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) +#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
