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

[Caesar Wang]

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)
> >
> >
> > 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.

I posted it on https://patchwork.kernel.org/patch/9247661/


> Guenter
>
> > -
> > Caesar
> >
> > > +
> > >       platform_set_drvdata(pdev, indio_dev);
> > >       indio_dev->name = dev_name(&pdev->dev);
>
>
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--
caesar wang | software engineer | wxt@xxxxxxxxxxxxx