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

From: Caesar Wang
Date: Tue Jul 26 2016 - 02:48:51 EST

On 2016å07æ26æ 11:22, Guenter Roeck wrote:
On 07/25/2016 07:51 PM, Caesar Wang wrote:
Hi Guenter,

Thanks for fixing it.

On 2016å07æ26æ 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@xxxxxxxxxxxx>
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)

* Reset SARADC Controller, reset all saradc registers.
static void rockchip_saradc_reset_controller(struct reset_control *reset)
usleep_range(10, 20);


Ok, I'll give it a try.

I posted it on



platform_set_drvdata(pdev, indio_dev);
indio_dev->name = dev_name(&pdev->dev);

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