Re: [PATCH v6 2/3] media: ov8856: Add devicetree support

[Sakari Ailus]

On Thu, Apr 30, 2020 at 12:11:57PM +0200, Marco Felsch wrote:
> On 20-04-30 12:59, Sakari Ailus wrote:
> > Hi Marco,
> > 
> > On Thu, Apr 30, 2020 at 11:53:32AM +0200, Marco Felsch wrote:
> > > Hi Sakari,
> > > 
> > > On 20-04-30 12:45, Sakari Ailus wrote:
> > > > Hi Marco,
> > > > 
> > > > On Thu, Apr 30, 2020 at 11:35:24AM +0200, Marco Felsch wrote:
> 
> ...
> 
> > > > > > -	if (mclk != OV8856_MCLK) {
> > > > > > -		dev_err(dev, "external clock %d is not supported", mclk);
> > > > > > -		return -EINVAL;
> > > > > > +	if (!is_acpi_node(fwnode)) {
> > > > > > +		ov8856->xvclk = devm_clk_get(dev, "xvclk");
> > > > > > +		if (IS_ERR(ov8856->xvclk)) {
> > > > > > +			dev_err(dev, "could not get xvclk clock (%pe)\n",
> > > > > > +					ov8856->xvclk);
> > > > > > +			return PTR_ERR(ov8856->xvclk);
> > > > > > +		}
> > > > > > +
> > > > > > +		clk_set_rate(ov8856->xvclk, xvclk_rate);
> > > > > > +		xvclk_rate = clk_get_rate(ov8856->xvclk);
> > > > > >  	}
> > > > > 
> > > > > Why do we handle the clock only in DT case? Is there a problem with the
> > > > > clock handling and ACPI?
> > > > 
> > > > Not really, it's just that ACPI does not provide an interface to the clocks
> > > > as such.
> > > 
> > > But you will get a clk by devm_clk_get()?
> > 
> > No, because ACPI does not expose one to drivers. Effectively the entire
> > power sequences are implemented in ACPI, not in the driver.
> > 
> 
> Ah okay, thanks for the explanation. I'm really not into the ACPI
> stuff.. So this means the __power_off / power_on should only be done if
> we are using DT's?

Correct. That's why it bails out early. It could be yet earlier though,
without doing anything.

-- 
Sakari Ailus