I have the same error message running a standard ubuntu kernel 4.15.0-21-generic with 16 GB RAM. I'm not familiar with setting the right kernel options. My config file for the kernel just shows: CONFIG_CMA=y # CONFIG_CMA_DEBUG is not set # CONFIG_CMA_DEBUGFS is not set CONFIG_CMA_AREAS=7 I haven't been able to receive a FM signal yet. My output from the fl2k_test shows: sudo fl2k_test -s 162e6 Allocating 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 Falling back to buffers in userspace Reporting PPM error measurement every 10 seconds... Press ^C after a few minutes. real sample rate: 113962068 current PPM: -296530 cumulative PPM: -296530 real sample rate: 113975309 current PPM: -296449 cumulative PPM: -296489 real sample rate: 114139355 current PPM: -295436 cumulative PPM: -296136 Do I need to change my kernel settings or will the device simply won't work?

Hi, On 30.05.2018 17:57, Hannes Wagner wrote: What are the commandline parameters you are using for fl2k_fm? As you can see below, you need to limit your samplerate to < 114 MS/s. What happens according to the output: libfl2k is running on a system that seems to support zero-copy transfers, but fails during allocation. Probably there is not enough DMA-able contiguous memory present for the Kernel. This is no big deal, as libfl2k will then de-allocate the already allocated zero-copy buffers, and then fall back to buffers allocated with malloc() (which of course then will require copy_from_user() in the Kernel). So it should work just fine, you just won't get the performance benefit of zero-copy buffers. And according to the output of fl2k_test, you are getting around 114 MS/s, as you are probably using a Renesas uPD7202xx controller. If you want to generate any output, you need to set the sample rate to a value below that. Regards, Steve