On 29/10/2020 14:18, Ian Abbott wrote:
Commit eddd2a4c675c ("staging: comedi: cb_pcidas: refactor
write_calibration_bitstream()") inadvertently removed one of the
`udelay(1)` calls when writing to the calibration register in
`cb_pcidas_calib_write()`. Reinstate the delay. It may seem strange
that the delay is placed before the register write, but this function is
called in a loop so the extra delay can make a difference.
This _might_ solve reported issues reading analog inputs on a
PCIe-DAS1602/16 card where the analog input values "were scaled in a
strange way that didn't make sense". On the same hardware running a
system with a 3.13 kernel, and then a system with a 4.4 kernel, but with
the same application software, the system with the 3.13 kernel was fine,
but the one with the 4.4 kernel exhibited the problem. Of the 90
changes to the driver between those kernel versions, this change looked
like the most likely culprit.
Actually, I've realized that this patch will have no effect on the
PCIe-DAS1602/16 card because it uses a different driver - cb_pcimdas,
not cb_pcidas.
Greg, you might as well drop this patch if you haven't already applied
it, since it was only a hunch that it fixed a problem.
--
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