Re: [PATCH v2 3/6] clk: sunxi-ng: nkm: Support minimum and maximum rate

Frank Oltmanns
2024-02-21T10:39:01Z

Hi Jernej,
hi Maxime,

On 2024-02-05 at 16:22:26 +0100, Frank Oltmanns <frank@oltmanns.dev> wrote:
> According to the Allwinner User Manual, the Allwinner A64 requires
> PLL-MIPI to run at 500MHz-1.4GHz. Add support for that to ccu_nkm.

I should point out that limiting PLL-MIPI also fixes a regression
that was introduced in 6.5, specifically
ca1170b69968233b34d26432245eddf7d265186b "clk: sunxi-ng: a64: force
select PLL_MIPI in TCON0 mux". This has been bisected and reported by
Diego [1].

I don't know the procedure (yet), but probably the fix (if and when
accepted) should be backported at least to 6.6 (first broken LTS), 6.7
(stable), and 6.8 (next stable).

My suggestion:
- In V3 of this series, I will reorder the patches, so that what is now
PATCH 3 and 4 becomes 1 and 2 respectively, so that they can be
applied to 6.6 more easily.
- Maxime, IIUC you requested some refactoring for handling the rate
limits [2]. I propose, we use my current proposal as-is, and I will
do a follow-up series for the refactoring.

Please let me know how you would like me to proceed.

Thanks,
Frank

[1]: https://groups.google.com/g/linux-sunxi/c/Rh-Uqqa66bw
[2]: https://lore.kernel.org/all/exb2lvjcozak5fayrgyenrd3ntii4jfxgvqork4klyz5pky2aq@dj2zyw5su6pv/

>
> Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
> ---
> drivers/clk/sunxi-ng/ccu_nkm.c | 13 +++++++++++++
> drivers/clk/sunxi-ng/ccu_nkm.h | 2 ++
> 2 files changed, 15 insertions(+)
>
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
> index 1168d894d636..7d135908d6e0 100644
> --- a/drivers/clk/sunxi-ng/ccu_nkm.c
> +++ b/drivers/clk/sunxi-ng/ccu_nkm.c
> @@ -181,6 +181,12 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
> if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
> rate *= nkm->fixed_post_div;
>
> + if (nkm->min_rate && rate < nkm->min_rate)
> + rate = nkm->min_rate;
> +
> + if (nkm->max_rate && rate > nkm->max_rate)
> + rate = nkm->max_rate;
> +
> if (!clk_hw_can_set_rate_parent(&nkm->common.hw))
> rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm, &nkm->common);
> else
> @@ -220,6 +226,13 @@ static int ccu_nkm_set_rate(struct clk_hw *hw, unsigned long rate,
> _nkm.min_m = 1;
> _nkm.max_m = nkm->m.max ?: 1 << nkm->m.width;
>
> +
> + if (nkm->min_rate && rate < nkm->min_rate)
> + rate = nkm->min_rate;
> +
> + if (nkm->max_rate && rate > nkm->max_rate)
> + rate = nkm->max_rate;
> +
> ccu_nkm_find_best(parent_rate, rate, &_nkm, &nkm->common);
>
> spin_lock_irqsave(nkm->common.lock, flags);
> diff --git a/drivers/clk/sunxi-ng/ccu_nkm.h b/drivers/clk/sunxi-ng/ccu_nkm.h
> index c409212ee40e..358a9df6b6a0 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 min_rate;
> + unsigned long max_rate;
> unsigned long max_m_n_ratio;
> unsigned long min_parent_m_ratio;