linux-kernel - Re: [PATCH 11/17] drm: renesas: rz-du: mipi

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Message-ID: <CA+V-a8uh-LUmLEs_85dXwuiYecJTyLt3zd06vyGE749Ye+9moQ@mail.gmail.com>
Date: Mon, 31 Mar 2025 16:27:22 +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>, 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>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Kieran Bingham <kieran.bingham+renesas@...asonboard.com>, Stephen Boyd <sboyd@...nel.org>, 
	Philipp Zabel <p.zabel@...gutronix.de>, 
	"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-media@...r.kernel.org" <linux-media@...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 11/17] drm: renesas: rz-du: mipi_dsi: Add OF data support

Hi Biju,

On Mon, Mar 31, 2025 at 4:04 PM Biju Das <biju.das.jz@...renesas.com> wrote:
>
> Hi Prabhakar,
>
> > -----Original Message-----
> > From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> > Sent: 31 March 2025 15:44
> > Subject: Re: [PATCH 11/17] drm: renesas: rz-du: mipi_dsi: Add OF data support
> >
> > Hi Biju,
> >
> > On Mon, Mar 31, 2025 at 3:14 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> > > > Sent: 31 March 2025 14:59
> > > > 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>; 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>; Mauro Carvalho Chehab
> > > > <mchehab@...nel.org>; Kieran Bingham
> > > > <kieran.bingham+renesas@...asonboard.com>; Stephen Boyd
> > > > <sboyd@...nel.org>; Philipp Zabel <p.zabel@...gutronix.de>;
> > > > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > > linux-renesas- soc@...r.kernel.org; linux-media@...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 11/17] drm: renesas: rz-du: mipi_dsi: Add OF
> > > > data support
> > > >
> > > > Hi Biju,
> > > >
> > > > Thank you for the review.
> > > >
> > > > On Mon, Mar 31, 2025 at 1:38 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > >
> > > > > Hi Prabhakar,
> > > > >
> > > > > Thanks for the patch.
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Prabhakar <prabhakar.csengg@...il.com>
> > > > > > Sent: 30 March 2025 22:07
> > > > > > Subject: [PATCH 11/17] drm: renesas: rz-du: mipi_dsi: Add OF
> > > > > > data support
> > > > > >
> > > > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > > >
> > > > > > In preparation for adding support for the Renesas RZ/V2H(P) SoC,
> > > > > > this patch introduces a mechanism to pass SoC-specific
> > > > > > information via OF data in the DSI driver. This enables the
> > > > > > driver to adapt dynamically to various SoC-
> > > > specific requirements without hardcoding configurations.
> > > > > >
> > > > > > The MIPI DSI interface on the RZ/V2H(P) SoC is nearly identical
> > > > > > to the one on the RZ/G2L SoC. While the LINK registers are
> > > > > > shared between the two SoCs, the D-PHY registers differ. Also
> > > > > > the VCLK range differs on both these SoCs. To accommodate these
> > > > > > differences `struct rzg2l_mipi_dsi_hw_info`
> > > > is introduced and as now passed as OF data.
> > > > > >
> > > > > > These changes lay the groundwork for the upcoming RZ/V2H(P) SoC
> > > > > > support by allowing SoC-specific data to be passed through OF.
> > > > > >
> > > > <snip>
> > > > > > +
> > > > > >       ret = drm_of_get_data_lanes_count_ep(dsi->dev->of_node, 1, 0, 1, 4);
> > > > > >       if (ret < 0)
> > > > > >               return dev_err_probe(dsi->dev, ret, @@ -729,10
> > > > > > +750,12 @@ static int rzg2l_mipi_dsi_probe(struct platform_device *pdev)
> > > > > >       if (IS_ERR(dsi->vclk))
> > > > > >               return PTR_ERR(dsi->vclk);
> > > > > >
> > > > > > -     dsi->rstc = devm_reset_control_get_exclusive(dsi->dev, "rst");
> > > > > > -     if (IS_ERR(dsi->rstc))
> > > > > > -             return dev_err_probe(dsi->dev, PTR_ERR(dsi->rstc),
> > > > > > -                                  "failed to get rst\n");
> > > > > > +     if (dsi->info->has_dphy_rstc) {
> > > > > > +             dsi->rstc =
> > > > > > + devm_reset_control_get_exclusive(dsi->dev,
> > > > > > + "rst");
> > > > >
> > > > > Maybe use devm_reset_control_get_optional_exclusive by dropping has_dphy_rstc.
> > > > >
> > > > As the dtbs_check doesn't enforce this,  `has_dphy_rstc` flag was
> > > > added. Recently the same was done for the CRU [0] based on the recent comment received.
> > > >
> > >
> > > RZ/V2H has "arst" and "prst". So, If you add "rst" for RZ/V2H then you should get dtbs warning,
> > right?
> > >
> > No we dont [0], note DT binding is written based on the recent feedback received.
>
> That is strange. It is triggering warning for me, if I just update the example.
>
Ahh right I missed that. The current implementation is based on this
comment received [0] (same being applied for reset). Please let me
know if you still want me to use
devm_reset_control_get_optional_exclusive() (and same for the clk).

[0] https://lore.kernel.org/lkml/20250223181955.GD8330@pendragon.ideasonboard.com/

Cheers,
Prabhakar