Intel® SoC FPGA Embedded Development Suite
Support for SoC FPGA Software Development, SoC FPGA HPS Architecture, HPS SoC Boot and Configuration, Operating Systems
466 Discussions

Why Cyclon V Reset manager status register always read 0?



In our project we have u-boot v2018.11. I have been requested to write a functionality related to reset reason. Following the already implemented functionality mainly in iMX devices I wrote similar function. And read values from the register is always 0! Why? This is my code:


static struct socfpga_reset_manager *reset_manager_base =

       (struct socfpga_reset_manager *)SOCFPGA_RSTMGR_ADDRESS;   

u32 cause;

cause = readl(&reset_manager_base->status) & 0xFFFFF;


I thought it could be related to incorrect access to the register. In Cyclon V HPS TRM is written:

Important:To prevent indeterminate system behavior, reserved areas of memory must not be accessed bysoftware or hardware. Any area of the memory map that is not explicitly defined as a registerspace or accessible memory is considered reserved

And in this status register has some reserved bit fields.


Any suggestions?

0 Kudos
5 Replies


Can you try the code snippet below and let us know the results


static const struct socfpga_reset_manager *reset_manager_base = (void *)SOCFPGA_RSTMGR_ADDRESS;

int cause;

cause = readl(&reset_manager_base->status) &0xFFFFFFFF;





0 Kudos


No, it is not working. I will try some assembly routine tomorrow using tst instructions. I still think it is due to incorrect access or this is done after some code relocation and read a wrong place...

By the way what is the difference between your code and mine? I see in all cases always 0.

0 Kudos


Please let us know whether you are using a custom board 

also in the socfpga.dtsi file which you are using whether a cell similar to this is present 

rst: rstmgr@ffd05000 {

#reset-cells = <1>;

compatible = "altr,rst-mgr";

reg = <0xffd05000 0x1000>;

altr,modrst-offset = <0x10>;


if yes what is the address mentioned in the cell , is it same like ffd05000 or some thing else.

Also having reserved bits in a register doesn't mean that you cannot read the register. It means that you cannot change those bits or use it for some custom functionality.



0 Kudos

Hi Anil,

Before answering your question, one small update. We have SPL enabled and I moved my code in the very beginning of board_init_f:

@@ -306,6 +310,7 @@ void board_init_f(ulong dummy) * First C code to run. Clear fake OCRAM ECC first as SBE * and DBE might triggered during power on */ + reset_cause = readl(&reset_manager_base->status); reg = readl(&sysmgr_regs->eccgrp_ocram); if (reg & SYSMGR_ECC_OCRAM_SERR) writel(SYSMGR_ECC_OCRAM_SERR | SYSMGR_ECC_OCRAM_EN, @@ -316,6 +321,7 @@ void board_init_f(ulong dummy)

And I am displaying it later when SPL partition index is printed.

Yes, the board is our design.

The cell in socfpga.dtsi is similar. Our missing "altr,modrst-offset = <0x10>;" and I added it just in case. The address is the same.

--- a/arch/arm/dts/socfpga.dtsi +++ b/arch/arm/dts/socfpga.dtsi @@ -754,6 +754,7 @@ #reset-cells = <1>; compatible = "altr,rst-mgr"; reg = <0xffd05000 0x1000>; + altr,modrst-offset = <0x10>; };

I also added in some desperate move in our dtsi the next:

--- a/arch/arm/dts/socfpga_cyclone5.dtsi +++ b/arch/arm/dts/socfpga_cyclone5.dtsi @@ -28,6 +28,10 @@ smplsel = <0>; }; + rstmgr@ffd05000 { + status = <0xffd05000>; + }; +

But without success.




P.S. Do you know how to make warm reset from u-boot. I found one thread here before one year, and the person was complaining the same as me with not custom board. But at least he had warm reset bit read.


0 Kudos

Hi Georgi,

It turns out as follows

The BootROM reads the reset manager stat register, then clears it. This is why when you read it is always zero.

However, the BootROM keeps a copy into an internal data structure, and passes a pointer to that data structure to the Preloader (typically U-Boot SPL) in register r0.

Then the Preloader can read the value from r0 + 0x38.

See the following excerpts from


Slave Interface and Status Register

The reset manager slave interface is used to control and monitor the reset states.

The status register (stat) in the reset manager contains the status of the reset requester. The register

contains a bit for each monitored reset request. The stat register captures all reset requests that have

occurred. Software is responsible for clearing the bits.

During the boot process, the Boot ROM copies the stat register value into memory before clearing it.

After booting, you can read the value of the reset status register at memory address (r0 + 0x0038). For

more information, refer to the "Shared Memory" section of the Booting and Configuration appendix.


Shared Memory

The shared memory contains information that the boot ROM code passes to the preloader. The boot ROM

code passes the location of shared memory to the preloader in register r0, as described in the HPS State on

Entry to Preloader section.

The shared memory holds the last value of the stat register in the Reset Manager Module and a version

number that is passed by the boot ROM. The value of the stat register in shared memory is only valid if

the version number passed by the boot ROM is 0x00000000. The table below shows where the stat

register value and version number reside in the shared memory as an offset from the address stored in

register r0.

So you would need to save it from initialization of SPL from offset 0x38 added to register r0 as it is passed by BootROM





0 Kudos