HS38x2 Linux, buildroot, how-to-activate UIO driver.

[joshualin-petaio]

Hi export,
Can you help how to activate UIO driver in buildroot?
Thanks, Joshua.

[EvgeniiDidin]

Hi Joshua,

Further instructions implies that buildroot was somehow configured(with kernel enabled) and built.
There are three steps how-to enable UIO driver in buildroot:
1) Enable UIO in kernel.
In terminal in buildroot directory run "make linux-menuconfig". This command will open configuration menu for Linux kernel.
After opening press "/" button and enter "uio" in a search field:

Press "1" and enable UIO by pressing "y". Also enter UIO driver submenu and enable next options:

Save and exit menu.

2) Specifying UIO regions in .dts file.
In order of specifying UIO regions it is necessary to modify .dts file.
To find out which .dts file is used in buildroot configuration please run "make menuconfig" in buildroot root directory.
Go to "Kernel" menu and the name of .dts file is defined by next field:

In configuration from the picture above the .dts file is "hsdk.dts"

Next open specified by your configuration .dts file in the following directory:

The UIO section should be specify in subsection where IO devices are defined, in case of hsdk.dts UIO section should be located in soc subsection:

The full contents of the file from picture above can be found here: https://elixir.bootlin.com/linux/latest/source/arch/arc/boot/dts/hsdk.dts

The UIO section example:

uioEV: uio@0 {
compatible = "generic-uio";      /* NOTE!!! value should be the same in boot command, see "step 3" */
 reg = < 0x0 0xffff0000 0x0 0x4000        /* 4KiB */            /*  for arconnect*/
         0x0 0x20000000 0x0 0x10000000    /* 256 MiB */    /*  for shared data */
         0x0 0x10000000 0x0 0x08000000>;  /* 128 MiB */   /* for code */
/* It is possible to create more UIO regions if necessary */
 reg-names = "arconnect", 
             "ev_shared_mem",
             "ev_code_mem";
interrupt-parent = <&idu_intc>; 
interrupts = < 7 1 >; };  /* interrupt line #7 */

3) Enabling UIO in Kernel boot command.
It is also necessary to enable UIO in Kernel boot command. The boot command is located in the .dts file described in step 2. E.g. bootargs line in hsdk.dts:

bootargs = "earlycon=uart8250,mmio32,0xf0005000,115200n8 console=ttyS0,115200n8 debug print-fatal-signals=1";

Please add a uio_pdrv_genirq.of_id=generic-uio substring in the end of the string, the line should be like:

bootargs = "earlycon=uart8250,mmio32,0xf0005000,115200n8 console=ttyS0,115200n8 debug print-fatal-signals=1 uio_pdrv_genirq.of_id=generic-uio";

Note!!! The value in uio_pdrv_genirq.of_id=generic-uio should be the same as compatible field in UIO section in step 2.

Rebuilding kernel in buildroot
After doing all modification just run "make" in buildroot root directory, it will rebuild kernel once. If more changes in .dts or kernel code were performed run "make linux-menuconfig" then exit the menu, this will trigger buildroot to rebuild Kernel on next "make run". Commonly buildroot is not rebuilding packages which were already built.

Verifying UIO in runtime
Once image is built and booted to verify that UIO regions are available go to /sys/bus/platform/devices/xxx.uio/ directory. If everything is correct, the directory uio0 with maps[0,1,2,...](maps = regions defined in .dts) directories inside should appear.

Please leave a comment in this issue if you face any issues.

Best regards,
Evgeniy

[joshualin-petaio]

Hi Evgeniy,

I can find 0.uio in /sys/bus/platform/devices/xxx.uio/
But can't find maps in /dev/
Do you know why ?

BR,
Joshua

[EvgeniiDidin]

Hi Joshua,

Missing "/dev/uio0" and "maps" directory means that UIO is not working properly. Could you please search for "uio" messages in dmesg output and share the result of the search?
Here is the result of the search from dmesg from the system with working uio:

# dmesg | grep -i uio
Kernel command line: earlycon=uart8250,mmio32,0xf0005000,115200n8 console=ttyS0,115200n8 debug print-fatal-signals=1 uio_pdrv_genirq.of_id=generic-uio
uio_pdrv_genirq ffff0000.uio: use noncoherent DMA ops

Best regards,
Evgeniy

[joshualin-petaio]

Hi Evgeniy,

following is my dmesg content :

Best regards,
Joshua

[joshualin-petaio]

Hi Evgeniy,

When I change the some setting in buildroot from success case like enable BR2_ARC_ATOMIC_EXT, uclibc -> glibc, enable c++.
It will run linux image fail after downloading.
Can you help me to check it ?
Attach include buildroot .config, linux .config, linux massage.
linux_image_setting_and_log.zip

Thanks, Joshua

[EvgeniiDidin]

Hi Joshua,

I took a look in the boot log and found that Kernel was built against uclibc toolchain:

Linux version 5.10.80 (joshua@localhost.localdomain) (arc-linux-gcc (ARCv2 ISA Linux uClibc toolchain - build 965) 11.2.0, GNU ld (ARCv2 ISA Linux uClibc toolchain - build 965) 2.37) #11 SMP PREEMPT Thu Mar 31 04:58:58 EDT 2022

At the same time buildroot was configured to use Glibc toolchain.
This discrepancy may cause the error you have observed.

Please try to do a proper clean in Linux kernel directory and rebuild the image.
You can clean with next command:

make clean

Best regards,
Evgeniy Didin

[joshualin-petaio]

Hi Evgeniy,
I change to use glibc.
But it still has this issue.
dump log is here.
minicom.txt

Thanks, Joshua

[joshualin-petaio]

Hi Evgeniy,

In order to put files in to linux image, I try to use option BR2_ROOTFS_OVERLAY in buildroot.
I can see the files are in the /buildroot-dir/output/images/rootfs.tar, but I can't see them after download vmlinux.
Do you know how to run this correctly ?

Thanks, Joshua

[joshualin-petaio]

Hi Evgeniy,

I found that files can't put in /tmp/ folder.
When I put them to /usr/, I can see then after download vmlinux.

Thanks, Joshua

[joshualin-petaio]

Hi Evgeniy,

When I run openamp host application after download vmlinux.
It shows LIB not found.
"# ./echo_test
./echo_test: error while loading shared libraries: liblibsysfs.so: cannot open shared object file: No such file or directory "
And I try to enable option "BR2_PACKAGE_LIBSYSFS" in buildroot, but it still show this error.
Do you know how to enable libsysfs correctly ?

Thanks, Joshua

[joshualin-petaio]

Hi Evgeniy,

I found the linux seems not enable data cache.
But we need enable data cache for non-dword alignment address access.
Because our HW bus only support DW alignment.
So we need use cache region for non-DW alignment address access.
And with cache coherency mechanism for openamp.
Do you know how to enable data cache in linux ?

Thanks, Joshua

[joshualin-petaio]

Hi Evgeniy,

Some information update.
Some ARConnect region can't write but some region can.
The 0xaf000000 is can't.
But 0xaf000104 is can. (arconnect cmd address)

Thanks, Joshua