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authorValentine Barshak <vbarshak@ru.mvista.com>2007-10-26 04:16:40 +1000
committerJosh Boyer <jwboyer@linux.vnet.ibm.com>2007-11-01 07:13:43 -0500
commitd1dfc35d3a62122b85ca975b80dcbf4a0da0bebc (patch)
tree61a5b0969dc452f77d3ad87ca851f1f4237a2219 /arch/ppc
parent1d6b698764084510fe6168bb5b650165dced03ae (diff)
[POWERPC] 4xx: Workaround for the 440EP(x)/GR(x) processors identical PVR issue.
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 <vbarshak@ru.mvista.com> Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
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