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

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Date:	Tue, 26 Jul 2016 22:47:16 +0800
From:	Caesar Wang <wxt@...k-chips.com>
To:	Guenter Roeck <linux@...ck-us.net>, heiko@...ech.de
CC:	Caesar Wang <wxt@...k-chips.com>, jic23@...nel.org,
	devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org, dianders@...omium.org,
	linux-rockchip@...ts.infradead.org, robh+dt@...nel.org,
	john@...anate.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/4] iio: adc: rockchip_saradc: reset saradc controller
 before programming it

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@...xxxxxxxxxxx>
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.

Signed-off-by: Philipp Zabel <p.zabel@...xxxxxxxxxxx>
------------------8<-----------------------------
”

for more information on 
http://www.spinics.net/lists/kernel/msg2306677.html :-)

>
> Guenter
>
>> + if (IS_ERR(info->reset)) {
>> + ret = PTR_ERR(info->reset);
>> + if (ret != -ENOENT)
>> + return ret;
>> +
>> + dev_dbg(&pdev->dev, "no reset control found\n");
>> + info->reset = NULL;
>> + }
>> +
>> init_completion(&info->completion);
>>
>> irq = platform_get_irq(pdev, 0);
>> @@ -252,6 +280,9 @@ static int rockchip_saradc_probe(struct 
>> platform_device *pdev)
>> return PTR_ERR(info->vref);
>> }
>>
>> + if (info->reset)
>> + rockchip_saradc_reset_controller(info->reset);
>> +
>> /*
>> * Use a default value for the converter clock.
>> * This may become user-configurable in the future.
>>
>
>
> _______________________________________________
> Linux-rockchip mailing list
> Linux-rockchip@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-rockchip

-- 
caesar wang | software engineer | wxt@...k-chip.com

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