Re: [PATCH RFC v1 1/3] clk: divider: Add re-usable determine_rate implementations

From: Jerome Brunet
Date: Tue May 18 2021 - 03:45:39 EST



On Mon 17 May 2021 at 22:37, Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> wrote:

> These are useful when running on 32-bit systems to increase the upper
> supported frequency limit. clk_ops.round_rate returns a signed long
> which limits the maximum rate on 32-bit systems to 2^31 (or approx.
> 2.14GHz). clk_ops.determine_rate internally uses an unsigned long so
> the maximum rate on 32-bit systems is 2^32 or approx. 4.29GHz.
>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> ---
> drivers/clk/clk-divider.c | 39 +++++++++++++++++++++++++++++++++++-
> include/linux/clk-provider.h | 6 ++++++
> 2 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> index 344997203f0e..24c94d2a3643 100644
> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c
> @@ -377,7 +377,6 @@ long divider_ro_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
> }
> EXPORT_SYMBOL_GPL(divider_ro_round_rate_parent);
>
> -
> static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
> unsigned long *prate)
> {
> @@ -399,6 +398,44 @@ static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
> divider->width, divider->flags);
> }
>
> +int divider_determine_rate(struct clk_hw *hw, struct clk_rate_request *req,
> + const struct clk_div_table *table, u8 width,
> + unsigned long flags)
> +{
> + int div;
> +
> + div = clk_divider_bestdiv(hw, req->best_parent_hw, req->rate,
> + &req->best_parent_rate, table, width, flags);
> +
> + req->rate = DIV_ROUND_UP_ULL((u64)req->best_parent_rate, div);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(divider_determine_rate);
> +
> +int divider_ro_determine_rate(struct clk_hw *hw, struct clk_rate_request *req,
> + const struct clk_div_table *table, u8 width,
> + unsigned long flags, unsigned int val)
> +{
> + int div;
> +
> + div = _get_div(table, val, flags, width);
> +
> + /* Even a read-only clock can propagate a rate change */
> + if (clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT) {
> + if (!req->best_parent_hw)
> + return -EINVAL;
> +
> + req->best_parent_rate = clk_hw_round_rate(req->best_parent_hw,
> + req->rate * div);
> + }
> +
> + req->rate = DIV_ROUND_UP_ULL((u64)req->best_parent_rate, div);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(divider_ro_determine_rate);

For a final version, could you factorize the code with the .round_rate()
variant ? It would remove a bit of duplication.

Maybe determine_rate() can also replace round_rate() in the generic
divider ops ?

> +
> int divider_get_val(unsigned long rate, unsigned long parent_rate,
> const struct clk_div_table *table, u8 width,
> unsigned long flags)
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 162a2e5546a3..d83b829305c0 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -629,6 +629,12 @@ long divider_ro_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
> unsigned long rate, unsigned long *prate,
> const struct clk_div_table *table, u8 width,
> unsigned long flags, unsigned int val);
> +int divider_determine_rate(struct clk_hw *hw, struct clk_rate_request *req,
> + const struct clk_div_table *table, u8 width,
> + unsigned long flags);
> +int divider_ro_determine_rate(struct clk_hw *hw, struct clk_rate_request *req,
> + const struct clk_div_table *table, u8 width,
> + unsigned long flags, unsigned int val);
> int divider_get_val(unsigned long rate, unsigned long parent_rate,
> const struct clk_div_table *table, u8 width,
> unsigned long flags);