From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Date: Thu, 15 Mar 2012 22:28:11 +0000 Subject: Re: [PATCH 1/2] OMAPDSS: DISPC: Enable predecimation Message-Id: <20120315222811.GN17132@sci.fi> List-Id: References: <1331812108-9776-1-git-send-email-cmahapatra@ti.com> In-Reply-To: <1331812108-9776-1-git-send-email-cmahapatra@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: Chandrabhanu Mahapatra Cc: tomi.valkeinen@ti.com, linux-omap@vger.kernel.org, linux-fbdev@vger.kernel.org On Thu, Mar 15, 2012 at 05:18:28PM +0530, Chandrabhanu Mahapatra wrote: > In OMAP3 and OMAP4, the DISPC Scaler can downscale an image up to 4 times= , and > up to 2 times in OMAP2. However, with predecimation, the image can be red= uced > to 16 times by fetching only the necessary pixels in memory. Then this > predecimated image can be downscaled further by the DISPC scaler. Now, where does that number 16 come from? IIRC the hardware can skip basically any number of pixels/rows. I certainly didn't add any such limit to the code in the harmattan kernel, and distinctly remember being able to downscale the N9/N950 UI even down to 1 pixel size :) > Based on the downscaling required, a prior calculation of predecimation v= alues > for width and height of an image is done. Since, Predecimation reduces qu= ality > of an image higher priorty is given to DISPC Scaler for downscaling. >=20 > This code was successfully tested on OMAP2, OMAP3 and OMAP4. Horizontal a= nd > vertical predecimation worked fine except for some synclost errors due to > undocumented errata in OMAP3 which are fixed later and skewed images were= seen > on OMAP2 and OMAP3 during horizontal predecimation which will be addresse= d in > the future patches. All the rotation offset calculations still look suspiciously different to what is in the harmattan kernel. I remember that the original code was quite broken, and I fixed a lot of things when I was implementing pre-decimation and some rotation stuff for the N9/N950. Too bad I never managed to push that stuff upstream... --=20 Ville Syrj=E4l=E4 syrjala@sci.fi http://www.sci.fi/~syrjala/