It's not your code, that should be obvious when it work in 3.8.x kernels,
and not so well on 4.x.
But the first thing that pops into my mind is that this is related to DMA.
However about pasting a full output of the error messages you're getting.
On Thu, Jan 19, 2017 at 3:41 AM, Gregor Steiner <gluasto...@gmail.com>
wrote:
> Hi,
>
> about two years ago I was running the old 3.* kernel and SPI worked fine
> for what I was doing.
> I updated to Debian 8.6 / 4.4.40-ti-r80 but now the same unchanged code
> throws odd errors that I can't figure out on my own.
>
> Here is how I'm writing out via SPI (16 bpw, mode 2)
>
> struct spi_ioc_transfer info =
> {
> .tx_buf = (unsigned long)wbuf,
> .len = length,
> };
>
> int ret = ioctl(fd, SPI_IOC_MESSAGE(1), &info);
> if (ret < 1)
> {
> printf("error: %s\n", strerror(ret));
> return 0;
> }
>
> The size of wbuf usually ranges from 10 bytes to 10000 bytes.
> It will print "error: Unknown error -1" which does not leave me with much.
>
> I also noticed that now (with the new kernel) I had to remove cs_change =
> 1 from the spi_ioc_transfer struct or else CS would stay low the whole time
> (between messages).
>
> Anyway, should I revert to 3.* or does anyone know what's going on?
>
>
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