Re: [PATCH] drm/etnaviv: move GPU linear window to end of DMA window

From: Daniel Vetter <daniel@ffwll.ch>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/etnaviv: move GPU linear window to end of DMA window
Date: Tue, 15 Mar 2016 08:54:40 +0100	[thread overview]
Message-ID: <20160315075440.GR14170@phenom.ffwll.local> (raw)
In-Reply-To: <1457968723.3829.14.camel@pengutronix.de>

On Mon, Mar 14, 2016 at 04:18:43PM +0100, Lucas Stach wrote:
> Am Montag, den 14.03.2016, 15:09 +0000 schrieb Russell King - ARM Linux:
> > On Mon, Mar 14, 2016 at 04:02:35PM +0100, Lucas Stach wrote:
> > > I guess not using the offset on MC10 will also allow you to enable TS on
> > > those parts? In that case we might advertise this with a patchlevel
> > > change of the API.
> > 
> > I don't think we need that - it isn't an API change as such.  What
> > we could do is to clear the fast clear capability for GPUs where the
> > base is non-zero but has MC10, which basically means we don't use
> > tile status.
> > 
> With kernel 4.5 being released now, we already have a kernel version
> that may change the offset, while not clearing the fast clear capability
> bit. So I think we need another way for userspace to know if the kernel
> is doing the right thing for MC10.

btw in drm land we're sometimes a bit sloppy with ABI - if it's just
rendering corruption or maybe oddball gpu hang and small enough to go in
through stable we don't bother to ref the ABI. Instead just ask everyone
to upgrade their kernel once the patch goes through the stable queues.

Otherwise even minor fumbles means ABI complexity forever, and with gpus
that tends to kill you ;-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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