From: Sven Van Asbroeck <thesven73@gmail.com>
To: Philipp Zabel <pza@pengutronix.de>
Cc: Nicolas Dufresne <nicolas@ndufresne.ca>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Adrian Ratiu <adrian.ratiu@collabora.com>,
Lucas Stach <l.stach@pengutronix.de>,
Fabio Estevam <festevam@gmail.com>,
linux-media <linux-media@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [BUG REPORT] media: coda: mpeg4 decode corruption on i.MX6qp only
Date: Fri, 12 Feb 2021 18:52:34 -0500 [thread overview]
Message-ID: <CAGngYiWAohHXYPfd5NJc4URVuMA4GP01jvRV78uM5P+H7zKx-A@mail.gmail.com> (raw)
In-Reply-To: <20210211143233.GA1360@pengutronix.de>
Philipp, Fabio,
I was able to verify that the PREs do indeed overrun their allocated ocram area.
Section 38.5.1 of the iMX6QuadPlus manual indicates the ocram size
required: width(pixels) x 8 lines x 4 bytes. For 2048 pixels max, this
comes to 64K. This is what the PRE driver allocates. So far, so good.
The trouble starts when we're displaying a section of a much wider
bitmap. This happens in X when using two displays. e.g.:
HDMI 1920x1088
LVDS 1280x800
X bitmap 3200x1088, left side displayed on HDMI, right side on LVDS.
In such a case, the stride will be much larger than the width of a
display scanline.
This is where things start to go very wrong.
I found that the ocram area used by the PREs increases with the
stride. I experimentally found a formula:
ocam_used = display_widthx8x4 + (bitmap_width-display_width)x7x4
As the stride increases, the PRE eventually overruns the ocram and...
ends up in the "ocram aliased" area, where it overwrites the ocram in
use by the vpu/coda !
I could not find any PRE register setting that changes the used ocram area.
Sven
next prev parent reply other threads:[~2021-02-12 23:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 16:33 [BUG REPORT] media: coda: mpeg4 decode corruption on i.MX6qp only Sven Van Asbroeck
2021-02-10 16:11 ` Nicolas Dufresne
2021-02-10 18:11 ` Sven Van Asbroeck
2021-02-10 18:29 ` Sven Van Asbroeck
2021-02-11 14:32 ` Philipp Zabel
2021-02-11 15:15 ` Sven Van Asbroeck
2021-02-12 23:52 ` Sven Van Asbroeck [this message]
2021-02-15 10:15 ` Lucas Stach
2021-02-15 15:54 ` Sven Van Asbroeck
2021-02-15 16:10 ` Lucas Stach
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