Nice to hear that! Hopefully AW get out of their a*s, and provide helpful documentation and perhaps, also some monetary incentive as well!
It will be nice to see at the end of the project a full mainlined implementation with nice Graphics ( media ) capabilities which are differential of these Socs for the great majority of users out there. R On Wednesday, July 9, 2014 10:41:16 PM UTC-5, Emilio López wrote: > > Hi everyone, > > As some of you may know, I'm currently participating in Google Summer of > Code under the Linux Foundation, working on a proposal titled "Improve > Allwinner SoCs support on mainline Linux". There is a great quantity of > devices out there that are powered by Allwinner processors, including > but not limited to the various Cubieboards, OLinuXinos, STBs, Tablets > and “Mini PCs”. However, to date, support on mainline Linux is not yet > feature complete. My proposal on particular focuses on DMA and analog > audio on the earlier SoCs, and improved A23 support. > > The idea here is to make a weekly status report of the project. As we > are starting mid-program, this one will be a bit different and I'll > outline what has been worked on so far since the beginning. > > To date, I have been mainly working on the DMA driver for sun4i, sun5i > and sun7i. Despite having completely different drivers on SDK kernels, > the hardware block looks and behaves the same, so we are using a single > driver for these three SoC families. I have sent a series of patches[1] > as well as a follow-up v2[2], and I will keep iterating over it until > it's accepted. I have also sent two trivial patches[3][4] as a > side-effect. > > The main challenges while writing this driver can be summarized as a > lack of documentation. First of all, it took me a bit to get to know > DMAEngine. As there is not much documentation on it, most of my learning > took place by reading pre-existing drivers and consulting with my > mentor. Secondly, as the Allwinner documentation is mostly a register > list with bitfield details, I also had to read the SDK drivers and do > some trial and error testing to discover magic values and understand > others. > > Lately, I have also been working on the audio part, now that I have a > working DMA driver. After implementing cyclic DMA transfers and some > clock code, and armed with a Buildroot image with mpg123 and an OpenBSD > release track[5] in mp3 format, I've been trying to get some sound out > of my Cubietruck's headphone jack, but without much success so far. I > have verified my userspace stack and hardware by running these same > binaries on top of the linux-sunxi 3.4 kernel, and it worked fine. I > have since then been dumping relevant registers with devmem and > comparing them, resolving issues as I see them - hopefully this will > yield some audible results. > > Interestingly enough, Allwinner themselves do not seem to be using > cyclic DMA transfers on their driver[6]. I hope this is not a sign of a > hardware bug that's not documented. > > To give some closure to this status report, I'd like to thank Maxime for > his mentoring so far, Ezequiel for letting me pick his brain, and the > Linux Foundation and Google for giving me this opportunity, as well as > everyone on the kernel and sunxi communities who have come forward to > review and test patches. You can expect a new report soon, in about a > week's time or less. > > Emilio > > [1] http://www.spinics.net/lists/dmaengine/msg01148.html > [2] http://www.spinics.net/lists/arm-kernel/msg344766.html > [3] https://lkml.org/lkml/2014/5/11/166 > [4] https://lkml.org/lkml/2014/7/1/486 > [5] http://www.openbsd.org/lyrics.html, maybe I should consider using > some other song for better luck > [6] > > https://github.com/linux-sunxi/linux-sunxi/blob/sunxi-3.4/sound/soc/sunxi/sunxi-codec.c#L1137 > > -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
