Re: [PATCH 2/4] iio: mxs-lradc: add scale attribute to channels

[Hector Palacios <hector.palacios@xxxxxxxx>]

Dear Marek,

On 07/05/2013 01:41 PM, Marek Vasut wrote:
> Dear Hector Palacios,
>
> > Some LRADC channels have a fixed pre-divider, and all can have enabled
> > an optional divisor by two which allows a maximum input voltage of
> > VDDIO - 50mV.
> >
> > This patch
> >   - adds the scaling info flag to all channels
> >   - adds a lookup table with max reference voltage per channel
> >     (where the fixed pre-dividers apply)
> >   - allows to read the scaling attribute (computed from the Vref)
> >
> > Signed-off-by: Hector Palacios <hector.palacios@xxxxxxxx>
> > ---
> >   drivers/staging/iio/adc/mxs-lradc.c | 122
> > +++++++++++++++++++++++++++--------- 1 file changed, 93 insertions(+), 29
> > deletions(-)
> >
> > diff --git a/drivers/staging/iio/adc/mxs-lradc.c
> > b/drivers/staging/iio/adc/mxs-lradc.c index d65a594..012c42e 100644
> > --- a/drivers/staging/iio/adc/mxs-lradc.c
> > +++ b/drivers/staging/iio/adc/mxs-lradc.c
> > @@ -107,19 +107,63 @@ static const char * const mx28_lradc_irq_names[] = {
> >   	"mxs-lradc-button1",
> >   };
> >
> > +/*
> > + * Max reference voltage (mV) for each channel
> > + */
> > +static const int mx23_vref_mv[LRADC_MAX_TOTAL_CHANS] = {
> > +	1850,		/* CH0 */
> > +	1850,		/* CH1 */
> > +	1850,		/* CH2 */
> > +	1850,		/* CH3 */
> > +	1850,		/* CH4 */
> > +	1850,		/* CH5 */
> > +	1850 * 2,	/* CH6 VDDIO */
> > +	1850 * 4,	/* CH7 VBATT */
> > +	1850,		/* CH8 Temp sense 0 */
> > +	1850,		/* CH9 Temp sense 1 */
> > +	1850,		/* CH10 */
> > +	1850,		/* CH11 */
> > +	1850,		/* CH12 USB_DP */
> > +	1850,		/* CH13 USB_DN */
> > +	1850,		/* CH14 VBG */
> > +	1850 * 4,	/* CH15 VDD5V */
> > +};
> > +
> > +static const int mx28_vref_mv[LRADC_MAX_TOTAL_CHANS] = {
> > +	1850,		/* CH0 */
> > +	1850,		/* CH1 */
> > +	1850,		/* CH2 */
> > +	1850,		/* CH3 */
> > +	1850,		/* CH4 */
> > +	1850,		/* CH5 */
> > +	1850,		/* CH6 */
> > +	1850 * 4,	/* CH7 VBATT */
> > +	1850,		/* CH8 Temp sense 0 */
> > +	1850,		/* CH9 Temp sense 1 */
> > +	1850 * 2,	/* CH10 VDDIO */
> > +	1850,		/* CH11 VTH */
> > +	1850 * 2,	/* CH12 VDDA */
> > +	1850,		/* CH13 VDDD */
> > +	1850,		/* CH14 VBG */
> > +	1850 * 4,	/* CH15 VDD5V */
> > +};
>
> Should the above not be in DT ?

Do you mean for example:

	lradc@80050000 {
		compatible = "fsl,imx28-lradc";
		reg = <0x80050000 0x2000>;
		interrupts = <10 14 15 16 17 18 19
				20 21 22 23 24 25>;
		vref = <1850 1850 1850 1850
			1850 1850 1850 7400
			1850 1850 3700 1850
			3700 1850 1850 7400>
	};

I'm ok with it, but are there other examples of driver using a similar approach?
I see for example the spear-adc which reads:

	Optional properties:
	- vref-external: External voltage reference in milli-volts. If omitted
	  the internal voltage reference will be used.

which makes me believe the 'internal voltage reference' is hardcoded in the driver.
More opinions?

Best regards,
--
Hector Palacios
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