fl2k_* have libusb: error [op_dev_mem_alloc] alloc dev mem failed errno 12

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Steve Markgraf steve at steve-m.de
Tue May 1 09:51:14 UTC 2018


Hi Ignatius,

On 01.05.2018 07:16, Ignatius Rivaldi wrote:
> feanor at silmaril ~> fl2k_test -s 162e6
> Using 6 zero-copy buffers
> libusb: error [op_dev_mem_alloc] alloc dev mem failed errno 12
> Failed to allocate zero-copy buffer for transfer 4

The lib will try to allocate contiguous device memory from the Kernel
through libusb, this may fail for various reasons (not enough contiguous
DMA-capable memory because CONFIG_CMA_SIZE_MBYTES is set too low etc).

However, osmo-fl2k falls back to buffers in userspace should the
zero-copy buffer allocation fail, so no need to worry here.

> real sample rate: 15372775 current PPM: -905106 cumulative PPM: -905106

>From the output above it seems that your FL2000 device is connected to a
USB 2.0 port, so it only can achieve 14-15 MS/s. You need a USB 3.0 port
for higher rates.

> then when I try to connect red and ground output to oscilloscope,
> there is no output at all, even if I use fl2k_fm

Yes, if the sample rate  the host can supply does not match the PLL
frequency of the FL2000, the line buffer in the chip will underrun and
then there is no output anymore until re-initializing the device.

Regards,
Steve



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