mor edoc about litex/debian

source/NaxRiscv/hardware/index.rst

@@ -77,7 +77,7 @@ python3 -m litex_boards.targets.digilent_nexys_video --cpu-type=naxriscv --with
 
 Then all should be good. You can login with user "root" password "root". You can also connect via SSH to root.
 
-The bottleneck of the system is by far accessing the spi-sdcard. (500 KB/s read speed), so, things take time the first time you run them. Then it is much faster (linux cached stuff).
+The bottleneck of the system is by far accessing the spi-sdcard. (500 KB/s read speed), so, things take time the first time you run them. Then it is much faster (linux cached stuff). So, instead of --with-spi-sdcard, consider using --with-coherent-dma --with-sdcard with the driver patch described in https://github.com/SpinalHDL/NaxSoftware/tree/main/debian_litex, this will allow the SoC to reach 4MB/s on the sdcard.
 
 The Debian chroot (part2) was generated by following https://wiki.debian.org/RISC-V#Creating_a_riscv64_chroot and https://github.com/tongchen126/Boot-Debian-On-Litex-Rocket/blob/main/README.md#step3-build-debian-rootfs.
 Also, it was generated inside QEMU, using https://github.com/esmil/riscv-linux "make sid"