linux-kernel - Re: [PATCH v6 4/4] drm: renesas: rz-du: mipi

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Message-ID: <CA+V-a8tKm4yjEG_ZbajXcgTdOB=GxqA=kt63svJ4ZF609tXHDA@mail.gmail.com>
Date: Mon, 16 Jun 2025 12:20:53 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>, 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>, 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>, 
	Magnus Damm <magnus.damm@...il.com>, 
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>, 
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v6 4/4] drm: renesas: rz-du: mipi_dsi: Add support for
 RZ/V2H(P) SoC

Hi Biju,

On Mon, Jun 16, 2025 at 11:54 AM Biju Das <biju.das.jz@...renesas.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> > Sent: Monday, June 16, 2025 11:48 AM
> > To: Biju Das <biju.das.jz@...renesas.com>
> > Cc: Geert Uytterhoeven <geert+renesas@...der.be>; 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>; 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>; 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>;
> > Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
> > Subject: Re: [PATCH v6 4/4] drm: renesas: rz-du: mipi_dsi: Add support for
> > RZ/V2H(P) SoC
> >
> > Hi Biju,
> >
> > Thank you for the review.
> >
> > On Fri, Jun 13, 2025 at 7:17 AM Biju Das <biju.das.jz@...renesas.com>
> > wrote:
> > >
> > > Hi Prabhakar,
> > >
> > > > -----Original Message-----
> > > > From: Prabhakar <prabhakar.csengg@...il.com>
> > > > Sent: 30 May 2025 18:19
> > > > Subject: [PATCH v6 4/4] drm: renesas: rz-du: mipi_dsi: Add support
> > > > for RZ/V2H(P) SoC
> > > >
> > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > >
> > > > Add DSI support for Renesas RZ/V2H(P) SoC.
> > > >
> > > > 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>
> > > > ---
> > > > v5->v6:
> > > > - Made use of GENMASK() macro for PLLCLKSET0R_PLL_*,
> > > >   PHYTCLKSETR_* and PHYTHSSETR_* macros.
> > > > - Replaced 10000000UL with 10 * MEGA
> > > > - Renamed mode_freq_hz to mode_freq_khz in rzv2h_dsi_mode_calc
> > > > - Replaced `i -= 1;` with `i--;`
> > > > - Renamed RZV2H_MIPI_DPHY_FOUT_MIN_IN_MEGA to
> > > >   RZV2H_MIPI_DPHY_FOUT_MIN_IN_MHZ and
> > > >   RZV2H_MIPI_DPHY_FOUT_MAX_IN_MEGA to
> > > >   RZV2H_MIPI_DPHY_FOUT_MAX_IN_MHZ.
> > > >
> > > > v4->v5:
> > > > - No changes
> > > >
> > > > v3->v4
> > > > - In rzv2h_dphy_find_ulpsexit() made the array static const.
> > > >
> > > > v2->v3:
> > > > - Simplifed V2H DSI timings array to save space
> > > > - Switched to use fsleep() instead of udelay()
> > > >
> > > > v1->v2:
> > > > - Dropped unused macros
> > > > - Added missing LPCLK flag to rzv2h info
> > > > ---
> > > >  .../gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c    | 345
> > ++++++++++++++++++
> > > >  .../drm/renesas/rz-du/rzg2l_mipi_dsi_regs.h   |  34 ++
> > > >  2 files changed, 379 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> > > > b/drivers/gpu/drm/renesas/rz- du/rzg2l_mipi_dsi.c index
> > > > a31f9b6aa920..ea554ced6713 100644
> > > > --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> > > > +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> > > > @@ -5,6 +5,7 @@
> > > >   * Copyright (C) 2022 Renesas Electronics Corporation
> > > >   */
> > > >  #include <linux/clk.h>
> > > > +#include <linux/clk/renesas-rzv2h-dsi.h>
> > > >  #include <linux/delay.h>
> > > >  #include <linux/io.h>
> > > >  #include <linux/iopoll.h>
> > <snip>
> > > > +
> > > > +static int rzv2h_dphy_conf_clks(struct rzg2l_mipi_dsi *dsi, unsigned
> > long mode_freq,
> > > > +                             u64 *hsfreq_millihz) {
> > > > +     struct rzv2h_plldsi_parameters *dsi_parameters = &dsi-
> > >dsi_parameters;
> > > > +     unsigned long status;
> > > > +
> > > > +     if (dsi->mode_calc.mode_freq_khz != mode_freq) {
> > > > +             status = rzv2h_dphy_mode_clk_check(dsi, mode_freq);
> > > > +             if (status != MODE_OK) {
> > > > +                     dev_err(dsi->dev, "No PLL parameters found for
> > mode clk %lu\n",
> > > > +                             mode_freq);
> > > > +                     return -EINVAL;
> > > > +             }
> > > > +     }
> > > > +
> > > > +     clk_set_rate(dsi->vclk, dsi->mode_calc.mode_freq_hz);
> > >
> > > Not sure, Can we use the DSI divider required based on the data rate
> > > (vclk, bpp and numlanes) here
> > >
> > > and then the set parent clk of PLLDSI as well here (dsi->vclk * the
> > divider value) ??
> > >
> > > 24MHZ->PLL DSI->DSI DIVIDER->VCLOCK
> > >
> > > Maybe then the clock framework has all the information for setting
> > PLL_DSI and DSI_DIVIDER clks??
> > >
> > Can you please elaborate here with a detailed example.
>
> There will be determine_clk followed by set_clock for setting new rate for PLL DSI(dsi->vclk * the divider value)
> For eg:  vclk_max = 187.5 MHz, DSI Divider required = 16
> Then set PLL_DSI = 187.5 * 16 MHz using clk_set.
>
You mean to use `clk_set_rate(dsi->vclk, (clk_get_rate(dsi->vclk) *
dsi_divider));` ?

Cheers,
Prabhakar