On Mon, 24 Oct 2016, John Syne wrote: > > 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.
This looks like configuration, no? DT should be used to describe the hardware. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
