Re: [PATCH v15 3/5] drm: renesas: Add RZ/G2L DU Support

From: Maxime Ripard <mripard@kernel.org>
To: Biju Das <biju.das.jz@bp.renesas.com>
Cc: Fabrizio Castro <fabrizio.castro.jz@renesas.com>,
	"biju.das.au" <biju.das.au@gmail.com>,
	Magnus Damm <magnus.damm@gmail.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"linux-renesas-soc@vger.kernel.org"
	<linux-renesas-soc@vger.kernel.org>,
	Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Subject: Re: [PATCH v15 3/5] drm: renesas: Add RZ/G2L DU Support
Date: Fri, 15 Dec 2023 15:24:22 +0100	[thread overview]
Message-ID: <he23e5al3hinegebvq7qai4jdw3qjgbzmnx34xgxqnu3hw4jke@dts2vi5kcs4u> (raw)
In-Reply-To: <TYCPR01MB1126964899D432355ACAF49D18693A@TYCPR01MB11269.jpnprd01.prod.outlook.com>

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On Fri, Dec 15, 2023 at 01:25:48PM +0000, Biju Das wrote:
> Hi Maxime Ripard,
> 
> > -----Original Message-----
> > From: Maxime Ripard <mripard@kernel.org>
> > Sent: Friday, December 15, 2023 10:24 AM
> > Subject: Re: [PATCH v15 3/5] drm: renesas: Add RZ/G2L DU Support
> > 
> > On Thu, Dec 14, 2023 at 03:24:17PM +0000, Biju Das wrote:
> > > Hi Maxime Ripard,
> > >
> > > Thanks for the feedback.
> > 
> > Thanks, that's super helpful. The architecture is thus similar to vc4
> > 
> > Some general questions related to bugs we had at some point with vc4:
> > 
> >   * Where is the display list stored? In RAM or in a dedicated SRAM?
> 
> [1] It is in DDR (RAM).
> 
> > 
> >   * Are the pointer to the current display list latched?
> > 
> >   * Is the display list itself latched? If it's not, what happens when
> >     the display list is changed while the frame is being generated?
> 
> There is some protocol defined for SW side and HW side for updating display list
> See [1] 33.4.8.1 Operation flow of VSPD and DU.
> 
> All the display list operations are manged here[2]
> 
> [1] https://www.renesas.com/us/en/document/mah/rzg2l-group-rzg2lc-group-users-manual-hardware-0
> 
> [2] https://elixir.bootlin.com/linux/v6.7-rc5/source/drivers/media/platform/renesas/vsp1/vsp1_dl.c#L863

I'm sorry, but I'm not going to read a 3500+ to try to figure it out.
Could you answer the questions above?

Maxime

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