On Fri, 8 Dec 2017 18:41:45 +0100 Stefan Brüns <stefan.bruens@xxxxxxxxxxxxxx> wrote: > Currently, the INA2xx driver may end up causing 100% load on a single core > and fully loading the I2C bus, which is caused by two different issues: > > The code uses a udelay to bridge the gab between two subsequent samples. > As the sampling interval may be up to 16 seconds, the CPU is busy > waiting most of the time. > > The second issue manifests when using the (default) "synchronous" mode. > The code polls for a set conversion ready flag, but fails to align the > sampling interval to the raising flag. The polling interval is > (rightfully) slighly shorter than the sampling interval, so after some > samples the sampling thread is continously polling. I'm confused. Would you mind doing an asci art example perhaps? Thanks, Jonathan > > The patch series fixes both issues: > Patch 1 and 2 are just some small cosmetic changes. > > Patch 3 removes an unnecessary read. According to the datasheet, the > CNVR flag is only cleared by reading the power register, but is cleared > by reading any of the measurement registers, thus the dummy read can > be skipped. This behaviour has been confirmed by TI technical support. > > Patch 4 replaces the udelay with usleep_range. > > Patch 5 reworks the delay logic. Previously the IIO timestamp clock was > used to capture entry and exit times of the work function. The > timestamp clock is user selectable and may be non-monotonic. Also, > any time spent outside the work function is not accounted for. > > Patch 6 moves the timestap capture to the end of the conversion ready > status poll. > > Patch 7 addresses the alignment issue. Every time an unset flag is seen > on poll loop entry, the reference timestamp is readjusted. > > Both old and fixed behaviour has been verified using a logic analyzer. > In synchrounous mode, every few samples a double read of the status > register can be observed, showing the raising status flag, the other > samples are evenly spaced at sampling intervals inbetween. > > > Stefan Brüns (7): > iio: adc: ina2xx: Remove bogus cast for data argument > iio: adc: ina2xx: Clarify size requirement for data buffer > iio: adc: ina2xx: Remove unneeded dummy read to clear CNVR flag > iio: adc: ina2xx: Do not udelay for several seconds > iio: adc: ina2xx: Use a monotonic clock for delay calculation > iio: adc: ina2xx: Align timestamp with conversion ready flag > iio: adc: ina2xx: Actually align the loop with the conversion ready > flag > > drivers/iio/adc/ina2xx-adc.c | 104 ++++++++++++++++++++++++------------------- > 1 file changed, 59 insertions(+), 45 deletions(-) > -- 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
