Re: [DO NOT MERGE v6 14/37] clk: Compatible with narrow registers

Hi Sato-san,

On Tue, Jan 9, 2024 at 9:24 AM Yoshinori Sato
<[email protected]> wrote:
> 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 <[email protected]>

Thanks for your patch!

> --- a/drivers/clk/clk-gate.c
> +++ b/drivers/clk/clk-gate.c
> @@ -143,6 +161,18 @@ struct clk_hw *__clk_hw_register_gate(struct device *dev,
>                         return ERR_PTR(-EINVAL);
>                 }

Please add a check for invalid CLK_GATE_HIWORD_MASK
and register width combinations:

                if (clk_gate_flags & (CLK_GATE_REG_16BIT | CLK_GATE_REG_8BIT)) {
                        pr_err("HIWORD_MASK needs 32-bit registers\n");
                        return ERR_PTR(-EINVAL);
                }

>         }
> +       if (clk_gate_flags & CLK_GATE_REG_16BIT) {
> +               if (bit_idx > 15) {
> +                       pr_err("gate bit exceeds 16 bits\n");
> +                       return ERR_PTR(-EINVAL);
> +               }
> +       }
> +       if (clk_gate_flags & CLK_GATE_REG_8BIT) {
> +               if (bit_idx > 7) {
> +                       pr_err("gate bit exceeds 8 bits\n");
> +                       return ERR_PTR(-EINVAL);
> +               }
> +       }
>
>         /* allocate the gate */
>         gate = kzalloc(sizeof(*gate), GFP_KERNEL);
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index ace3a4ce2fc9..e2dfc1f083f4 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -508,12 +508,16 @@ 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;
>         void __iomem    *reg;
>         u8              bit_idx;
> -       u8              flags;
> +       u32             flags;

There is no need to increase the size of the flags field for the gate clock.

>         spinlock_t      *lock;
>  };
>
> @@ -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)
>
>  extern const struct clk_ops clk_gate_ops;
>  struct clk_hw *__clk_hw_register_gate(struct device *dev,

The rest LGTM.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds