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Visitor gdeest
Visitor
3,458 Views
Registered: ‎01-22-2015

Device tree and default frequency for ZC706

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Hi,

 

I am trying to determine at which default frequency the ARM cores are driven when booting a SD-Card generated by SDSoC.

 

I have decompiled the device tree, and seem to find two possibly relevant sections. The first one is the CPU configuration:

 

cpu@0 {
            compatible = "arm,cortex-a9";
            device_type = "cpu";
            reg = <0x0>;
            clocks = <0x1 0x3>;
            clock-latency = <0x3e8>;
            cpu0-supply = <0x2>;
            operating-points = <0xa2c2b 0xf4240 0x51616 0xf4240>;
};

0x3e8 translates to 1000 in decimal ; I guess the number is in nanoseconds, so that would be 1ms, which I suspect is actually the latency of the real-time clock or something similar... Or maybe the number is in picoseconds, but that would mean the XC7Z045 is actually overclocked to 1GHz, which does not sound like a reasonable default.

 

The other section is the following:

 

clkc@100 {
    #clock-cells = <0x1>;
    compatible = "xlnx,ps7-clkc";
    fclk-enable = <0xf>;
    reg = <0x100 0x100>;
    ps-clk-frequency = <0x1fca055>;
    linux,phandle = <0x1>;
    phandle = <0x1>;
};

 

The number converts to 33333333 in decimal. My intuition tells me that this the correct number, meaning that the cores are running at 333.33333 MHz.

 

Does someone have any idea on this ?

 

Thanks in advance,

 

Gaël

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Xilinx Employee
Xilinx Employee
6,249 Views
Registered: ‎06-29-2015

Re: Device tree and default frequency for ZC706

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Hi gdeest,

 

The clocks in Zynq are configured in Vivado and set on the processor by programming the FSBL. There is no clocking info in the devicetree. You'll have to open the Vivado project that created the HDF used by petalinux to generate the Linux image to determine the clock frequency.

 

The other place you could look is in the *_hw.pfm file for the SDSoC platform that you're using (example, zybo file is located here: C:\Xilinx\SDSoC\2016.2\platforms\zybo) for something like:

 

<xd:clock xd:name="CPU" xd:instanceRef="ps7" xd:componentRef="processing_system7" xd:frequency="650.000000"

 

However, if you're using a zybo board the processor frequency is 650MHz, zc702 is 666MHz, and zc706 is 800MHz. 

 

Sam

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2 Replies
Xilinx Employee
Xilinx Employee
6,250 Views
Registered: ‎06-29-2015

Re: Device tree and default frequency for ZC706

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Hi gdeest,

 

The clocks in Zynq are configured in Vivado and set on the processor by programming the FSBL. There is no clocking info in the devicetree. You'll have to open the Vivado project that created the HDF used by petalinux to generate the Linux image to determine the clock frequency.

 

The other place you could look is in the *_hw.pfm file for the SDSoC platform that you're using (example, zybo file is located here: C:\Xilinx\SDSoC\2016.2\platforms\zybo) for something like:

 

<xd:clock xd:name="CPU" xd:instanceRef="ps7" xd:componentRef="processing_system7" xd:frequency="650.000000"

 

However, if you're using a zybo board the processor frequency is 650MHz, zc702 is 666MHz, and zc706 is 800MHz. 

 

Sam

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Visitor gdeest
Visitor
3,367 Views
Registered: ‎01-22-2015

Re: Device tree and default frequency for ZC706

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Hi sskalick,

 

Thank you very much. I can confirm that the PS7 frequency is set to 800MHz in zc706_hw.pfm - which is what I was looking for.

 

Gaël

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