On Wed, 2014-09-10 at 15:26 -0600, Stephen Warren wrote: > No, definitely not; this patch has significant semantic changes since I > reviewed it. OK, sorry. Admittedly this was probably a little bit too quick a shot. The solution looked so clean and on first sight worked just fine. > I'm not sure how this can work. Certainly all 3 clocks that are required > for audio are mentioned here. However, the PLL_A clock (which then > trickles down to the other 2) needs to have its rate changed based on > whether the sample rate is 44.1KHz- or 48KHz-based. Semantically, this > can't be something that "simple-audio-card" can imply, since > "simple-audio-card" is something agnostic to any HW, whereas this > clocking requirement is something specific to Tegra HW. Yes, now as you mention it I forgot about the whole tegra_asoc_utils_set_rate() stuff! > To see the problem, try encoding some audio stream as both 44.1KHz and > 48KHz, then play a few seconds of each and keep switching back and > forth. You'll likely find either the playback pitch is wrong, or you get > drop-outs or stuttering. Yeah, right. Clocks seem to be stuck at the 44.1 kHz setting. > I also wonder how "simple-audio-card" can know what rate the EXTERN1 > clock to the CODEC should be set to; each CODEC has a different > requirement for the minimum clock input and the Fs multiple usually > varies for different sample rates. See for example > sound/soc/tegra/tegra_wm8903.c:tegra_wm8903_hw_params(). This could be a > solved problem though: Perhaps some API has been added to CODECs to > report this information (or perhaps CODEC drivers now clk_set_rate() on > their input clocks themselves) since I last looked. If there are no objections I will just revive version 1 again and send it around as a new version 3 just to prevent any further confusion. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
