Re: [PATCH v2 1/6] clk: sunxi-ng: nkm: Support constraints on m/n ratio and parent rate

Jernej Škrabec
2024-02-05T17:45:31Z

Dne ponedeljek, 05. februar 2024 ob 16:22:24 CET je Frank Oltmanns napisal(a):
> The Allwinner A64 manual lists the following constraints for the
> PLL-MIPI clock:
> - M/N <= 3
> - (PLL_VIDEO0)/M >= 24MHz
>
> The PLL-MIPI clock is implemented as ccu_nkm. Therefore, add support for
> these constraints.
>
> Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>

Haven't we discussed that this patch is unnecessary because same effect can
be reached by limiting minimum frequency?

Best regards,
Jernej

> ---
> drivers/clk/sunxi-ng/ccu_nkm.c | 21 +++++++++++++++++++++
> drivers/clk/sunxi-ng/ccu_nkm.h | 2 ++
> 2 files changed, 23 insertions(+)
>
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
> index 853f84398e2b..1168d894d636 100644
> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
> @@ -16,6 +16,20 @@ struct _ccu_nkm {
> unsigned long m, min_m, max_m;
> };
>
> +static bool ccu_nkm_is_valid_rate(struct ccu_common *common, unsigned long parent,
> + unsigned long n, unsigned long m)
> +{
> + struct ccu_nkm *nkm = container_of(common, struct ccu_nkm, common);
> +
> + if (nkm->max_m_n_ratio && (m > nkm->max_m_n_ratio * n))
> + return false;
> +
> + if (nkm->min_parent_m_ratio && (parent < nkm->min_parent_m_ratio * m))
> + return false;
> +
> + return true;
> +}
> +
> static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_common *common,
> struct clk_hw *parent_hw,
> unsigned long *parent, unsigned long rate,
> @@ -31,6 +45,10 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_common *common
> unsigned long tmp_rate, tmp_parent;
>
> tmp_parent = clk_hw_round_rate(parent_hw, rate * _m / (_n * _k));
> +
> + if (!ccu_nkm_is_valid_rate(common, tmp_parent, _n, _m))
> + continue;
> +
> tmp_rate = tmp_parent * _n * _k / _m;
>
> if (ccu_is_better_rate(common, rate, tmp_rate, best_rate) ||
> @@ -64,6 +82,9 @@ static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
> for (_k = nkm->min_k; _k <= nkm->max_k; _k++) {
> for (_n = nkm->min_n; _n <= nkm->max_n; _n++) {
> for (_m = nkm->min_m; _m <= nkm->max_m; _m++) {
> + if (!ccu_nkm_is_valid_rate(common, parent, _n, _m))
> + continue;
> +
> unsigned long tmp_rate;
>
> tmp_rate = parent * _n * _k / _m;
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.h b/drivers/clk/sunxi-ng/ccu_nkm.h
> index 6601defb3f38..c409212ee40e 100644
> --- a/drivers/clk/sunxi-ng/ccu_nkm.h
> +++ b/drivers/clk/sunxi-ng/ccu_nkm.h
> @@ -27,6 +27,8 @@ struct ccu_nkm {
> struct ccu_mux_internal mux;
>
> unsigned int fixed_post_div;
> + unsigned long max_m_n_ratio;
> + unsigned long min_parent_m_ratio;
>
> struct ccu_common common;
> };
>
>