[alsa-devel] [PATCH 1/4] ASOC: tegra: move AC97 clock defines to the controller node

Lucas Stach dev at lynxeye.de
Tue Jul 23 22:37:47 CEST 2013

Am Dienstag, den 23.07.2013, 09:47 -0700 schrieb Stephen Warren:
> On 07/21/2013 02:28 PM, Lucas Stach wrote:
> > Different from other Tegra sound controllers drivers, the AC97
> > controller driver uses the tegra asoc utils directly to request the
> > needed clocks, as they are needed at AC97 init time. Move the DT clock
> > defines to the right place.
> I'm not convinced this is the correct approach.
> The machine driver needs to manage these clocks, so that it can
> co-ordinate between different audio paths. For example, consider a
> system that supports two different I2S paths. In HW, if both are active
> at once, these need to both run at a derivative of 48KHz or both run at
> a derivative of 44.1KHz. The machine driver is the central place that
> enforces that, and should eventually automatically place constraints on
> one stream when another is configured for a specific sample rate. By the
> same argument, AC'97 can't be a special case here, in case there's some
> system with both AC'97 and I2S hooked up.

I find it highly unlikely to find any Tegra 20 board with such a
configuration. But as your argument is technically correct, I'll try to
fix things up the right way and see how big the impact is.


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