🐛 [sw] fixed bug in bootloader's (M)TIME handling #267
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recompiled due to bugs in bootloader sources
do not use time CSRs as they might no be available (no Zicntr ISA extension)
recompiled due to bugs in neorv32_cpu_delay_ms function
bug-fix in bootloader's (M)TIME handling
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This PR fixes a bug in the bootloader's handling of the system time timer (MTIME), which is used the generate the blinking status LED and the "autoboot timeout".
The bootloader used the
time[h]CSRs to access the current system time (these CSRs are driven by the MTIME unit). If theZicntrISA extensions is not enabled ( =time[h], cycle[h] andinstret[h]CSRs not available) the bootloader crashed.A second (minor) bug has also been fixed: when using the MTIME for generating precise timer interrupts, the interrupt handler has to update the MTIME.TIMECMP value. This has to be done by adding a fixed amount of cycles (= the time between interrupts) to the MTIME.TIMECMP value itself. To illustrate this issue, a demo program for the RISC-V machine timer MTIME has been added to
sw/example/demo_mtime.