Re: [PATCH 2/2] iio: adc: ti_am335x_tscadc: Improve accuracy of measurement
On Sat, 01 Dec 2018, Jonathan Cameron wrote: > On Wed, 28 Nov 2018 09:14:32 + > Lee Jones wrote: > > > On Mon, 19 Nov 2018, Vignesh R wrote: > > > > > When performing single ended measurements with TSCADC, its recommended > > > to set negative input (SEL_INM_SWC_3_0) of ADC step to ADC's VREFN in the > > > corresponding STEP_CONFIGx register. > > > Also, the positive(SEL_RFP_SWC_2_0) and negative(SEL_RFM_SWC_1_0) > > > reference voltage for ADC step needs to be set to VREFP and VREFN > > > respectively in STEP_CONFIGx register. > > > Without these changes, there may be variation of as much as ~2% in the > > > ADC's digital output which is bad for precise measurement. > > > > > > Signed-off-by: Vignesh R > > > --- > > > drivers/iio/adc/ti_am335x_adc.c | 5 - > > > > > include/linux/mfd/ti_am335x_tscadc.h | 4 > > > > Acked-by: Lee Jones > > > I'll leave this for v2 given changes in the first patch. > > My assumption is at the moment that both will go through mfd. > Shout Lee if you have other plans. I'm fine with that. -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
Re: [PATCH 2/2] iio: adc: ti_am335x_tscadc: Improve accuracy of measurement
On Wed, 28 Nov 2018 09:14:32 + Lee Jones wrote: > On Mon, 19 Nov 2018, Vignesh R wrote: > > > When performing single ended measurements with TSCADC, its recommended > > to set negative input (SEL_INM_SWC_3_0) of ADC step to ADC's VREFN in the > > corresponding STEP_CONFIGx register. > > Also, the positive(SEL_RFP_SWC_2_0) and negative(SEL_RFM_SWC_1_0) > > reference voltage for ADC step needs to be set to VREFP and VREFN > > respectively in STEP_CONFIGx register. > > Without these changes, there may be variation of as much as ~2% in the > > ADC's digital output which is bad for precise measurement. > > > > Signed-off-by: Vignesh R > > --- > > drivers/iio/adc/ti_am335x_adc.c | 5 - > > > include/linux/mfd/ti_am335x_tscadc.h | 4 > > Acked-by: Lee Jones > I'll leave this for v2 given changes in the first patch. My assumption is at the moment that both will go through mfd. Shout Lee if you have other plans. Jonathan
Re: [PATCH 2/2] iio: adc: ti_am335x_tscadc: Improve accuracy of measurement
On Mon, 19 Nov 2018, Vignesh R wrote: > When performing single ended measurements with TSCADC, its recommended > to set negative input (SEL_INM_SWC_3_0) of ADC step to ADC's VREFN in the > corresponding STEP_CONFIGx register. > Also, the positive(SEL_RFP_SWC_2_0) and negative(SEL_RFM_SWC_1_0) > reference voltage for ADC step needs to be set to VREFP and VREFN > respectively in STEP_CONFIGx register. > Without these changes, there may be variation of as much as ~2% in the > ADC's digital output which is bad for precise measurement. > > Signed-off-by: Vignesh R > --- > drivers/iio/adc/ti_am335x_adc.c | 5 - > include/linux/mfd/ti_am335x_tscadc.h | 4 Acked-by: Lee Jones -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
Re: [PATCH 2/2] iio: adc: ti_am335x_tscadc: Improve accuracy of measurement
On Mon, 19 Nov 2018 12:12:36 +0530
Vignesh R wrote:
> When performing single ended measurements with TSCADC, its recommended
> to set negative input (SEL_INM_SWC_3_0) of ADC step to ADC's VREFN in the
> corresponding STEP_CONFIGx register.
> Also, the positive(SEL_RFP_SWC_2_0) and negative(SEL_RFM_SWC_1_0)
> reference voltage for ADC step needs to be set to VREFP and VREFN
> respectively in STEP_CONFIGx register.
> Without these changes, there may be variation of as much as ~2% in the
> ADC's digital output which is bad for precise measurement.
>
> Signed-off-by: Vignesh R
Given the header changes in mfd and the fact not much is going on with this
driver in IIO at the moment, I'm happy for this to go through the mfd tree.
Acked-by: Jonathan Cameron
Thanks,
Jonathan
> ---
> drivers/iio/adc/ti_am335x_adc.c | 5 -
> include/linux/mfd/ti_am335x_tscadc.h | 4
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
> index cafb1dcadc48..9d984f2a8ba7 100644
> --- a/drivers/iio/adc/ti_am335x_adc.c
> +++ b/drivers/iio/adc/ti_am335x_adc.c
> @@ -142,7 +142,10 @@ static void tiadc_step_config(struct iio_dev *indio_dev)
> stepconfig |= STEPCONFIG_MODE_SWCNT;
>
> tiadc_writel(adc_dev, REG_STEPCONFIG(steps),
> - stepconfig | STEPCONFIG_INP(chan));
> + stepconfig | STEPCONFIG_INP(chan) |
> + STEPCONFIG_INM_ADCREFM |
> + STEPCONFIG_RFP_VREFP |
> + STEPCONFIG_RFM_VREFN);
>
> if (adc_dev->open_delay[i] > STEPDELAY_OPEN_MASK) {
> dev_warn(dev, "chan %d open delay truncating to
> 0x3\n",
> diff --git a/include/linux/mfd/ti_am335x_tscadc.h
> b/include/linux/mfd/ti_am335x_tscadc.h
> index b9a53e013bff..483168403ae5 100644
> --- a/include/linux/mfd/ti_am335x_tscadc.h
> +++ b/include/linux/mfd/ti_am335x_tscadc.h
> @@ -78,6 +78,8 @@
> #define STEPCONFIG_YNN BIT(8)
> #define STEPCONFIG_XNP BIT(9)
> #define STEPCONFIG_YPN BIT(10)
> +#define STEPCONFIG_RFP(val) ((val) << 12)
> +#define STEPCONFIG_RFP_VREFP (0x3 << 12)
> #define STEPCONFIG_INM_MASK (0xF << 15)
> #define STEPCONFIG_INM(val) ((val) << 15)
> #define STEPCONFIG_INM_ADCREFM STEPCONFIG_INM(8)
> @@ -86,6 +88,8 @@
> #define STEPCONFIG_INP_AN4 STEPCONFIG_INP(4)
> #define STEPCONFIG_INP_ADCREFM STEPCONFIG_INP(8)
> #define STEPCONFIG_FIFO1 BIT(26)
> +#define STEPCONFIG_RFM(val) ((val) << 23)
> +#define STEPCONFIG_RFM_VREFN (0x3 << 23)
>
> /* Delay register */
> #define STEPDELAY_OPEN_MASK (0x3 << 0)
[PATCH 2/2] iio: adc: ti_am335x_tscadc: Improve accuracy of measurement
When performing single ended measurements with TSCADC, its recommended
to set negative input (SEL_INM_SWC_3_0) of ADC step to ADC's VREFN in the
corresponding STEP_CONFIGx register.
Also, the positive(SEL_RFP_SWC_2_0) and negative(SEL_RFM_SWC_1_0)
reference voltage for ADC step needs to be set to VREFP and VREFN
respectively in STEP_CONFIGx register.
Without these changes, there may be variation of as much as ~2% in the
ADC's digital output which is bad for precise measurement.
Signed-off-by: Vignesh R
---
drivers/iio/adc/ti_am335x_adc.c | 5 -
include/linux/mfd/ti_am335x_tscadc.h | 4
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
index cafb1dcadc48..9d984f2a8ba7 100644
--- a/drivers/iio/adc/ti_am335x_adc.c
+++ b/drivers/iio/adc/ti_am335x_adc.c
@@ -142,7 +142,10 @@ static void tiadc_step_config(struct iio_dev *indio_dev)
stepconfig |= STEPCONFIG_MODE_SWCNT;
tiadc_writel(adc_dev, REG_STEPCONFIG(steps),
- stepconfig | STEPCONFIG_INP(chan));
+ stepconfig | STEPCONFIG_INP(chan) |
+ STEPCONFIG_INM_ADCREFM |
+ STEPCONFIG_RFP_VREFP |
+ STEPCONFIG_RFM_VREFN);
if (adc_dev->open_delay[i] > STEPDELAY_OPEN_MASK) {
dev_warn(dev, "chan %d open delay truncating to
0x3\n",
diff --git a/include/linux/mfd/ti_am335x_tscadc.h
b/include/linux/mfd/ti_am335x_tscadc.h
index b9a53e013bff..483168403ae5 100644
--- a/include/linux/mfd/ti_am335x_tscadc.h
+++ b/include/linux/mfd/ti_am335x_tscadc.h
@@ -78,6 +78,8 @@
#define STEPCONFIG_YNN BIT(8)
#define STEPCONFIG_XNP BIT(9)
#define STEPCONFIG_YPN BIT(10)
+#define STEPCONFIG_RFP(val)((val) << 12)
+#define STEPCONFIG_RFP_VREFP (0x3 << 12)
#define STEPCONFIG_INM_MASK(0xF << 15)
#define STEPCONFIG_INM(val)((val) << 15)
#define STEPCONFIG_INM_ADCREFM STEPCONFIG_INM(8)
@@ -86,6 +88,8 @@
#define STEPCONFIG_INP_AN4 STEPCONFIG_INP(4)
#define STEPCONFIG_INP_ADCREFM STEPCONFIG_INP(8)
#define STEPCONFIG_FIFO1 BIT(26)
+#define STEPCONFIG_RFM(val)((val) << 23)
+#define STEPCONFIG_RFM_VREFN (0x3 << 23)
/* Delay register */
#define STEPDELAY_OPEN_MASK(0x3 << 0)
--
2.19.1
