Error booting Linux using default LargeBoomConfig on VCU118

[Reese Kuper]

Hi everyone,

I am trying to use chipyard (v1.10.0) to boot Linux on the large BOOM core using the VCU118 FPGA. I have used chipyard last year (v1.5) and was able to generate a bitstream using the large BOOM core that was able to boot into Linux successfully. 

With the default configurations of chipyard v1.10.0, I see an error saying that I am using a non-homogeneous clock (BOOM core at 50MHz, FPGA clocks and harness binder set to 100MHz). If I set the BoomVCU118Config frequency to 100MHz, synthesis results in design timing not being met (< -0.7 in WNS). If I switch all frequencies to 50MHz, timing is met, but cannot successfully boot into Linux (stuck at "CMD0; sd_cmd: timeout; ERROR").

How can I boot into Linux using the LargeBoomConfig?

Thanks in advance,
Reese

[Elkim Roa]

It looks like the SPI freq. for the SDCard interface is too low. Line 33 of chipyard/fpga/src/main/scala/vcu118/Configs.scala is normalizing the frequency to MHz  

val freqMHz = (site(SystemBusKey).dtsFrequency.get / (1000 * 1000)).toLong

but the sd.c at chipyard/fpga/src/main/resources/vcu118/sdboot is using Hz:

REG32(spi, SPI_REG_SCKDIV) = (F_CLK / 300000UL);

Solution, divide in MHz instead (300000) --> 0.3 (0.3MHz). Use 0.4 instead since that is the expected freq by the MCU within the SDcard. Chnage line 179 too in sd.c accordingly! (20MHz works ok).