Re: [PATCH v10 2/6] clk: renesas: rzv2h-cpg: Add support for DSI clocks

[Lad, Prabhakar]

Hi Geert,

Thank you for the review.

On Mon, Oct 13, 2025 at 3:26 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
>
> On Thu, 9 Oct 2025 at 18:07, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >
> > Add support for PLLDSI and its post-dividers to the RZ/V2H CPG driver and
> > export a set of helper APIs to allow other consumers (notably the DSI
> > driver) to compute and select PLL parameter combinations.
> >
> > Introduce per-PLL-DSI state in the CPG private structure and implement
> > clk ops and registration for PLLDSI and PLLDSI divider clocks. Implement
> > rzv2h_cpg_plldsi_determine_rate and rzv2h_cpg_plldsi_set_rate to drive
> > PLL programming via the new per-PLL state and add a plldsi divider clk
> > with determine/set/recalc operations that cooperate with the PLL
> > algorithm.
> >
> > Centralize PLL parameter types and limits by moving definitions into a
> > shared header (include/linux/clk/renesas.h). Add struct rzv2h_pll_limits,
> > struct rzv2h_pll_pars and struct rzv2h_pll_div_pars, plus the
> > RZV2H_CPG_PLL_DSI_LIMITS() macro to declare DSI PLL limits.
> >
> > Provide two exported helper functions, rzv2h_get_pll_pars() and
> > rzv2h_get_pll_divs_pars(), that perform iterative searches over PLL
> > parameters (M, K, P, S) and optional post-dividers to find the best (or
> > exact) match for a requested frequency. Export these helpers in the
> > "RZV2H_CPG" namespace for use by external drivers.
> >
> > This change centralizes DSI PLL rate selection logic, prevents duplicate
> > implementations in multiple drivers, and enables the DSI driver to
> > request accurate PLL rates and program the hardware consistently.
> >
> > Co-developed-by: Fabrizio Castro <fabrizio.castro.jz@xxxxxxxxxxx>
> > Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@xxxxxxxxxxx>
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > ---
> > v9->v10:
> > - Dropped rzv2h_get_pll_div_pars() helper and opencoded instead.
> > - Dropped rzv2h_get_pll_dtable_pars() helper and opencoded instead.
> > - Added dummy helpers rzv2h_get_pll_pars() and rzv2h_get_pll_divs_pars()
> >   in renesas.h for !CONFIG_CLK_RZV2H case.
> > - Updated commit message.
>
> Thanks for the update!
>
> > --- a/drivers/clk/renesas/rzv2h-cpg.c
> > +++ b/drivers/clk/renesas/rzv2h-cpg.c
>
> > +static int rzv2h_cpg_plldsi_div_determine_rate(struct clk_hw *hw,
> > +                                              struct clk_rate_request *req)
> > +{
> > +       struct rzv2h_plldsi_div_clk *dsi_div = to_plldsi_div_clk(hw);
> > +       struct pll_clk *pll_clk = to_pll(clk_hw_get_parent(hw));
> > +       struct rzv2h_cpg_priv *priv = dsi_div->priv;
> > +       u8 table[RZV2H_MAX_DIV_TABLES] = { 0 };
> > +       struct rzv2h_pll_div_pars *dsi_params;
> > +       struct rzv2h_pll_dsi_info *dsi_info;
> > +       const struct clk_div_table *div;
> > +       u64 rate_millihz;
> > +       unsigned int i;
> > +
> > +       dsi_info = &priv->pll_dsi_info[pll_clk->pll.instance];
> > +       dsi_params = &dsi_info->pll_dsi_parameters;
> > +
> > +       rate_millihz = mul_u32_u32(req->rate, MILLI);
> > +       if (rate_millihz == dsi_params->div.error_millihz + dsi_params->div.freq_millihz)
> > +               goto exit_determine_rate;
> > +
> > +       div = dsi_div->dtable;
>
> This belongs inside the for-initializer below.
>
Agreed.

> > +       i = 0;
>
> Ditto; or better: in the variable declaration at the top of the function.
>
Ok, I will move to the top.

> > +       for (; div->div; div++) {
> > +               if (i >= RZV2H_MAX_DIV_TABLES)
> > +                       return -EINVAL;
> > +               table[i++] = div->div;
> > +       }
> > +
> > +       if (!rzv2h_get_pll_divs_pars(dsi_info->pll_dsi_limits, dsi_params, table, i,
> > +                                    rate_millihz)) {
> > +               dev_err(priv->dev, "failed to determine rate for req->rate: %lu\n",
> > +                       req->rate);
> > +               return -EINVAL;
> > +       }
> > +
> > +exit_determine_rate:
> > +       req->rate = DIV_ROUND_CLOSEST_ULL(dsi_params->div.freq_millihz, MILLI);
> > +       req->best_parent_rate = req->rate * dsi_params->div.divider_value;
> > +       dsi_info->req_pll_dsi_rate = req->best_parent_rate;
> > +
> > +       return 0;
> > +}
>
> The rest LGTM, so with the above fixed, and the field changes factored
> out into a separate patch:
Ok, I will move the field changes into a separate patch.

> Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

Cheers,
Prabhakar