Re: quick help on PDM DAC driver

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Sep 22, 2014 at 07:28:43PM +0530, Naidu Tellapati wrote:
> Hi Thierry,
> 
> Many thanks for your continued help in this regard.
> 
> Each bit in my 12-bit input value to the PDM block does not in anyway
> corresponds to fixed interval. My hardware PDM block works with the
> following simple logic
> 
> counter [12:0] = counter [11:0] + pluse_in [11:0]     /* pulse_in is a
> 12-bit input value to PDM block */
> pdm_out = counter [12]
> 
> The above logic runs for every pdm_clk cycle.

I don't see how this could reasonably fake a PWM. The best you can
probably get is a 0%, 50% and 100% duty-cycles.

> And hence I am of the opinion that I need to have a Linux PDM
> Framework which is similar to PWM Framework and which provides
> pulse_in as device attribute to the Linux User Space.

Given the peculiarity of the device I don't think adding a framework is
necessary. But you could perhaps add a driver to drivers/misc that
exposes the pulse_in parameter in sysfs.

Thierry

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