Re: [PATCH v2] drm/fourcc: add ARM GPU tile format

From: Ayan Halder <Ayan.Halder@arm.com>
To: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Cc: "lima@lists.freedesktop.org" <lima@lists.freedesktop.org>,
	Maxime Ripard <maxime.ripard@bootlin.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	David Airlie <airlied@linux.ie>, Qiang Yu <yuq825@gmail.com>,
	nd <nd@arm.com>, Sean Paul <sean@poorly.run>
Subject: Re: [PATCH v2] drm/fourcc: add ARM GPU tile format
Date: Tue, 12 Mar 2019 15:41:52 +0000	[thread overview]
Message-ID: <20190312154151.GA9309@arm.com> (raw)
In-Reply-To: <20190311163928.GA1412@kevin>

On Mon, Mar 11, 2019 at 09:39:28AM -0700, Alyssa Rosenzweig wrote:
> > You might want to re-use the exisiting modifier
> > AFBC_FORMAT_MOD_BLOCK_SIZE_16x16.
> > 
> > I would suggest you to have a look at the exisiting AFBC modifiers
> > (denoted by AFBC_FORMAT_MOD_XXX ) and let us know if there is
> > something you cannot reuse.
> 
> So, the "tiled" format in question (that Qiang needs to import/export
> BOs in) is *uncompressed* but tiled with an Arm-internal format (for the
> GPUs).  Here's a software implementation for encoding this format:
> https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/panfrost/pan_swizzle.c
>
ok I understood now. In this case, please ignore my suggestion.

> For Midgard/Bifrost, we use this tiling internally for uploading bitmap
> textures, but we only render to AFBC (or linear). So for Panfrost, we'll
> always be importing/exporting AFBC buffers, never uncompressed tiled.

I am not a gpu guy so can't comment at the moment.

> But Utgard does not seem to support AFBC (?), so Qiang needs the
> uncompressed tiled for the same purpose Panfrost uses AFBC.
> 
> Is it possible that this is the same tiling used internally by
> AFBC_FORMAT_MOD_BLOCK_SIZE_16x16, only without any compression? AFBC is
> blackbox for us, so this isn't something we can figure out ourselves,
> but that influences whether it's appropriate to reuse the modifier. If
> this is the same tiling scheme, perhaps that's the answer. If it's not
> (I don't know how AFBC tiling works), we probably do need a separate
> modifier to avoid confusion.
>
AFBC_FORMAT_MOD_BLOCK_SIZE_16x16 denotes the superblock size to be
used only in case of AFBC buffers.
For non compressed tiled format, none of the AFBC_FORMAT_MOD_XXX
should be used.

However, I would like you to review my patch series
(https://patchwork.freedesktop.org/series/53395/) to
see if we have the same understanding.

> Thanks,
> 
> Alyssa

> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel