On Tuesday 25 October 2016 02:28 AM, John Syne wrote: >> > 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>; For a touch screen, there is not need to change in these parameter settings, so my opinion is to keep it as is. Or am I missing something? Regards Mugunthan V N -- 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
