On Wed, Aug 14, 2019 at 09:00:14AM +0800, Alan Kao wrote: > But it doesn't really mean that the running system has an FPU given CONFIG_FPU > enabled. Normally the existence of an FPU is checked in riscv_fill_hwcap by > searching device tree, where the code looks like > > > bool has_fpu = false; // this one is global > ... > #ifdef CONFIG_FPU > if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)) > has_fpu = true; > #endif > > > Or does CONFIG_FPU have a more intuitive meaning when CONFIG_M_MODE is > enabled?
No, it doesn't.. > > > + csrr t0, CSR_MISA > > + andi t0, t0, (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D) > > + bnez t0, .Lreset_regs_done ... which is why we have these few lines of code that check the caps returns from the misa CSR, similar to the elf_caps check quoted above.
