Hi Philipp,
On 2021/12/1, 5:12 PM, "Philipp Zabel" <p.zabel@xxxxxxxxxxxxxx> wrote:
Hi Billy,
On Wed, 2021-12-01 at 03:30 +0000, Billy Tsai wrote:
> > Hi Philipp,
> >
> > On 2021/11/30, 5:52 PM, "Philipp Zabel" <p.zabel@xxxxxxxxxxxxxx> wrote:
> >
> > On Mon, 2021-11-29 at 14:43 +0800, Billy Tsai wrote:
> > [...]
> > > > + ret = clk_prepare_enable(priv->clk);
> > > > + if (ret)
> > > > + return dev_err_probe(dev, ret, "Couldn't enable clock\n");
> > > > +
> > > > + ret = reset_control_deassert(priv->reset);
> > > > + if (ret) {
> > > > + dev_err_probe(dev, ret, "Couldn't deassert reset control\n");
> > > > + goto err_disable_clk;
> > > > + }
> >
> > > Is there any reason to keep the clocks running and the controller out of
> > > reset while the PWM outputs are disabled?
> >
> > Can you tell me about your concerns with this process?
> No particular concerns, just curiosity.
> > In my opinion, they are used to provide the clock and de-assert the reset of the PWM engine. If we didn't release
> > them in probe stage the CPU can't and shouldn't read the register of the PWM engine when call the get_state.
> > Assume that we want to adjust them dynamically, the driver needs to add more conditions to check and keep the status
> > of each PWM channel, which is not a good deal for the server platform.
> Thanks. I don't know the hardware, so I have no idea whether disabling
> the clocks would even save a measurable (let alone appreciable) amount
> of power.
> I've just seen other PWM drivers use runtime PM or enable/disable clocks
> dynamically, and wondered why this one doesn't.
Thanks for the heads up, I think that for the usage we don't need to implement that.
Best Regards,
Billy Tsai
