linux-kernel - Re: [PATCH v5 4/4] drm: renesas: rz-du: mipi

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Message-ID: <CAMuHMdXSbEWVpMbDx7UC3Zn3YteZLCdJ=kOOakE38k1TeTxKqA@mail.gmail.com>
Date: Wed, 28 May 2025 14:31:44 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc: Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 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>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 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, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v5 4/4] drm: renesas: rz-du: mipi_dsi: Add support for
 RZ/V2H(P) SoC

Hi Prabhakar,

On Wed, 28 May 2025 at 11:48, Lad, Prabhakar <prabhakar.csengg@...il.com> wrote:
> On Fri, May 23, 2025 at 4:19 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Mon, 12 May 2025 at 20:43, Prabhakar <prabhakar.csengg@...il.com> wrote:
> > > 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>
> >
> > Thanks for your patch!
> >
> > > --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
> > > +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c

> > > @@ -47,6 +52,11 @@ struct rzg2l_mipi_dsi_hw_info {
> > >         u8 features;
> > >  };
> > >
> > > +struct rzv2h_dsi_mode_calc {
> > > +       unsigned long mode_freq;
> > > +       u64 mode_freq_hz;
> >
> > Interesting... I guess mode_freq is not in Hz?
> >
> Actually it is int Hz, I will make it unsigned long.

I really meant the first member.
As rzv2h_dphy_mode_clk_check() does "mode_freq_hz = mode_freq * MILLI",
mode_freq may be in kHz?

> > > +};

> > > @@ -308,6 +479,158 @@ static int rzg2l_dphy_conf_clks(struct rzg2l_mipi_dsi *dsi, unsigned long mode_f
> > >         return 0;
> > >  }
> > >
> > > +static unsigned int rzv2h_dphy_mode_clk_check(struct rzg2l_mipi_dsi *dsi,
> > > +                                             unsigned long mode_freq)
> > > +{
> > > +       struct rzv2h_plldsi_parameters *dsi_parameters = &dsi->dsi_parameters;
> > > +       u64 hsfreq_millihz, mode_freq_hz, mode_freq_millihz;
> > > +       struct rzv2h_plldsi_parameters cpg_dsi_parameters;
> > > +       unsigned int bpp, i;
> > > +
> > > +       bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> > > +
> > > +       for (i = 0; i < 10; i += 1) {
> > > +               unsigned long hsfreq;
> > > +               bool parameters_found;
> > > +
> > > +               mode_freq_hz = mode_freq * MILLI + i;
> >
> > KILO?
> >
> OK, as mode_freq_hz is in Hz I'll make it unsigned long.

I am not sure if "unsigned long" is OK. Is mode_freq in kHz?
What is its largest value?

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