Re: [alsa-devel] [PATCH 15/27] ALSA: hda - Use timecounter_initialize interface

[Pierre-Louis Bossart]

On 1/2/18 12:03 AM, Sagar Arun Kamble wrote:
> On 12/28/2017 10:19 PM, Richard Cochran wrote:
> > On Tue, Dec 26, 2017 at 01:07:35PM +0530, Sagar Arun Kamble wrote:
> > > > Or can we provide simpler versions for covering some defaults? At
> > > > least reducing the number of arguments would make things easier.
> > > Thought about specifying 1. cyclecounter read func 2. frequency 3. 
> > > width of
> > > counter as parameters here
> > > which can get rid of mult, shift params. But this is not easy as most 
> > > of the
> > > drivers do not specify
> > > cyclecounter frequency and instead hard-code the mult/shift factors.
> > You are talking about using clocks_calc_mult_shift() here, right? (See
> > the usage example in drivers/net/ethernet/ti/cpts.c).
> Yes
> > This is a good idea, and it is worth getting the driver authors' input
> > to figure out the correct parameters.

I wrote the code for HDaudio and I remember wasting time trying to 
figure out the gory details of the cycle counter stuff when all I wanted 
was a conversion from a 24MHz counter to ns values using a 125/3 
operation in the right order - as explained in the comments

If there was a helper to set those mult/shift values it'd make the 
HDaudio code clearer (and also help support newer modes of operation 
with a 12 and 6 MHz MCLK).

The initial proposal with hard-coded values in arguments instead of 
structure members didn't really make the code clearer.


> > I bet we can use that almost everywhere. If there are any drivers
> > that cannot be converted, then we can leave some sort of low level
> > legacy initialization method.
> Agree
> > Thanks,
> > Richard
>
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