Re: [PATCH v2 1/4] iio: adc: rockchip_saradc: reset saradc controller before programming it

[Guenter Roeck]

On 07/26/2016 05:42 PM, Caesar Wang wrote:
> On 2016å07æ27æ 01:00, Guenter Roeck wrote:
> > On Tue, Jul 26, 2016 at 10:47:16PM +0800, Caesar Wang wrote:
> > > On 2016å07æ26æ 21:39, Guenter Roeck wrote:
> > > > > static int rockchip_saradc_probe(struct platform_device *pdev)
> > > > > {
> > > > > struct rockchip_saradc *info = NULL;
> > > > > @@ -218,6 +231,21 @@ static int rockchip_saradc_probe(struct
> > > > > platform_device *pdev)
> > > > > if (IS_ERR(info->regs))
> > > > > return PTR_ERR(info->regs);
> > > > >
> > > > > + /*
> > > > > + * The reset should be an optional property, as it should work
> > > > > + * with old devicetrees as well
> > > > > + */
> > > > > + info->reset = devm_reset_control_get_optional(&pdev->dev,
> > > > > + "saradc-apb");
> > > > Does anyone know what the _optional API is for ? It seems to be exactly
> > > > the same
> > > > as devm_reset_control_get().
> > > â
> > > As far as I see, the difference is WARN_ON(1)
> > > when CONFIG_RESET_CONTROLLER is not defined.
> > >
> > >
> > > The _optional functions were introduced by the following commit:
> > >
> > > ----------------->8-----------------
> > > commit b424080a9e086e683ad5fdc624a7cf3c024e0c0f
> > > Author: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> > > Date: Fri Mar 7 15:18:47 2014 +0100
> > >
> > > reset: Add optional resets and stubs
> > >
> > > This patch adds device_reset_optional and (devm_)reset_control_get_optional
> > > variants that drivers can use to indicate they can function without control
> > > over the reset line. For those functions, stubs are added so the drivers can
> > > be compiled with CONFIG_RESET_CONTROLLER disabled.
> > > Also, device_reset is annotated with __must_check. Drivers
> > > ignoring the return
> > > value should use device_reset_optional instead.
> > Is that really what we are looking for here ? CONFIG_RESET_CONTROLLER
> > is required for other functions of rk3399, isn't it ?
>
> Right, as the DRM and thermal are depend on the CONFIG_RESET_CONTROLLER .....

Since "optional" doesn't really mean "the reset property is optional"
but "CONFIG_RESET_CONTROLLER is optional", I would suggest to use
devm_reset_control_get().

Guenter