linux-kernel - Re: [PATCH] iio: adc: rockchip_saradc: Explicitly disable ADC on probe

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Message-ID: <8ebf4c53-21e2-0220-1756-beb57af32304@kernel.org>
Date:	Mon, 15 Aug 2016 19:04:31 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Guenter Roeck <linux@...ck-us.net>,
	Caesar Wang <wxt@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>
Cc:	linux-iio@...r.kernel.org, dianders@...omium.org,
	linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH] iio: adc: rockchip_saradc: Explicitly disable ADC on
 probe

On 26/07/16 04:22, Guenter Roeck wrote:
> On 07/25/2016 07:51 PM, Caesar Wang wrote:
>> Hi Guenter,
>>
>> Thanks for fixing it.
>>
>> On 2016年07月26日 03:39, Guenter Roeck wrote:
>>> If the ADC is read for the first time, the caller gets a timeout error,
>>> and the kernel log shows
>>>
>>> read channel() error: -110
>>>
>>> The ADC may be enabled on boot, and needs to be explicitly disabled
>>> for a read sequence to work (otherwise there is no completion interrupt).
>>> Disaple it explicitly in the probe function.
>>>
>>> Fixes: 44d6f2ef94f9 ("iio: adc: add driver for Rockchip saradc")
>>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>>> ---
>>>   drivers/iio/adc/rockchip_saradc.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/iio/adc/rockchip_saradc.c b/drivers/iio/adc/rockchip_saradc.c
>>> index f9ad6c2d6821..6aa3271d86b5 100644
>>> --- a/drivers/iio/adc/rockchip_saradc.c
>>> +++ b/drivers/iio/adc/rockchip_saradc.c
>>> @@ -280,6 +280,9 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
>>>           goto err_pclk;
>>>       }
>>> +    /* Make sure ADC is disabled */
>>> +    writel_relaxed(0, info->regs + SARADC_CTRL);
>>
>> I think we should reset the saradc controller.
>> Since make sure the reset value is 0 and loader-->kernel may even cause harm, as my experience on tsadc. (drivers/thermal/rockchip_thermal.c)
>>
>>
>> e.g.:
>> /**
>> * Reset SARADC Controller, reset all saradc registers.
>> */
>> static void rockchip_saradc_reset_controller(struct reset_control *reset)
>> {
>> reset_control_assert(reset);
>> usleep_range(10, 20);
>> reset_control_deassert(reset);
>> }
>>
>> ..probe()
>> {
>> ...
>> rockchip_saradc_reset_controller();
>> ...
>> }
>>
> 
> Ok, I'll give it a try.
> 
> Guenter
Could you confirm if this patch is superseded by that
change or not?
> 
>>
>> -
>> Caesar
>>
>>> +
>>>       platform_set_drvdata(pdev, indio_dev);
>>>       indio_dev->name = dev_name(&pdev->dev);
>>
>>
> 
> -- 
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