On 7/18/08, Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Jul 18, 2008 at 03:44:37PM -0400, Jon Smirl wrote:
> > On 7/18/08, Jon Smirl <jonsmirl@xxxxxxxxx> wrote:
>
>
> > > 3) Something Freescale calls cellphone slave but it is more like clock
> > > distribution.
>
> > > In cellslave mode one i2s port is in normal slave mode. The clock from
> > > this port is used to drive up to three other i2s ports in master mode.
>
>
> ...
>
>
> > > When the clock frequency changes I need to notify the i2s drivers for
> > > the dependent channels. Do we need a third choice,
> > > SND_SOC_CLOCK_SLAVE? Alternatively I can use another clock id value.
>
>
> Without having looked at how this works in hardware I'd probably
> implement this by using a different clock id for the slave ports if I
> wanted to use set_sysclk() to configure cell slave mode. It sounds like
> you've got to choose between two sources within the SoC, one being that
> clocked in from the external source and the other regular clocks. From
> what you're saying as far as the individual I2S port is concerned it is
> the master in both cases.
That might work better. Currently I was setting cellslave mode at boot
time from the device tree. But by using different clock ids it can be
set dynamically.
> > switch (dir) {
> > case SND_SOC_CLOCK_IN:
> > return 0;
> > case SND_SOC_CLOCK_OUT:
> > default:
> > if (!(psc_i2s->sicr & MPC52xx_PSC_SICR_CELLSLAVE)) {
> > /* implement me */
> > /* compute and set the needed dividers for the internal clock */
> > return -EINVAL;
> > }
> > psc_i2s->sysclk = freq;
> > return -EINVAL;
> > }
> > }
>
>
> If you did use a separate clock id then you could set or clear
> MPC52xx_PSC_SICR_CELLSLAVE as appropriate here which might be a bit
> easier to write. It depends on what's clearer and what work is needed
> to configure the slave mode - I guess there may be other configuration
> required?
>
> Having said that the important thing here is that what you do is
> sensible and idiomatic for people working on the platform so it may be
> that what you've got already is the most expressive thing. The clock
> configuration is done by machine drivers which will obviously be
> platform specific.
>
--
Jon Smirl
jonsmirl@xxxxxxxxx
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