Slow QSPI on TE0720: "Warning: SPI speed fallback to 100 kHz"

[AaronB]

Any tips on getting the QSPI boot to use the correct clock frequency when booting petalinux from QSPI?

I'm using a TE0720, the boot code shows "SoM: TE0720-00-0C  F SC REV:00"

Its installed on a custom board, and I'm trying to boot petalinux from QSPI.

eMMC boot is fast, but I can't do that because the system won't boot if there is no Micro SD card in the slot, due to the "voltage select" issue.  Having a placeholder micro SD card in the slot at all times is not an option for my use case.  I have had success with removing the external SD card from my hardware configuration, but I'm trying to avoid that if possible.

So now I'm trying QSPI booting, but it seems really slow. 

During boot, there is a warning about clock speed limited to 100kHz, followed by a long pause while the flash is read.  It takes 4 seconds to load a 12MB image.ub file, which is slower than my requirements will allow.

At the uboot command prompt, I can manually force a 50 MHz clock speed, and it loads in 2 seconds, which is better.

However, I'd like to know if there is something I can do to ensure faster QSPI clock speeds.

The Vivado config for the QSPI speeds is attached, and the device tree snippet that was automatically generated is shown below.  Note that it shows a max clock speed of 50Mhz (0x2faf080).

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                spi@e000d000 {
                        clock-names = "ref_clk", "pclk";
                        clocks = <0x1 0xa 0x1 0x2b>;
                        compatible = "xlnx,zynq-qspi-1.0";
                        status = "okay";
                        interrupt-parent = <0x4>;
                        interrupts = <0x0 0x13 0x4>;
                        reg = <0xe000d000 0x1000>;
                        #address-cells = <0x1>;
                        #size-cells = <0x0>;
                        is-dual = <0x0>;
                        num-cs = <0x1>;
                        spi-rx-bus-width = <0x4>;
                        spi-tx-bus-width = <0x4>;

                        flash@0 {
                                compatible = "jedec,spi-nor";
                                reg = <0x0>;
                                #address-cells = <0x1>;
                                #size-cells = <0x1>;
                                spi-max-frequency = <0x2faf080>;

                                partition@0x00000000 {
                                        label = "boot";
                                        reg = <0x0 0x500000>;
                                };

                                partition@0x00500000 {
                                        label = "bootenv";
                                        reg = <0x500000 0x20000>;
                                };

                                partition@0x00520000 {
                                        label = "kernel";
                                        reg = <0x520000 0xc10000>;
                                };

                                partition@0x01130000 {
                                        label = "data";
                                        reg = <0x1130000 0xed0000>;
                                };
                        };
                };


If I manually stop at the uboot prompt and measure things, I can MANUALLY configure the subsystem with a 50 Mhz clock.  How can I get this by default?

Here are some example uboot logs.
First, the default one I get by allowing the boot to continue on its own.  the read takes 4 seconds:

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[2023-11-21 11:32:17.373] Hit any key to stop autoboot:  0
[2023-11-21 11:32:17.376] Warning: SPI speed fallback to 100 kHz
[2023-11-21 11:32:17.380] SF: Detected n25q256 with page size 256 Bytes, erase size 4 KiB, total 32 MiB
[2023-11-21 11:32:17.387] device 0 offset 0x520000, size 0xc10000
[2023-11-21 11:32:21.448] SF: 12648448 bytes @ 0x520000 Read: OK

Next, one where I manually specify the speed option to 50Mhz, and it takes 2 seconds:

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[2023-11-21 11:37:46.725] Zynq> sf probe 0 50000000
[2023-11-21 11:37:54.960] SF: Detected n25q256 with page size 256 Bytes, erase size 4 KiB, total 32 MiB
[2023-11-21 11:37:54.968] Zynq> boot
[2023-11-21 11:38:01.401] SF: Detected n25q256 with page size 256 Bytes, erase size 4 KiB, total 32 MiB
[2023-11-21 11:38:01.407] device 0 offset 0x520000, size 0xc10000
[2023-11-21 11:38:03.446] SF: 12648448 bytes @ 0x520000 Read: OK


Finally, one where I manually set the speed to 100Khz as a comparison, and the read takes 4 seconds as we might expect:

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[2023-11-21 11:39:10.933] Zynq> sf probe 100000
[2023-11-21 11:39:21.905] SF: Detected n25q256 with page size 256 Bytes, erase size 4 KiB, total 32 MiB
[2023-11-21 11:39:21.912] Zynq> boot
[2023-11-21 11:39:25.408] SF: Detected n25q256 with page size 256 Bytes, erase size 4 KiB, total 32 MiB
[2023-11-21 11:39:25.415] device 0 offset 0x520000, size 0xc10000
[2023-11-21 11:39:29.477] SF: 12648448 bytes @ 0x520000 Read: OK


For the moment I will try manually overriding the u-boot variable that loads the kernel into memory and does an "sf probe 0".  If I change this to "sf probe 0 50000000", this may accomplish my goal, but I'm confused as to what might be going wrong in my configuration that requires this.

[M Kirberg]

Hi,

that is strange, what versions of tools are you on?

br

[AaronB]

Vivado 2018.1 and Petalinux 2019.1

[M Kirberg]

Ok...

One thing: please never mix Vivado and Petalinux versions. Though it might work this leads to problems.


Apart from that: We have no experience with the 20XX.1 versions, we only have designs for 20XX.2.
Can you try our reference design for the TE0720?