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Message-ID: <CAMuHMdV2-YrktT+=D2LVFw5oR+6EOLcPB_Yuh5wnos099W9YHQ@mail.gmail.com>
Date: Mon, 13 Oct 2025 16:21:07 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, 
	Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Biju Das <biju.das.jz@...renesas.com>, Magnus Damm <magnus.damm@...il.com>, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org, 
	linux-clk@...r.kernel.org, Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v10 2/6] clk: renesas: rzv2h-cpg: Add support for DSI clocks

On Thu, 9 Oct 2025 at 18:07, Prabhakar <prabhakar.csengg@...il.com> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> 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@...esas.com>
> Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
> 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.

> +       i = 0;

Ditto; or better: in the variable declaration at the top of the function.

> +       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:
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

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

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