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MIPS: Add MAC2008 Support

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MAC2008 means the processor implemented IEEE754 style Fused MADD
instruction. It was introduced in Release3 but removed in Release5.

The toolchain support of MAC2008 have never landed except for Loongson
processors.

This patch aimed to disabled the MAC2008 if it's optional. For
MAC2008 only processors, we corrected math-emu behavior to align
with actual hardware behavior.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
[paulburton@kernel.org: Fixup MIPSr2-r5 check in cpu_set_fpu_2008.]
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: chenhc@lemote.com
Cc: paul.burton@mips.com
Cc: linux-kernel@vger.kernel.org
This commit is contained in:
Jiaxun Yang
2020-01-13 18:16:11 +08:00
committed by Paul Burton
parent 0a3d5b5777
commit ece276de2a
9 changed files with 141 additions and 44 deletions
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16
arch/mips/kernel/cpu-probe.c
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@@ -102,7 +102,12 @@ static void cpu_set_fpu_2008(struct cpuinfo_mips *c)
if (fir & MIPS_FPIR_HAS2008) {
fcsr = read_32bit_cp1_register(CP1_STATUS);
fcsr0 = fcsr & ~(FPU_CSR_ABS2008 | FPU_CSR_NAN2008);
/*
* MAC2008 toolchain never landed in real world, so we're only
* testing wether it can be disabled and don't try to enabled
* it.
*/
fcsr0 = fcsr & ~(FPU_CSR_ABS2008 | FPU_CSR_NAN2008 | FPU_CSR_MAC2008);
write_32bit_cp1_register(CP1_STATUS, fcsr0);
fcsr0 = read_32bit_cp1_register(CP1_STATUS);
@@ -112,6 +117,15 @@ static void cpu_set_fpu_2008(struct cpuinfo_mips *c)
write_32bit_cp1_register(CP1_STATUS, fcsr);
if (c->isa_level & (MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2)) {
/*
* The bit for MAC2008 might be reused by R6 in future,
* so we only test for R2-R5.
*/
if (fcsr0 & FPU_CSR_MAC2008)
c->options |= MIPS_CPU_MAC_2008_ONLY;
}
if (!(fcsr0 & FPU_CSR_NAN2008))
c->options |= MIPS_CPU_NAN_LEGACY;
if (fcsr1 & FPU_CSR_NAN2008)