> On Oct 24, 2016, at 11:01 PM, John Syne <john3...@gmail.com> wrote: > >> >> On Oct 24, 2016, at 10:52 PM, Mugunthan V N <mugunthan...@ti.com> wrote: >> >> On Tuesday 25 October 2016 02:28 AM, John Syne wrote: >>>>> On Oct 23, 2016, at 11:02 PM, Mugunthan V N <mugunthan...@ti.com> 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 <mugunthan...@ti.com> >>>>> --- >>>>> >>>>> 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? > I was thinking that if you are using this driver as an ADC, you may want the > flexibility to make these changes in the DT. I’m doing this by connecting > sensors to the ADC inputs. I’m not using this driver for a touchscreen.
Here is a DT overlay were this gets using on the BeagleBoneBlack. https://github.com/RobertCNelson/bb.org-overlays/blob/master/src/arm/BB-ADC-00A0.dts Besides, these DT features are already implemented in the driver so it is just a matter of adding these entries to the am33xx.dtsi & am4372.dtsi, which you modified in this patch series. Regards, John > > Regards, > John >> >> Regards >> Mugunthan V N
