> On Oct 23, 2016, at 11:02 PM, Mugunthan V N <mugunthanvnm@xxxxxx> wrote: > > Increase ADC reference clock from 3MHz to 24MHz so that the > sampling rates goes up from 100K samples per second to 800K > samples per second on AM335x and AM437x SoC. > > Also increase opendelay for touchscreen configuration to > equalize the increase in ADC reference clock frequency, > which results in the same amount touch events reported via > evtest on AM335x GP EVM. > > Signed-off-by: Mugunthan V N <mugunthanvnm@xxxxxx> > --- > > This patch depends on ADC DMA patch series [1] > > Without DMA support, when ADC ref clock is set at 24MHz, I am > seeing fifo overflow as CPU is not able to pull the ADC samples. > This answers that DMA support is must for ADC to consume the > samples generated at 24MHz with no open, step delay or > averaging with patch [2]. > > Measured the performance with the iio_generic_buffer with the > patch [3] applied > > [1] - http://www.spinics.net/lists/devicetree/msg145045.html > [2] - http://pastebin.ubuntu.com/23357935/ > [3] - http://pastebin.ubuntu.com/23357939/ > > --- > include/linux/mfd/ti_am335x_tscadc.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h > index b9a53e0..96c4207 100644 > --- a/include/linux/mfd/ti_am335x_tscadc.h > +++ b/include/linux/mfd/ti_am335x_tscadc.h > @@ -90,7 +90,7 @@ > /* Delay register */ > #define STEPDELAY_OPEN_MASK (0x3FFFF << 0) > #define STEPDELAY_OPEN(val) ((val) << 0) > -#define STEPCONFIG_OPENDLY STEPDELAY_OPEN(0x098) Wouldn’t this be better to add this to the devicetree? ti,chan-step-avg = <0x16 0x16 0x16 0x16 0x16 0x16 0x16>; ti,chan-step-opendelay = <0x500 0x500 0x500 0x500 0x500 0x500 0x500>; ti,chan-step-sampledelay = <0x0 0x0 0x0 0x0 0x0 0x0 0x0>; Regards, John > +#define STEPCONFIG_OPENDLY STEPDELAY_OPEN(0x500) > #define STEPDELAY_SAMPLE_MASK (0xFF << 24) > #define STEPDELAY_SAMPLE(val) ((val) << 24) > #define STEPCONFIG_SAMPLEDLY STEPDELAY_SAMPLE(0) > @@ -137,7 +137,7 @@ > #define SEQ_STATUS BIT(5) > #define CHARGE_STEP 0x11 > > -#define ADC_CLK 3000000 > +#define ADC_CLK 24000000 > #define TOTAL_STEPS 16 > #define TOTAL_CHANNELS 8 > #define FIFO1_THRESHOLD 19 > -- > 2.10.1.502.g6598894 > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
