Transceiver52M: Update to UHD streamer interface

This patch is long overdue and can now be merged after better understanding
of timestamp stability issues. UHD tick / timespec conversions were
generally used with the streamer interface, though these calls are actually
independent change sets. The combination would lead to internal rounding
errors and a timing drift most notably on B100 running at GSM symbol
rate multiples. There are no known issues, however, with the streamer code
itself.

The aforementioned issue was discovered in test code only, which was never
merged to mainline.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Add UHD device type checking

UHD device type was previously detected, but only categorized in
terms of bus type, USB or Ethernet, and sample rate capability.
With the number of supported device increasing, we can no longer
easily group devices since we need to handle more and more
device-specific peculiarities. Some of these factors are managed
internally by the UHD driver, but other factors (e.g. timing
offsets) are specific to a single device.

Start by maintaining an enumerated list of relevant device types
that we can use for applying device specific operations. Also
rename the USB/Ethernet grouping to transmit window type because
that's what it is.

enum uhd_dev_type {
        USRP1,
        USRP2,
        B100,
        NUM_USRP_TYPES,
};

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Add device offset correction table

Previously, two timing correction values were used for UHD devices
depending on the sample rate of 270.833e3 or 400e3 for native GSM or
resampled device rate respectively. The correction values compensate
for residual timing effects due to analog component delays, filters
lag times, and general fudge factors. These values are device
specific and over-generalized by the two value configuration.

This patch adds the following struct to store these correction
values by device type and sample rate - through samples-per-symbol.

struct uhd_dev_offset {
        enum uhd_dev_type type;
        int sps;
        double offset;
};

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Remove periodic alignment update from UHD build

Periodic timing alignment should never be required for UHD devices,
though the mechanism was used as a fallback mechanism should UHD
not properly recover after an underrun - as may occur in old
003.003.000 based revisions. This issue is not a concern in more
recent UHD releases and deprecates this code for legacy USRP1
use only.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Remove and rename oversampling variables

The transceiver only uses a single integer oversampling value,
which is more simply referred to as samples-per-symbol.

mRadioOversampling --> mSPS
mTransceiverOversampling (removed)

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Set sample rate from within the radio device

The GSM transceiver only operates at a whole number multiple of
the GSM rate and doesn't care about the actual device rate and
if resampling is used. Therefore GSM specific portion of the
transceiver should only need to submit the samples-per-symbol
value to the device interface.

Then, the device should be able to determine the appropriate
sample rate (400 ksps or 270.833 ksps) and if resampling is
appropriate.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Set resampling option automatically based on device

Remove the built time resampling selection and link both options.
Move the normal push/pullBuffer() calls back to the base class and
overload them in the inherited resampling class.

USRP2/N2xx devices are the only devices that require resampling so
return that resampling is necessary on the device open(), which is
the point at which the device type will be known.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Allow tolerance in UHD sample rate selection

We're performance floating point comparisons so allow a
10 Hz offset when UHD does not return an exact sample rate;

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Use exception blocks for rate changes

UHD will throw if something goes awry in these sensitive sections,
so we should catch and shutdown gracefully. There is no recovery
if we can't set rates.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Explicitly check for USRP2 device type

Before, we assumed that non-B100 device was implicitly a USRP2
(inclusive of N200/N210). Make the check explicit so that any
unknown device will causes an error and exit.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Remove unused test code from main

The commented out test code is not maintained and behaviour is
unknown. Remove for clarity.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Verify global config sanity before using

The configuration table is instantiated as a global variable with
no means to check constructor status. This means various types
of database failure conditions (e.g. file existence, permissions,
etc.) are not reported. This patch performs a small number of
checks to make sure that the configuration is sane.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Remove redundant file existence check
Transceiver52M: Add SSE optimized convolution

Perform compile time architecture detection and selection. Only
Intel architectures are supported and tested for now.

Signed-off-by: Thomas Tsou <tom@tsou.cc>