From 9772e6775dde1f2b62f1ceb3525034d5e6782142 Mon Sep 17 00:00:00 2001
From: Dolu1990 <charles.papon.90@gmail.com>
Date: Wed, 27 Apr 2022 16:12:56 +0200
Subject: [PATCH] readme now document FPU / openocd limitations

---
 README.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/README.md b/README.md
index 1a8864b..70e63ae 100644
--- a/README.md
+++ b/README.md
@@ -750,6 +750,12 @@ Fpu 64/32 bits ->
   Artix 7 FMax    -> 165 Mhz 3728 LUT 3175 FF 
 ```
 
+Note that if you want to debug FPU code via the openocd_riscv.vexriscv target, you need to use the GDB from : 
+
+https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-20171231-x86_64-linux-centos6.tar.gz
+
+More recent versions of gdb will not detect the FPU. Also, the openocd_riscv.vexriscv can't read CSR/FPU registers, so to have visibility on the floating points values, you need to compile your code in -O0, which will force values to be stored in memory (and so, be visible)
+
 ### Plugins
 
 This chapter describes the currently implemented plugins.