Zynq(zedboard) Linux Software Resetting Programmable Logic alone

Question

Hi Community,
I am working with the Digilent Zedboard .
I am trying to software reset the whole programmable logic(which uses FCLK_RESET0_N) from Linux.
I found that we can do it through the SLCR(System Level control Registers) and found slcr.c Platform driver(in linux-xlnx/arch/arm/mach-zynq) precompiled in the kernel which has xslcr_reset_periph() function to reset a peripheral.
I can see an entry  for the slcr in the device tree and also see it in
/sys/class/xslcr_reset/fpga0_out
 /sys/devices/amba.0/f8000000.ps7-slcr/xslcr_reset/fpga0_out/
I dont seem to have an entry in /dev  though
How do I use this driver to perform a reset?  Can I do it with a simple 'echo ' as shown for the power management driver in http://www.wiki.xilinx.com/Zynq+Power+Management ?
echo enabled > /sys/devices/amba.0/e0001000.serial/tty/ttyPS0/power
echo (rising|falling|both) > /sys/class/gpio/gpio<n>/edge
or Do I need to write a character device driver that communicates to the platform driver for this? ..Thanks in advance !

Answer 1

I agree with this completely.  The functionality is there, and it seems silly to burn a GPIO pin to recreate it.
The base address to the SLCRs (according to the slcr definition in my devicetree, check yours for 'ps7-slcr') is 0xf80000.  According to slcr.c, the offset for the FPGA reset lines 0x240.  This gives you some options. 
Here are 3 ways to do what you'd like:
1) /sbin/devmem 0xf8000240 32 0xF // resets ALL lines, 0x1 is RESET0, 0x2 RESET1 0x3 RESET0+RESET1
Be sure to write 0xf8000240 to 0x0 to bring it out of reset!
2) mmap /dev/mem and write it in C
3) (untested) change the devicetree "compatible" property to include "uio_pdrv_genirq" with a fake IRQ or modify uio_pdrv.c to read the compatible property.  In either case, this lets you use the UIO system to access these registers from userspace (see http://fpgacpu.wordpress.com/2013/05/28/how-to-design-and-access-a-memory-mapped-device-part-two/).
Keep in mind that, at least with 14.7 kernel, you DO NOT need to recompile your kernel unless you modify uio_pdrv.c  If you use the "fake" IRQ solution, it already comes in the stock kernel.
Hope this helps!