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

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On 07/26/2016 05:42 PM, Caesar Wang wrote:

On 2016年07月27日 01:00, Guenter Roeck wrote:
On Tue, Jul 26, 2016 at 10:47:16PM +0800, Caesar Wang wrote:
On 2016年07月26日 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().
“
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

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