On Fri, Dec 08, 2017 at 04:35:09PM +0800, Chen-Yu Tsai wrote: > Hi, > > This series follows previous improvements for the other Allwinner SoCs to > improve audio quality, in particular the speed and pitch of audio playback. > The audio PLLs in Allwinner SoCs cannot produce the correct frequency to > match the audio sample rate families through integer factors. As such > the audio is either too fast or too flow. > > This is dealt with by using sigma-delta modulation, a form of fractional-N > synthesis, on the divider. The parameters used are copied from the BSP > kernel. > > As these parameters assume that one of the untracked dividers is set to > 2, we first add a fixed /2 post divider to the PLL, and force the > untracked divider to /2. Then we introduce the sigma-delta modulation > parameters. > > This has been tested with SPDIF playback on the Cubietruck Plus, and an > external PCM5122 DAC from a PiFi DAC 2.0+, connected via I2S to the > Banana Pi M3. The I2C and I2S support used in this latter test will be > sent as a separate series later.
Applied, thanks! Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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