[alsa-devel] [PATCH 10/19] ASoC: Intel: add mrfld DSP registers

[Vinod Koul]

On Fri, Jun 20, 2014 at 02:33:19PM +0200, Lars-Peter Clausen wrote:
> On 06/20/2014 01:32 PM, Vinod Koul wrote:
> >On Fri, Jun 20, 2014 at 10:22:30AM +0200, Lars-Peter Clausen wrote:
> >>On 06/13/2014 02:33 PM, Vinod Koul wrote:
> >>>+unsigned int sst_soc_read(struct snd_soc_platform *platform,
> >>>+			unsigned int reg)
> >>>+{
> >>>+	struct sst_data *drv = snd_soc_platform_get_drvdata(platform);
> >>>+
> >>>+	pr_debug("%s: reg[%d] = %#x\n", __func__, reg, drv->widget[reg]);
> >>>+	BUG_ON(reg > (SST_NUM_WIDGETS - 1));
> >>>+	return drv->widget[reg];
> >>>+}
> >>>+
> >>>+int sst_soc_write(struct snd_soc_platform *platform,
> >>>+		  unsigned int reg, unsigned int val)
> >>>+{
> >>>+	struct sst_data *drv = snd_soc_platform_get_drvdata(platform);
> >>>+
> >>>+	pr_debug("%s: reg[%d] = %#x\n", __func__, reg, val);
> >>>+	BUG_ON(reg > (SST_NUM_WIDGETS - 1));
> >>>+	drv->widget[reg] = val;
> >>>+	return 0;
> >>>+}
> >>
> >>These seem to be purely virtual registers, what is this about? The
> >>DAPM core is able to handle widgets and controls without any
> >>register backing just fine. There is no need to emulate virtual
> >>registers.
> >But we need to store the mixer configuration for sending IPCs to DSP. So virtual
> >register file is very much required
> 
> Hm, ok. But how does this work, when is the IPC triggered and why
> can't the IPC be done from within the write function?
Write can come at any time, even when DSP is inactive. Also we want to tell DSP
about the paths which are active

So most of IPCs are sent from DAPM widget handlers with exception of controls
which are active. For those we send IPC during get/put handlers.

Fwiw, please note the register file is in driver to keep the values for
controls. It is not availble to DSP.

-- 
~Vinod