[PATCH] iio: adc: xilinx-xadc: Convert to raw spinlock

[Sebastian Andrzej Siewior]

* Xander Huff | 2015-05-14 17:45:04 [-0500]:

>With no other processes running, I got the following results after a
>couple of hours on one of our devices:
>
>admin at Xander-roboRIO:~# cyclictest -S -m -p 98
># /dev/cpu_dma_latency set to 0us
>policy: fifo: loadavg: 0.01 0.07 0.12 1/176 1473
>
>T: 0 ( 1373) P:98 I:1000 C:6503872 Min:      9 Act:   13 Avg:   13 Max:      51
>T: 1 ( 1374) P:98 I:1500 C:4335914 Min:      9 Act:   12 Avg:   13 Max:      49
>
>With a VI reading all default handles (raw, offset, scale,
>sampling_frequency) in /sys/bus/iio/devices/iio:device0 constantly in
>a while loop, I got the following results after a couple hours on the
>same device:
>
>admin at Xander-roboRIO:~# cyclictest -S -m -p 98
># /dev/cpu_dma_latency set to 0us
>policy: fifo: loadavg: 6.93 7.30 7.47 3/182 1530
>
>T: 0 ( 1487) P:98 I:1000 C:4497008 Min:     11 Act:   20 Avg:   21 Max:      69
>T: 1 ( 1488) P:98 I:1500 C:2998005 Min:     11 Act:   20 Avg:   22 Max:      59

So there is an increase. And there is even a for-loop and I don't know
how deep it is nested. Anyway, do you think it is worth it or would it
be better to get rid of the raw-locks and simply push everything into
threaded context?

Sebastian