From cc97ab235f3fe32401ca198cebe6f42642e95770 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Wed, 7 Nov 2018 23:13:59 +0000 Subject: MIPS: Simplify FP context initialization MIPS has up until now had 3 different ways for a task's floating point context to be initialized: - If the task's first use of FP involves it gaining ownership of an FPU then _init_fpu() is used to initialize the FPU's registers such that they all contain ~0, and the FPU registers will be stored to struct thread_info later (eg. when context switching). - If the task first uses FP on a CPU without an associated FPU then fpu_emulator_init_fpu() initializes the task's floating point register state in struct thread_info such that all floating point register contain the bit pattern 0x7ff800007ff80000, different to the _init_fpu() behaviour. - If a task's floating point context is first accessed via ptrace then init_fp_ctx() initializes the floating point register state in struct thread_info to ~0, giving equivalent state to _init_fpu(). The _init_fpu() path has 2 separate implementations - one for r2k/r3k style systems & one for r4k style systems. The _init_fpu() path also requires that we be careful to clear & restore the value of the Config5.FRE bit on modern systems in order to avoid inadvertently triggering floating point exceptions. None of this code is in a performance critical hot path - it runs only the first time a task uses floating point. As such it doesn't seem to warrant the complications of maintaining the _init_fpu() path. Remove _init_fpu() & fpu_emulator_init_fpu(), instead using init_fp_ctx() consistently to initialize floating point register state in struct thread_info. Upon a task's first use of floating point this will typically mean that we initialize state in memory & then load it into FPU registers using _restore_fp() just as we would on a context switch. For other paths such as __compute_return_epc_for_insn() or mipsr2_decoder() this results in a significant simplification of the work to be done. Signed-off-by: Paul Burton Patchwork: https://patchwork.linux-mips.org/patch/21002/ Cc: linux-mips@linux-mips.org --- arch/mips/kernel/r2300_fpu.S | 58 -------------------------------------------- 1 file changed, 58 deletions(-) (limited to 'arch/mips/kernel/r2300_fpu.S') diff --git a/arch/mips/kernel/r2300_fpu.S b/arch/mips/kernel/r2300_fpu.S index 3062ba66c563..12e58053544f 100644 --- a/arch/mips/kernel/r2300_fpu.S +++ b/arch/mips/kernel/r2300_fpu.S @@ -52,64 +52,6 @@ LEAF(_restore_fp) jr ra END(_restore_fp) -/* - * Load the FPU with signalling NANS. This bit pattern we're using has - * the property that no matter whether considered as single or as double - * precision represents signaling NANS. - * - * The value to initialize fcr31 to comes in $a0. - */ - - .set push - SET_HARDFLOAT - -LEAF(_init_fpu) - mfc0 t0, CP0_STATUS - li t1, ST0_CU1 - or t0, t1 - mtc0 t0, CP0_STATUS - - ctc1 a0, fcr31 - - li t0, -1 - - mtc1 t0, $f0 - mtc1 t0, $f1 - mtc1 t0, $f2 - mtc1 t0, $f3 - mtc1 t0, $f4 - mtc1 t0, $f5 - mtc1 t0, $f6 - mtc1 t0, $f7 - mtc1 t0, $f8 - mtc1 t0, $f9 - mtc1 t0, $f10 - mtc1 t0, $f11 - mtc1 t0, $f12 - mtc1 t0, $f13 - mtc1 t0, $f14 - mtc1 t0, $f15 - mtc1 t0, $f16 - mtc1 t0, $f17 - mtc1 t0, $f18 - mtc1 t0, $f19 - mtc1 t0, $f20 - mtc1 t0, $f21 - mtc1 t0, $f22 - mtc1 t0, $f23 - mtc1 t0, $f24 - mtc1 t0, $f25 - mtc1 t0, $f26 - mtc1 t0, $f27 - mtc1 t0, $f28 - mtc1 t0, $f29 - mtc1 t0, $f30 - mtc1 t0, $f31 - jr ra - END(_init_fpu) - - .set pop - .set noreorder /** -- cgit