Re: [PATCH v2 6/9] clk: at91: clk-generated: make gclk determine audio_pll rate
From: Alexandre Belloni
Date: Thu Jul 06 2017 - 12:08:48 EST
On 06/07/2017 at 17:29:22 +0200, Nicolas Ferre wrote:
> > + /*
> > + * The audio_pll rate can be modified, unlike the five others clocks
> > + * that should never be altered.
> > + * The audio_pll can technically be used by multiple consumers. However,
> > + * with the rate locking, the first consumer to enable to clock will be
> > + * the one definitely setting the rate of the clock.
> > + * Since audio IPs are most likely to request the same rate, we enforce
> > + * that the only clks able to modify gck rate are those of audio IPs.
> > + */
> > +
> > + if (gck->id != GCK_ID_SSC0 && gck->id != GCK_ID_SSC1 &&
> > + gck->id != GCK_ID_I2S0 && gck->id != GCK_ID_I2S1 &&
> > + gck->id != GCK_ID_CLASSD)
> > + goto end;
> ...well... maybe for a temporary solution, but what about the next
> product that will also have such feature but without the same set of IDs?
It will have a different compatible and that can be used to encode the
> I know that the main use of this clock is the "audio" subsystem (so its
> name) but in a machine without audio needs, it can be interesting to use
> this fractional PLL for other devices that can handle a GCK (and I'm
> thinking about the SDHCI interface that then could be configured with
> maximum clock speed).
> > + parent = clk_hw_get_parent_by_index(hw, GCK_INDEX_DT_AUDIO_PLL);
> > + if (!parent)
> > + goto end;
> Here, if the audio pll id changes in the DT, we don't retrieve the
> proper parent... And again, not very future proof.
One more reason to remove all the crap we have in the DT, as suggested
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering