Re: [DO NOT MERGE v8 14/36] clk: Compatible with narrow registers

[Stephen Boyd <sboyd@kernel.org>]

Quoting Yoshinori Sato (2024-05-29 01:01:00)
> divider and gate only support 32-bit registers.
> Older hardware uses narrower registers, so I want to be able to handle
> 8-bit and 16-bit wide registers.
> 
> Seven clk_divider flags are used, and if I add flags for 8bit access and
> 16bit access, 8bit will not be enough, so I expanded it to u16.
> 
> Signed-off-by: Yoshinori Sato <ysato@users.sourceforge.jp>
> ---
>  drivers/clk/clk-divider.c    | 41 +++++++++++++++++++++---------
>  drivers/clk/clk-gate.c       | 49 ++++++++++++++++++++++++++++++++----
>  include/linux/clk-provider.h | 20 ++++++++++++---
>  3 files changed, 89 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index a2c2b5203b0a..abafcbbb6578 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -26,17 +26,34 @@
>   * parent - fixed parent.  No clk_set_parent support
>   */
>  
> -static inline u32 clk_div_readl(struct clk_divider *divider)
> -{
> +static inline u32 clk_div_read(struct clk_divider *divider)

Please don't change the name. The 'l' is for the return type, u32, which
is not changed.

> +{
> +       if (divider->flags & CLK_DIVIDER_REG_8BIT)
> +               return readb(divider->reg);
> +       if (divider->flags & CLK_DIVIDER_REG_16BIT) {
> +               if (divider->flags & CLK_DIVIDER_BIG_ENDIAN) {
> +                       return ioread16be(divider->reg);
> +               } else {
> +                       return readw(divider->reg);
> +               }
> +       }
>         if (divider->flags & CLK_DIVIDER_BIG_ENDIAN)
>                 return ioread32be(divider->reg);
>  
>         return readl(divider->reg);
>  }
>  
> -static inline void clk_div_writel(struct clk_divider *divider, u32 val)
> +static inline void clk_div_write(struct clk_divider *divider, u32 val)

Same comment.

>  {
> -       if (divider->flags & CLK_DIVIDER_BIG_ENDIAN)
> +       if (divider->flags & CLK_DIVIDER_REG_8BIT)
> +               writeb(val, divider->reg);
> +       else if (divider->flags & CLK_DIVIDER_REG_16BIT) {
> +               if (divider->flags & CLK_DIVIDER_BIG_ENDIAN) {
> +                       iowrite16be(val, divider->reg);
> +               } else {
> +                       writew(val, divider->reg);
> +               }
> +       } else if (divider->flags & CLK_DIVIDER_BIG_ENDIAN)
>                 iowrite32be(val, divider->reg);
>         else
>                 writel(val, divider->reg);
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 4a537260f655..25f61bd5b952 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -508,6 +508,10 @@ void of_fixed_clk_setup(struct device_node *np);
>   * CLK_GATE_BIG_ENDIAN - by default little endian register accesses are used for
>   *     the gate register.  Setting this flag makes the register accesses big
>   *     endian.
> + * CLK_GATE_REG_8BIT - by default 32bit register accesses are used for
> + *     the gate register.  Setting this flag makes the register accesses 8bit.
> + * CLK_GATE_REG_16BIT - by default 32bit register accesses are used for
> + *     the gate register.  Setting this flag makes the register accesses 16bit.
>   */
>  struct clk_gate {
>         struct clk_hw hw;
> @@ -522,6 +526,8 @@ struct clk_gate {
>  #define CLK_GATE_SET_TO_DISABLE                BIT(0)
>  #define CLK_GATE_HIWORD_MASK           BIT(1)
>  #define CLK_GATE_BIG_ENDIAN            BIT(2)
> +#define CLK_GATE_REG_8BIT              BIT(3)
> +#define CLK_GATE_REG_16BIT             BIT(4)

Please add kunit tests for the gate at least.

>  
>  extern const struct clk_ops clk_gate_ops;
>  struct clk_hw *__clk_hw_register_gate(struct device *dev,
> @@ -675,13 +681,17 @@ struct clk_div_table {
>   * CLK_DIVIDER_BIG_ENDIAN - By default little endian register accesses are used
>   *     for the divider register.  Setting this flag makes the register accesses
>   *     big endian.
> + * CLK_DIVIDER_REG_8BIT - by default 32bit register accesses are used for
> + *     the gate register.  Setting this flag makes the register accesses 8bit.
> + * CLK_DIVIDER_REG_16BIT - by default 32bit register accesses are used for
> + *     the gate register.  Setting this flag makes the register accesses 16bit.
>   */
>  struct clk_divider {
>         struct clk_hw   hw;
>         void __iomem    *reg;
>         u8              shift;
>         u8              width;
> -       u8              flags;
> +       u16             flags;
>         const struct clk_div_table      *table;
>         spinlock_t      *lock;
>  };
> @@ -697,6 +707,8 @@ struct clk_divider {
>  #define CLK_DIVIDER_READ_ONLY          BIT(5)
>  #define CLK_DIVIDER_MAX_AT_ZERO                BIT(6)
>  #define CLK_DIVIDER_BIG_ENDIAN         BIT(7)
> +#define CLK_DIVIDER_REG_8BIT           BIT(8)
> +#define CLK_DIVIDER_REG_16BIT          BIT(9)
>  
>  extern const struct clk_ops clk_divider_ops;
>  extern const struct clk_ops clk_divider_ro_ops;
> @@ -726,18 +738,18 @@ struct clk_hw *__clk_hw_register_divider(struct device *dev,
>                 struct device_node *np, const char *name,
>                 const char *parent_name, const struct clk_hw *parent_hw,
>                 const struct clk_parent_data *parent_data, unsigned long flags,
> -               void __iomem *reg, u8 shift, u8 width, u8 clk_divider_flags,
> +               void __iomem *reg, u8 shift, u8 width, u16 clk_divider_flags,

Let's just make this unsigned long for the flags. We don't need to
specify a strict size like this for the callers.

>                 const struct clk_div_table *table, spinlock_t *lock);
>  struct clk_hw *__devm_clk_hw_register_divider(struct device *dev,
>                 struct device_node *np, const char *name,
>                 const char *parent_name, const struct clk_hw *parent_hw,
>                 const struct clk_parent_data *parent_data, unsigned long flags,
> -               void __iomem *reg, u8 shift, u8 width, u8 clk_divider_flags,
> +               void __iomem *reg, u8 shift, u8 width, u16 clk_divider_flags,

Same here.

>                 const struct clk_div_table *table, spinlock_t *lock);
>  struct clk *clk_register_divider_table(struct device *dev, const char *name,
>                 const char *parent_name, unsigned long flags,
>                 void __iomem *reg, u8 shift, u8 width,
> -               u8 clk_divider_flags, const struct clk_div_table *table,
> +               u16 clk_divider_flags, const struct clk_div_table *table,

Same here. Preferably do that in another patch too.