Hi, all, what I want to do is the following:
There is a LinearTechnology/AD LTC2500-32 ADC that can deliver up to 1Meg 32-Bit results per second on its slave SPI-Interface. Baud rate can be 100MBit/sec. I could live with somewhat less, but would like to max it out as far as possible. I want to read the data via SPI0. Collecting them by DMA might be possible, but I see problems allocating large enough fixed buffers and much ado with physical/virtual adresses. So I decided to use the PRU0 to do the fast work. In the 12 KB shared ram, there will be 2 1KWord ping-pong-Buffers and a few words for command/status/handshake. The PRU can simply do busy waiting; it has nothing else to do. No interrupts etc needed. The ARM CPU fetches 1Kword worth of data when a buffer gets full and moves it to virtual address land, where there is a lot of space & network access. I can mmap() the shared buffer, the PRU data rams and the PRU instruction rams and change / test them. (I cannot yet load the PRU program & start it, but that is not the problem now.) The problem is that I get bus errors when I access anything of the SPI interface. There was some "Robotics" driver pre-installed that claimed all SPI for itself, which I consider kinda unfriendly. Blacklisting removed it, but it did not remove the bus errors. What is the minimum I have to do to get access to the SPI registers? I get no complaints when I mmap() the SPI0, but I get killed when I actually access it. Using devmem2 does the same. ------------------------------ root@beaglebone:/home/gerhard# devmem2 0x48030000 Bus error All existing SPI examples end with "now look at the slot entries...." but kernel overlays are gone and going through the file system is MUCH too slow. I could live with a userland wart, I need nothing with interrupts or a nice & tidy device driver. At least for now. ------------------------- root@beaglebone:/home/gerhard# inxi -v7 System: Host: beaglebone Kernel: 4.9.82-ti-r102 armv7l (32 bit gcc: 6.3.0) Console: tty 0 Distro: Debian GNU/Linux 9 (stretch) ..... ------------------------- root@beaglebone:/home/gerhard# lsmod Module Size Used by pruss_soc_bus 4788 0 evdev 13811 1 uio_pdrv_genirq 4205 0 uio 11036 1 uio_pdrv_genirq 8021q 24278 0 garp 7357 1 8021q mrp 9301 1 8021q stp 2686 1 garp llc 6287 2 garp,stp usb_f_mass_storage 51462 2 usb_f_acm 8610 2 u_serial 13482 3 usb_f_acm usb_f_ecm 11619 2 usb_f_rndis 26944 2 u_ether 13962 2 usb_f_ecm,usb_f_rndis libcomposite 55456 16 usb_f_ecm,usb_f_acm,usb_f_mass_storage,usb_f_rndis iptable_nat 2512 0 nf_conntrack_ipv4 12035 1 nf_defrag_ipv4 2016 1 nf_conntrack_ipv4 nf_nat_ipv4 6857 1 iptable_nat nf_nat 18928 1 nf_nat_ipv4 nf_conntrack 117486 3 nf_conntrack_ipv4,nf_nat_ipv4,nf_nat iptable_mangle 2303 0 iptable_filter 2453 0 pru_rproc 14966 0 pruss_intc 9092 1 pru_rproc pruss 10889 1 pru_rproc tieqep 9111 0 ip_tables 14529 3 iptable_mangle,iptable_filter,iptable_nat x_tables 22165 3 iptable_mangle,ip_tables,iptable_filter So, to repeat my question: What is the minimum I have to do to get access to the SPI registers? thanks and best regards, Gerhard -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/fed54861-d6f9-45dd-b2f1-7b9de005ab10%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
