linux-kernel - Re: [RFC PATCH v1 0/4] Add Rockchip RGA support

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Date:	Mon, 28 Mar 2016 20:44:44 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Emil Velikov <emil.l.velikov@...il.com>
Cc:	Yakir Yang <ykk@...k-chips.com>, David Airlie <airlied@...ux.ie>,
	Mark Yao <mark.yao@...k-chips.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Russell King <linux@....linux.org.uk>,
	devicetree <devicetree@...r.kernel.org>,
	linux-kernel@...r.kernel.org,
	ML dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-rockchip <linux-rockchip@...ts.infradead.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v1 0/4] Add Rockchip RGA support

Am Montag, 28. März 2016, 13:21:02 schrieb Emil Velikov:
> On 22 March 2016 at 00:42, Heiko Stuebner <heiko@...ech.de> wrote:
> > Hi Yakir,
> > 
> > Am Montag, 21. März 2016, 20:17:46 schrieb Yakir Yang:
> >> On 03/21/2016 07:29 PM, Heiko Stübner wrote:
> >> > Am Montag, 21. März 2016, 17:28:38 schrieb Yakir Yang:
> >> >> This patch set would add the RGA direct rendering based 2d graphics
> >> >> acceleration module.
> >> > 
> >> > very cool to see that.
> >> 
> >> ;)
> >> 
> >> >> This patch set is based on git repository below:
> >> >> git://people.freedesktop.org/~airlied/linux drm-next
> >> >> commit id: 568d7c764ae01f3706085ac8f0d8a8ac7e826bd7
> >> >> 
> >> >> And the RGA driver is based on Exynos G2D driver, it only manages the
> >> >> command lists received from user, so user should make the command list
> >> >> to data and registers needed by operation to use.
> >> >> 
> >> >> I have prepared an userspace demo application for testing:
> >> >>    https://github.com/yakir-Yang/libdrm-rockchip
> >> >> 
> >> >> That is a rockchip libdrm library, and I have write a simple test case
> >> >> "rockchip_rga_test" that would test the below RGA features:
> >> >> - solid
> >> >> - copy
> >> >> - rotation
> >> >> - flip
> >> >> - window clip
> >> >> - dithering
> >> > 
> >> > Did you submit your libdrm changes as well?
> >> > 
> >> > Userspace-interfaces need to be stable so the other side must also get
> >> > accepted - even before the kernel change if I remember correctly.
> >> 
> >> Got it, and I just saw exynos_fimg2d already landed at mainline libdrm.
> >> But I don't find the way to submit patches to libdrm, would you like
> >> share some helps here ;)
> > 
> > Looking at the libdrm sources on cgit.freedesktop.org, I did not find any
> > specific manual on submitting patches.
> > 
> > But looking at the dri-list archive, dri-devel@...ts.freedesktop.org is
> > the
> > right list and looking at the libdrm history it looks like Emil Velikov
> > <emil.l.velikov@...il.com> seems to be doing maintenance-stuff in libdrm.
> > And as a 3rd recipient, please also include the linux-rockchip list.
> > 
> > @Emil, please shout if I read that wrong :-)
> 
> You got it spot on Heiko. There are a few notes though...
> 
> As one reuses the existing hardware/IP block, it would be better to
> avoid copy/pasting code around.
> Namely:
>  - (if possible) factor out the exynos g2d kernel functionality to a
> separate kernel module and wire up the rockhip (via dt ?) to use it
>  - factor out the g2d specifics out of exynos_drm.h (into
> exynos_g2d_drm.h perhaps ?) and make sure exynos_drm.h includes the
> new header

I think the IP blocks themself are quite different between Rockchip's RGA and 
Samsung's g2d and I guess the similarities are more along the lines on how 
that gets integrated into the respective drm driver and userspace.


>  - if neither of these are possible, then please ensure that the new
> header uses correct types (see the docs [1]), use MIT/X11 license (if
> possible) and link where upstream userspace is happy with the
> interface (ideally more than a simple test app like libdrm)
> These might sound like an overkill, although getting UAPI right and
> maintaining it forever forces us to do so.

As for a real-world usecase, maybe the armsoc xserver might be somewhat easy 
to use. While the core changes I did are in the core project already, I'm 
still keeping the actual Rockchip support separate [0] due to the not-yet-
resolved create_gem ioctl.

Anyway, the armsoc xserver has some exa implementation hooks were I guess it 
might be relatively easy to hook up soc-specific things.

[0] https://github.com/mmind/xf86-video-armsoc/tree/devel/rockchip