Re: [PATCH V0] ASoC: pxa-ssp: add TISSP mode support

[Qiao Zhou <zhouqiao@marvell.com>]

On 11/10/2013 05:29 PM, Daniel Mack wrote:
> On 11/08/2013 02:52 AM, Qiao Zhou wrote:
>> On 11/06/2013 07:24 PM, Mark Brown wrote:
>>> On Tue, Nov 05, 2013 at 04:30:08PM +0800, Qiao Zhou wrote:
>>>> add TISSP mode support. with this mode enabled, ssp controller
>>>> works in TI-ssp protocol automatically and doesn't need to
>>>> configure sspsp register to set the timing for tx/rx.
>>>
>>> What is TISSP mode in an audio context?
>> It's normal SSP mode, and it has a pulse of one bit clock width, which
>> is the frame start signal. previously it's mainly used for voice call
>> which is mono stream. current I2S or DSP_x format use PSP, which
>> configures the details of transmit/receive timing. we can also use PSP
>> to suit this SSP format. But since the SSP controller provides such HW
>> convenience, so we want to add it. I'm not sure it's proper, and want to
>> ask for suggestions.
>
> This sounds like a special case you want to address, rather than
> something that should be recognized by the core.
>
> The question is what you want to achive here. What kind of peripheral do
> you have connected to the other side of the PXA, and why does it need
> this special needle peak on the frame clock rather than a 50% duty-cycle?
The frame format is like the DSP Mode A in WM8994 spec, and the 
peripheral is a normal codec interface for voice call usage, 
mono-stream, 16 bits.
Here I want to add such SSP mode support in pxa-ssp driver, instead of 
using PSP mode to configure detailed data format in PSP register.
should I handle it under DSP_A case with extra param notifying whether 
it's SSP mode or PSP mode? on the peripheral side, the configuration of 
CODEC DAI should be the same.

below are the modes definition in pxa2xx_ssp.h
#define SSCR0_TISSP	(1 << 4)	/* TI Sync Serial Protocol */
#define SSCR0_PSP	(3 << 4)	/* PSP - Programmable Serial Protocol */
>
> Also, I vaguely remember huge problems we had in setting up the SSP
> controller of a PXA SoC. The SSP IP would do all sort of things instead
> of what's described in the docs. Which silicon are you working on?
The silicon now I'm working on is pxa-9xx chips, but it's the same back 
to pxa-3xx chips.
>
>
> Thanks,
> Daniel
>
-- 

Best Regards
Qiao