[alsa-devel] [PATCH 15/31] ASoC: dmaengine: add custom DMA config to snd_dmaengine_pcm_config

[Lars-Peter Clausen]

On 11/15/2013 09:54 PM, Stephen Warren wrote:
> From: Stephen Warren <swarren at nvidia.com>
> 
> Add fields to struct snd_dmaengine_pcm_config to allow custom:
> 
> - DMA channel names.
> 
>   This is useful when the default "tx" and "rx" channel names don't
>   apply, for example if a HW module supports multiple channels, each
>   having different DMA channel names. This is the case with the FIFOs
>   in Tegra's AHUB. This new facility can replace
>   SND_DMAENGINE_PCM_FLAG_CUSTOM_CHANNEL_NAME.
> 
> - DMA device
> 
>   This allows requesting DMA channels for a device other than the device
>   which is registering the "PCM" driver. This is quite unusual, but is
>   currently useful on Tegra. In much HW, and in Tegra20, each DAI HW
>   module contains its own FIFOs which DMA writes to. However, in Tegra30,
>   the DMA FIFOs were split out AHUB HW module, which then routes the data
>   through a cross-bar, and into the DAI HW modules. However, the current
>   ASoC driver structure does not expose this detail, and acts as if the
>   FIFOs are still part of the DAI HW modules. Consequently, the "PCM"
>   driver is registered with the DAI HW module, yet the DMA channels must
>   be looked up in the AHUB HW module's device tree node. This new config
>   field allows that to happen. Eventually, the Tegra drivers will be
>   reworked to fully expose the AHUB, and this config field can be
>   removed.
> 
> Cc: treding at nvidia.com
> Cc: linux-tegra at vger.kernel.org
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: Liam Girdwood <lgirdwood at gmail.com>
> Cc: Mark Brown <broonie at kernel.org>
> Cc: alsa-devel at alsa-project.org
> Signed-off-by: Stephen Warren <swarren at nvidia.com>

Acked-by: Lars-Peter Clausen <lars at metafoo.de>