On Sat, Feb 07, 2015 at 06:32:29AM +0800, Mark Brown wrote: > On Thu, Feb 05, 2015 at 12:53:36PM -0800, Kenneth Westfield wrote: > > > This patch series adds support for I2S audio playback on the Qualcomm > > Technologies ipq806x SOC. > > > The ipq806x SOC has audio-related hardware blocks in its low-power audio > > subsystem (or LPASS). One of the relevant blocks in the LPASS is its low-power > > audio interface (or LPAIF). This contains an MI2S port, which is what these > > drivers are configured to use. The LPAIF also contains a DMA engine that is > > dedicated to moving audio samples into the transmit FIFO of the MI2S port. In > > addition, there is also low-power memory (LPM) within the audio subsystem, which > > is used for buffering the audio samples. > > This is implementing an AP centric audio system design where the AP > directly programs all the audio hardware. Given that pretty much all > public Qualcomm systems use a DSP centric model where the AP interacts > only with a DSP which deals with DMA and the physical interfaces it > seems reasonable to suppose that this system also has a DSP which at > some future point people are likely to want to use. > > I'd really like to see some discussion as to how this is all supposed to > be handled - how will these direct hardware access drivers and device > trees work when someone does want to use the DSP (without causing > problems), and how will we transition from one to the other. This is > particularly pressing if there are use cases where people will want to > switch between the two modes at runtime. > > What I'm trying to avoid here is being in a situation where we have > existing stable DT bindings which we have to support but which conflict > with the way that people want to use the systems. The ipq806x SOC has no LPASS DSP. On SOCs with a DSP, these drivers would not be enabled. These drivers are prefixed with "lpass" to differentiate themselves from other drivers that would interact with a DSP, rather than the LPASS hardware directly. -- Kenneth Westfield Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
