From mboxrd@z Thu Jan 1 00:00:00 1970 From: wens@csie.org (Chen-Yu Tsai) Date: Sun, 20 Jul 2014 12:18:22 +0800 Subject: [linux-sunxi] GSoC 2014 #1 status report - Improving Allwinner SoC support In-Reply-To: <53CAC9ED.9080302@elopez.com.ar> References: <53BE0B4F.1090001@elopez.com.ar> <53CAC9ED.9080302@elopez.com.ar> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Emilio, On Sun, Jul 20, 2014 at 3:41 AM, Emilio L?pez wrote: > Hi everyone, > > Here's this week's update on my GSoC project; if you missed the first issue > or you want a refresher of what this is about, you can read it on the list > archives[0] > > A couple of days after the last report, and with the help of Jon Smirl, I > got the hardware working on mainline Linux, first on only 16 bit stereo > mode, then mono as well, and later on, also on 24 bit mode. The first thing > I had to do was rework the cyclic DMA code to make it perform decently and > avoid underruns. The rest took a bit of playing with values and reading the > Allwinner documentation. There is one unresolved issue with 24 bit audio > still - for some reason, the volume is really low compared to the same track > played on 16 bit. Unfortunately the SDK driver doesn't support 24 bit, so > it's hard to compare with anything else. So I have not experimented on this, it's just a hunch: Could it be that the 24bit audio samples you're sending to the audio codec is aligned incorrectly? So the sample is actually seen as down-shifted by 8 bits, resulting in the low volume? I'll grab your tree and test 24bit tomorrow. (Good thing I have 24 bit music files.) :) > Aside from the audio stuff, I worked a bit on the DMA driver, after > realizing memcpy could be optimized a fair bit. By using proper alignment > and choosing the best bus width and as big a burst as possible, I was able > to go from a totally unscientifically measured ~3MB/s to ~13MB/s on a single > thread, single channel, 1000 iterations dmatest run with noverify=0. I will > be sending a v3 with these new changes as well as addressing comments I > received in the next few days. This still seems quite slow? I think there was a discussion about this on IRC, you included? Any followups there? > To round up on this week's developments, I also worked on the audio clock > representation, involving PLL2, the codec clock gate and "module 1" clocks > (AC97, SPDIF, IIS) to enable Jon to work on IIS. Patches for these clocks > will be out in the list soon as well. Thanks! I look forward to them. Cheers ChenYu > You can expect the next status report in about a week's time. > > Cheers! > > Emilio > > [0] > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-July/271150.html