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

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Date:	Wed, 27 Jul 2016 08:42:10 +0800
From:	Caesar Wang <wxt@...k-chips.com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Caesar Wang <wxt@...k-chips.com>, devicetree@...r.kernel.org,
	heiko@...ech.de, linux-iio@...r.kernel.org, dianders@...omium.org,
	linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	robh+dt@...nel.org, john@...anate.com,
	linux-arm-kernel@...ts.infradead.org, jic23@...nel.org
Subject: Re: [PATCH v2 1/4] iio: adc: rockchip_saradc: reset saradc controller
 before programming it

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@...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.
>>
> 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 
.....

>
> Guenter
>
>> 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
>>
>>
> _______________________________________________
> 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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