Benjamin Herrenschmidt wrote: > On Thu, 2007-10-25 at 22:16 +0400, Valentine Barshak wrote: >> PowerPC 440EP(x) 440GR(x) processors have the same PVR values, since >> they have identical cores. However, FPU is not supported on GR(x) and >> enabling APU instruction broadcast in the CCR0 register (to enable FPU) >> may cause unpredictable results. There's no safe way to detect FPU >> support at runtime. This patch provides a workarund for the issue. >> We use a POWER6 "logical PVR approach". First, we identify all EP(x) >> and GR(x) processors as GR(x) ones (which is safe). Then we check >> the device tree cpu path. If we have a EP(x) processor entry, >> we call identify_cpu again with PVR | 0x8. This bit is always 0 >> in the real PVR. This way we enable FPU only for 440EP(x). >> >> Signed-off-by: Valentine Barshak <[EMAIL PROTECTED]> > > Why not just or-in the FPU feature bit ? > > Ben. > >
It's not enough. We need to enable APU instruction broadcast for EP(x) (call __init_fpu_44x in arch/powerpc/kernel/cpu_setup_44x.S). Or do you suggest to or-in FPU feature bit and enable APUIB later, not in the cpu_setup callback? Thanks, Valentine. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
