XAPP1251 - UIO mmap() fails

[theultimatesource]

- IP, Version: AXI JTAG, 1.0
- Vivado, SDK, Petalinux: 2017.4
- Device:      Zynq-7000

hello,

I am trying to recreate XAPP1251. It is made with Vivado design tools 2014.3.1. It is a reference design for XVCServer using JTAG over ethernet.

Following chapter "Connect Hardware", step 4 I am running the application on the target with the following message:

xvcmod login: root
Password:
root@xvcmod:~# xvcServer &
[1] 1276
MMAP Failed

Test case

(1) the periferal is listed as /dev/ui0
(2) the contents of /sys/class/uio/ui0/maps/map0/ are correct (address, size, offset)
(3) stepping through the code in SDK:

   fd_uio = open("/dev/uio0", O_RDWR );
   if (fd_uio < 1) {
      fprintf(stderr,"Failed to Open UIO Device\n");
      return -1;
   }

   s = socket(AF_INET, SOCK_STREAM, 0);

   if (s < 0) {
      perror("socket");
      return 1;
   }

   volatile jtag_t* ptr = (volatile jtag_t*) mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
                    fd_uio, 0);
   if (ptr == MAP_FAILED)
                fprintf(stderr, "MMAP Failed\n");

   close(fd_uio);

I am able to open uio0 successfully and creating a socket. It fails to mmap fd_uio.
jtag_t is defined as:

typedef struct {
  uint32_t  length_offset;
  uint32_t  tms_offset;
  uint32_t  tdi_offset;
  uint32_t  tdo_offset;
  uint32_t  ctrl_offset;
} jtag_t;

It's fields are not getting assigned any values after calling mmap().

Can someone give me further hints on solving this issue, thank you.

[wittich]

Hi, your message from your first printout suggests that the open call is failing, not the mmap?

[theultimatesource]

Uh, yes, I am sorry,

That first printout is outdated, I solved that problem (copy and pasted the wrong text from my document). I edited my question.

[wittich]

Hmmm, I don't have any additional ideas. Have you looked at errno?

Edit: as a (probably not very useful) piece of information: 

Using Vivado/Petalinux 2017.2 I was able to get a virtual cable server to work in a system that sounds very similar to what you have, except for the problem discussed and solved here: socket problem

I am showing below the kernel configuration and the contents of the sysfs entries, in case that is useful to you.

root@yugevu2:~# zcat /proc/config.gz  | grep -i UIO
CONFIG_UIO=y
# CONFIG_UIO_CIF is not set
CONFIG_UIO_PDRV_GENIRQ=y
CONFIG_UIO_DMEM_GENIRQ=y
# CONFIG_UIO_AEC is not set
# CONFIG_UIO_SERCOS3 is not set
# CONFIG_UIO_PCI_GENERIC is not set
# CONFIG_UIO_NETX is not set
# CONFIG_UIO_PRUSS is not set
# CONFIG_UIO_MF624 is not set
CONFIG_UIO_XILINX_APM=y

root@yugevu2:~# ls /sys/class/uio/uio0/maps/map0/
addr    name    offset  size
root@yugevu2:~# cat /sys/class/uio/uio0/maps/map0/*
0x40050000
/amba_pl/axi_jtag_v1_0@40050000
0x0
0x00010000

In my notes from that I found that the following two things were needed beyond what's in the XAPP1251, both in the device tree, due to kernel changes in the UIO driver. The first passes a choice to the UIO driver, the second is needed for mapping the AXI jtag to the kernel. However, I think in my case these were needed to get /dev/uio0 to be created _at all_ so this is probably not of use to you.

/{
  chosen {
          bootargs = "console=ttyPS0,115200 earlyprintk root=/dev/mmcblk0p2 rw rootwait uio_pdrv_genirq.of_id=\"generic-uio\"";
  };
};

// virtual cable
&axi_jtag {
    compatible = "generic-uio";
};

[stephenm · Accepted solution]

Can you manually set the MAP_SIZE here to 4096:

mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
fd_uio, 0);

For example:
mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED,
fd_uio, 0);