From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>,
devicetree@vger.kernel.org, jsarha@ti.com,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v2 2/2] drm/omap: partial workaround for DRA7xx DMM errata i878
Date: Wed, 04 Apr 2018 13:28:16 +0300 [thread overview]
Message-ID: <3403759.MX1QIus5OE@avalon> (raw)
In-Reply-To: <8dd97211-a4b4-cd8e-f9ef-896adfb95d81@ti.com>
Hi Tomi,
On Wednesday, 4 April 2018 13:02:04 EEST Tomi Valkeinen wrote:
> On 04/04/18 12:51, Laurent Pinchart wrote:
> > On Wednesday, 4 April 2018 10:37:05 EEST Tomi Valkeinen wrote:
> >> On 04/04/18 00:11, Laurent Pinchart wrote:
> >>> I assume access to DMM-mapped buffers to be way more frequent than
> >>> access to the DMM registers. If that's the case, this partial workaround
> >>> should only slightly lower the probability of system lock-up. Do you
> >>> have plans to implement a workaround that will fix the problem
> >>> completely ?
> >>
> >> CPU only accesses memory via DMM when using TILER 2D buffers, which are
> >> not officially supported. For non-2D, the pages are mapped directly to
> >> the CPU without DMM in between.
> >
> > What is the DMM used for with non-2D then ? Does it need to be setup at
> > all ?
>
> It creates a contiguous view of memory for IPs without IOMMUs, like DSS.
OK, got it. In that case the CPU accesses don't need to go through the DMM,
only the device accesses do, as the CPU will go through the MMU. Sorry for the
noise.
--
Regards,
Laurent Pinchart
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next prev parent reply other threads:[~2018-04-04 10:28 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-22 13:42 [PATCH v2 0/2] drm/omap: Workaround for errata i878 Peter Ujfalusi
2018-03-22 13:42 ` [PATCH v2 1/2] dt-bindings: arm: omap: dmm: Document new compatible for DRA7xx family Peter Ujfalusi
2018-03-23 8:31 ` Peter Ujfalusi
2018-04-03 20:48 ` Laurent Pinchart
2018-03-26 22:24 ` Rob Herring
2018-04-03 20:44 ` Laurent Pinchart
2018-03-22 13:42 ` [PATCH v2 2/2] drm/omap: partial workaround for DRA7xx DMM errata i878 Peter Ujfalusi
2018-03-23 8:32 ` Peter Ujfalusi
2018-03-29 10:18 ` Tomi Valkeinen
2018-03-29 12:11 ` Peter Ujfalusi
2018-04-03 21:11 ` Laurent Pinchart
2018-04-04 7:37 ` Tomi Valkeinen
2018-04-04 9:51 ` Laurent Pinchart
2018-04-04 10:02 ` Tomi Valkeinen
2018-04-04 10:28 ` Laurent Pinchart [this message]
2018-04-04 10:33 ` Tomi Valkeinen
2018-04-04 11:17 ` Laurent Pinchart
2018-04-04 10:50 ` Tomi Valkeinen
2018-04-04 11:08 ` Laurent Pinchart
2018-04-10 6:50 ` Peter Ujfalusi
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