From 36dc5b20e31db5cd470eb1934815320e7a0434c3 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Tue, 7 Aug 2018 10:15:04 -0700 Subject: MIPS: Use dins to simplify __write_64bit_c0_split() The code in __write_64bit_c0_split() is used by MIPS32 kernels running on MIPS64 CPUs to write a 64-bit value to a 64-bit coprocessor 0 register using a single 64-bit dmtc0 instruction. It does this by combining the 2x 32-bit registers used to hold the 64-bit value into a single register, which in the existing code involves three steps: 1) Zero extend register A which holds bits 31:0 of our data, since it may have previously held a sign-extended value. 2) Shift register B which holds bits 63:32 of our data in bits 31:0 left by 32 bits, such that the bits forming our data are in the position they'll be in the final 64-bit value & bits 31:0 of the register are zero. 3) Or the two registers together to form the 64-bit value in one 64-bit register. From MIPS r2 onwards we have a dins instruction which can effectively perform all 3 of those steps using a single instruction. Add a path for MIPS r2 & beyond which uses dins to take bits 31:0 from register B & insert them into bits 63:32 of register A, giving us our full 64-bit value in register A with one instruction. Since we know that MIPS r2 & above support the sel field for the dmtc0 instruction, we don't bother special casing sel==0. Omiting the sel field would assemble to exactly the same instruction as when we explicitly specify that it equals zero. Signed-off-by: Paul Burton --- arch/mips/include/asm/mipsregs.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'arch/mips/include/asm/mipsregs.h') diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h index dd46ab2a4ffd..a3ee982b4c1a 100644 --- a/arch/mips/include/asm/mipsregs.h +++ b/arch/mips/include/asm/mipsregs.h @@ -16,6 +16,7 @@ #include #include #include +#include #include /* @@ -1489,7 +1490,15 @@ do { \ unsigned long __flags; \ \ local_irq_save(__flags); \ - if (sel == 0) \ + if (MIPS_ISA_REV >= 2) \ + __asm__ __volatile__( \ + ".set\tpush\n\t" \ + ".set\t" MIPS_ISA_LEVEL "\n\t" \ + "dins\t%L0, %M0, 32, 32\n\t" \ + "dmtc0\t%L0, " #source ", " #sel "\n\t" \ + ".set\tpop" \ + : "+r" (__tmp)); \ + else if (sel == 0) \ __asm__ __volatile__( \ ".set\tmips64\n\t" \ "dsll\t%L0, %L0, 32\n\t" \ -- cgit v1.2.3