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

Nicolas Boichat
2018-11-13T16:00:37Z

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(...).

> +}
> +
> +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(...) .

> +}
> +
> +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.

> +
> + 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).

> +}
> +
> +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...

> +
> + 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.

> +
> + 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?

> +
> + 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.

> + 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)

> +
> + 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.

> + 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.

> + 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

> + 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?

> +
> + 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?

> + }
> +
> + 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
>