title: Trying to Compile FreeRtos for Riscv .Error: Instruction csrr requires absolute expression
body: <p>i am trying to compile the FreeRTOS riscv_spike port, with riscv32-unknown-linux-gnu-gcc toolchain but got his error</p>
  
  <p>Error:
  ../../Source/portable/GCC/RISCV/port.c:121: Error: Instruction csrr requires absolute expression</p>
  
  <p>The following code is from port.c of freeRtos Source</p>
  
  <pre><code>    __asm volatile("csrr t0,mtime");
      __asm volatile("add t0,t0,%0" :: "r"(configTICK_CLOCK_HZ/configTICK_RATE_HZ));
      __asm volatile("csrw mtimecmp,t0");
  </code></pre>
  
  <p>can anyone describe me what changes i need to make?
  i guess the mtime, mtimecmp is invalid
  can i add this required definition in "encoding" file by reading the spec?</p>
  
  <p>thanks,</p>