regmap_read(mux->regmap, mux->mux_ofs, &val);
> > + val = (val & mask) >> mux->mux_shift;
> > +
> > + if (val != index) {
> > + val = index << mux->mux_shift;
> > + regmap_update_bits(mux->regmap, mux->mux_ofs, mask, val);
> > + }
>
> What's the point of doing read/compare/update? Are there side effects
> if you just write the value unconditionally?
>

Actually writing the value directly has no side effects. We just want to
reduce unnecessary operations if the target parent of mux is already
selected.

> > +
> > + if (mux->lock)
> > + spin_unlock_irqrestore(mux->lock, flags);
> > + else
> > + __release(mux->lock);
> > +
> > + return 0;
> > +}
> > +
> > +static int mtk_clk_mux_set_parent_setclr_lock(struct clk_hw *hw, u8 index)
> > +{
> > + struct mtk_clk_mux *mux = to_mtk_clk_mux(hw);
> > + u32 mask = GENMASK(mux->mux_width - 1, 0);
> > + u32 val, orig;
> > + unsigned long flags = 0;
> > +
> > + if (mux->lock)
> > + spin_lock_irqsave(mux->lock, flags);
> > + else
> > + __acquire(mux->lock);
> > +
> > + regmap_read(mux->regmap, mux->mux_ofs, &val);
> > + orig = val;
>
> Just read into &orig above.
>

will fix in next version

> > + val &= ~(mask << mux->mux_shift);
> > + val |= index << mux->mux_shift;
>
> Maybe this is more readable?
> val = orig & ~(mask << mux->mux_shift) | (index << mux->mux_shift)
>

will fix in next version

> > +
> > + if (val != orig) {
> > + val = (mask << mux->mux_shift);
> > + regmap_write(mux->regmap, mux->mux_clr_ofs, val);
>
> I'd just regmap_write(..., mask << mux->mux_shift), instead if overriding val.
>

will fix in next version

> > + val = (index << mux->mux_shift);
> > + regmap_write(mux->regmap, mux->mux_set_ofs, val);
> > +
> > + if (mux->upd_shift >= 0)
> > + regmap_write(mux->regmap, mux->upd_ofs,
> > + BIT(mux->upd_shift));
> > + }
> > +
> > + if (mux->lock)
> > + spin_unlock_irqrestore(mux->lock, flags);
> > + else
> > + __release(mux->lock);
> > +
> > + return 0;
> > +}
> > +
> > +const struct clk_ops mtk_mux_ops = {
> > + .get_parent = mtk_clk_mux_get_parent,
> > + .set_parent = mtk_clk_mux_set_parent_lock,
> > +};
> > +
> > +const struct clk_ops mtk_mux_clr_set_upd_ops = {
> > + .get_parent = mtk_clk_mux_get_parent,
> > + .set_parent = mtk_clk_mux_set_parent_setclr_lock,
> > +};
> > +
> > +const struct clk_ops mtk_mux_gate_ops = {
> > + .enable = mtk_clk_mux_enable,
> > + .disable = mtk_clk_mux_disable,
> > + .is_enabled = mtk_clk_mux_is_enabled,
> > + .get_parent = mtk_clk_mux_get_parent,
> > + .set_parent = mtk_clk_mux_set_parent_lock,
> > +};
> > +
> > +const struct clk_ops mtk_mux_gate_clr_set_upd_ops = {
> > + .enable = mtk_clk_mux_enable_setclr,
> > + .disable = mtk_clk_mux_disable_setclr,
> > + .is_enabled = mtk_clk_mux_is_enabled,
> > + .get_parent = mtk_clk_mux_get_parent,
> > + .set_parent = mtk_clk_mux_set_parent_setclr_lock,
> > +};
> > +
> > +struct clk *mtk_clk_register_mux(const struct mtk_mux *mux,
> > + struct regmap *regmap,
> > + spinlock_t *lock)
> > +{
> > + struct mtk_clk_mux *mtk_mux = NULL;
>
> Not necessary to init to NULL.
>

will fix in next version

> > + struct clk_init_data init;
> > + struct clk *clk;
> > +
> > + mtk_mux = kzalloc(sizeof(*mtk_mux), GFP_KERNEL);
> > + if (!mtk_mux)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + init.name = mux->name;
> > + init.flags = (mux->flags) | CLK_SET_RATE_PARENT;
>
> mux->flags | CLK_SET_RATE_PARENT
>

will fix in next version

> > + init.parent_names = mux->parent_names;
> > + init.num_parents = mux->num_parents;
> > + init.ops = mux->ops;
> > +
> > + mtk_mux->regmap = regmap;
> > + mtk_mux->name = mux->name;
> > + mtk_mux->mux_ofs = mux->mux_ofs;
> > + mtk_mux->mux_set_ofs = mux->set_ofs;
> > + mtk_mux->mux_clr_ofs = mux->clr_ofs;
> > + mtk_mux->upd_ofs = mux->upd_ofs;
> > + mtk_mux->mux_shift = mux->mux_shift;
> > + mtk_mux->mux_width = mux->mux_width;
> > + mtk_mux->gate_shift = mux->gate_shift;
> > + mtk_mux->upd_shift = mux->upd_shift;
> > +
> > + mtk_mux->lock = lock;
> > + mtk_mux->hw.init = &init;
> > +
> > + clk = clk_register(NULL, &mtk_mux->hw);
> > + if (IS_ERR(clk)) {
> > + kfree(mtk_mux);
> > + return clk;
> > + }
> > +
> > + return clk;
> > +}
> > +
> > +int mtk_clk_register_muxes(const struct mtk_mux *muxes,
> > + int num, struct device_node *node,
> > + spinlock_t *lock,
> > + struct clk_onecell_data *clk_data)
> > +{
> > + struct regmap *regmap;
> > + struct clk *clk;
> > + int i;
> > +
> > + if (!clk_data)
> > + return -ENOMEM;
>
> Is this check necessary? After all you know who the callers are and
> maybe you need to be careful not to call this with NULL clk_data?
>

You're right. it's unnecessary. will fix in next version

> > +
> > + regmap = syscon_node_to_regmap(node);
> > + if (IS_ERR(regmap)) {
> > + pr_err("Cannot find regmap for %pOF: %ld\n", node,
> > + PTR_ERR(regmap));
> > + return PTR_ERR(regmap);
> > + }
> > +
> > + for (i = 0; i < num; i++) {
> > + const struct mtk_mux *mux = &muxes[i];
> > +
> > + if (IS_ERR_OR_NULL(clk_data->clks[mux->id])) {
>
> A NULL check seems enough, as you'll never assign a PTR_ERR(..) value
> into clk_data->clks[mux->id].
>
> > + clk = mtk_clk_register_mux(mux, regmap, lock);
> > +
> > + if (IS_ERR(clk)) {
> > + pr_err("Failed to register clk %s: %ld\n",
> > + mux->name, PTR_ERR(clk));
> > + continue;
>
> Are we ok with returning 0 even though some of these calls failed?
>

We'd like to skip the failed one first and keep registering the
remainings.

> > + }
> > +
> > + clk_data->clks[mux->id] = clk;
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > diff --git a/drivers/clk/mediatek/clk-mux.h b/drivers/clk/mediatek/clk-mux.h
> > new file mode 100644
> > index 000000000000..ff0276bb771c
> > --- /dev/null
> > +++ b/drivers/clk/mediatek/clk-mux.h
> > @@ -0,0 +1,101 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (c) 2018 MediaTek Inc.
> > + * Author: Owen Chen <owen.chen@mediatek.com>
> > + */
> > +
> > +#ifndef __DRV_CLK_MUX_H
> > +#define __DRV_CLK_MUX_H
> > +
> > +#include <linux/clk-provider.h>
> > +
> > +struct mtk_clk_mux {
> > + struct clk_hw hw;
> > + struct regmap *regmap;
> > +
> > + const char *name;
> > +
> > + u32 mux_set_ofs;
> > + u32 mux_clr_ofs;
> > + u32 mux_ofs;
> > + u32 upd_ofs;
> > +
> > + u8 mux_shift;
> > + u8 mux_width;
> > + u8 gate_shift;
> > + u8 upd_shift;
> > +
> > + spinlock_t *lock;
> > +};
> > +
> > +struct mtk_mux {
> > + int id;
> > + const char *name;
> > + const char * const *parent_names;
> > + unsigned int flags;
> > +
> > + u32 mux_ofs;
> > + u32 set_ofs;
> > + u32 clr_ofs;
> > + u32 upd_ofs;
> > +
> > + u8 mux_shift;
> > + u8 mux_width;
> > + u8 gate_shift;
> > + u8 upd_shift;
> > +
> > + const struct clk_ops *ops;
> > +
> > + signed char num_parents;
> > +};
> > +
> > +extern const struct clk_ops mtk_mux_ops;
> > +extern const struct clk_ops mtk_mux_clr_set_upd_ops;
> > +extern const struct clk_ops mtk_mux_gate_ops;
> > +extern const struct clk_ops mtk_mux_gate_clr_set_upd_ops;
> > +
> > +#define GATE_CLR_SET_UPD_FLAGS(_id, _name, _parents, _mux_ofs, \
> > + _mux_set_ofs, _mux_clr_ofs, _shift, _width, \
> > + _gate, _upd_ofs, _upd, _flags, _ops) { \
> > + .id = _id, \
> > + .name = _name, \
> > + .mux_ofs = _mux_ofs, \
> > + .set_ofs = _mux_set_ofs, \
> > + .clr_ofs = _mux_clr_ofs, \
> > + .upd_ofs = _upd_ofs, \
> > + .mux_shift = _shift, \
> > + .mux_width = _width, \
> > + .gate_shift = _gate, \
> > + .upd_shift = _upd, \
> > + .parent_names = _parents, \
> > + .num_parents = ARRAY_SIZE(_parents), \
> > + .flags = _flags, \
> > + .ops = &_ops, \
> > + }
> > +
> > +#define MUX_GATE_CLR_SET_UPD_FLAGS(_id, _name, _parents, _mux_ofs, \
> > + _mux_set_ofs, _mux_clr_ofs, _shift, _width, \
> > + _gate, _upd_ofs, _upd, _flags) \
> > + GATE_CLR_SET_UPD_FLAGS(_id, _name, _parents, _mux_ofs, \
> > + _mux_set_ofs, _mux_clr_ofs, _shift, _width, \
> > + _gate, _upd_ofs, _upd, _flags, \
> > + mtk_mux_gate_clr_set_upd_ops)
> > +
> > +#define MUX_GATE_CLR_SET_UPD(_id, _name, _parents, _mux_ofs, \
> > + _mux_set_ofs, _mux_clr_ofs, _shift, _width, \
> > + _gate, _upd_ofs, _upd) \
> > + MUX_GATE_CLR_SET_UPD_FLAGS(_id, _name, _parents, \
> > + _mux_ofs, _mux_set_ofs, _mux_clr_ofs, _shift, \
> > + _width, _gate, _upd_ofs, _upd, \
> > + CLK_SET_RATE_PARENT)
> > +
> > +struct clk *mtk_clk_register_mux(const struct mtk_mux *mux,
> > + struct regmap *regmap,
> > + spinlock_t *lock);
> > +
> > +int mtk_clk_register_muxes(const struct mtk_mux *muxes,
> > + int num, struct device_node *node,
> > + spinlock_t *lock,
> > + struct clk_onecell_data *clk_data);
> > +
> > +#endif /* __DRV_CLK_MUX_H */
> > --
> > 2.18.0
> >
>
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