MIPS: Remove unused R6000 support

The kernel contains a small amount of incomplete code aimed at
supporting old R6000 CPUs. This is:

  - Unused, as no machine selects CONFIG_SYS_HAS_CPU_R6000.

  - Broken, since there are glaring errors such as r6000_fpu.S moving
    the FCSR register to t1, then ignoring it & instead saving t0 into
    struct sigcontext...

  - A maintenance headache, since it's code that nobody can test which
    nevertheless imposes constraints on code which it shares with other
    machines.

Remove this incomplete & broken R6000 CPU support in order to clean up
and in preparation for changes which will no longer need to consider
dragging the pretense of R6000 support along with them.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16236/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -1627,14 +1627,6 @@ config CPU_R5500
 	  NEC VR5500 and VR5500A series processors implement 64-bit MIPS IV
 	  instruction set.
 
-config CPU_R6000
-	bool "R6000"
-	depends on SYS_HAS_CPU_R6000
-	select CPU_SUPPORTS_32BIT_KERNEL
-	help
-	  MIPS Technologies R6000 and R6000A series processors.  Note these
-	  processors are extremely rare and the support for them is incomplete.
-
 config CPU_NEVADA
 	bool "RM52xx"
 	depends on SYS_HAS_CPU_NEVADA
@@ -1950,9 +1942,6 @@ config SYS_HAS_CPU_R5432
 config SYS_HAS_CPU_R5500
 	bool
 
-config SYS_HAS_CPU_R6000
-	bool
-
 config SYS_HAS_CPU_NEVADA
 	bool
 
@@ -2180,7 +2169,7 @@ config PAGE_SIZE_32KB
 
 config PAGE_SIZE_64KB
 	bool "64kB"
-	depends on !CPU_R3000 && !CPU_TX39XX && !CPU_R6000
+	depends on !CPU_R3000 && !CPU_TX39XX
 	help
 	  Using 64kB page size will result in higher performance kernel at
 	  the price of higher memory consumption.  This option is available on
@@ -2248,11 +2237,11 @@ config CPU_HAS_PREFETCH
 
 config CPU_GENERIC_DUMP_TLB
 	bool
-	default y if !(CPU_R3000 || CPU_R6000 || CPU_R8000 || CPU_TX39XX)
+	default y if !(CPU_R3000 || CPU_R8000 || CPU_TX39XX)
 
 config CPU_R4K_FPU
 	bool
-	default y if !(CPU_R3000 || CPU_R6000 || CPU_TX39XX || CPU_CAVIUM_OCTEON)
+	default y if !(CPU_R3000 || CPU_TX39XX || CPU_CAVIUM_OCTEON)
 
 config CPU_R4K_CACHE_TLB
 	bool

arch/mips/Makefile

@@ -151,7 +151,6 @@ cflags-y += -fno-stack-check
 #
 cflags-$(CONFIG_CPU_R3000)	+= -march=r3000
 cflags-$(CONFIG_CPU_TX39XX)	+= -march=r3900
-cflags-$(CONFIG_CPU_R6000)	+= -march=r6000 -Wa,--trap
 cflags-$(CONFIG_CPU_R4300)	+= -march=r4300 -Wa,--trap
 cflags-$(CONFIG_CPU_VR41XX)	+= -march=r4100 -Wa,--trap
 cflags-$(CONFIG_CPU_R4X00)	+= -march=r4600 -Wa,--trap

arch/mips/include/asm/cpu-type.h

@@ -151,11 +151,6 @@ static inline int __pure __get_cpu_type(const int cpu_type)
 	case CPU_R5500:
 #endif
 
-#ifdef CONFIG_SYS_HAS_CPU_R6000
-	case CPU_R6000:
-	case CPU_R6000A:
-#endif
-
 #ifdef CONFIG_SYS_HAS_CPU_NEVADA
 	case CPU_NEVADA:
 #endif

arch/mips/include/asm/cpu.h

@@ -285,11 +285,6 @@ enum cpu_type_enum {
 	CPU_R2000, CPU_R3000, CPU_R3000A, CPU_R3041, CPU_R3051, CPU_R3052,
 	CPU_R3081, CPU_R3081E,
 
-	/*
-	 * R6000 class processors
-	 */
-	CPU_R6000, CPU_R6000A,
-
 	/*
 	 * R4000 class processors
 	 */

arch/mips/include/asm/module.h

@@ -114,8 +114,6 @@ search_module_dbetables(unsigned long addr)
 #define MODULE_PROC_FAMILY "R5432 "
 #elif defined CONFIG_CPU_R5500
 #define MODULE_PROC_FAMILY "R5500 "
-#elif defined CONFIG_CPU_R6000
-#define MODULE_PROC_FAMILY "R6000 "
 #elif defined CONFIG_CPU_NEVADA
 #define MODULE_PROC_FAMILY "NEVADA "
 #elif defined CONFIG_CPU_R8000

arch/mips/kernel/Makefile

@@ -37,7 +37,6 @@ obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o ftrace.o
 
 obj-$(CONFIG_CPU_R4K_FPU)	+= r4k_fpu.o r4k_switch.o
 obj-$(CONFIG_CPU_R3000)		+= r2300_fpu.o r2300_switch.o
-obj-$(CONFIG_CPU_R6000)		+= r6000_fpu.o r4k_switch.o
 obj-$(CONFIG_CPU_TX39XX)	+= r2300_fpu.o r2300_switch.o
 obj-$(CONFIG_CPU_CAVIUM_OCTEON)	+= r4k_fpu.o octeon_switch.o
 

arch/mips/kernel/cpu-probe.c

@@ -1394,24 +1394,6 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
 			     MIPS_CPU_DIVEC | MIPS_CPU_LLSC;
 		c->tlbsize = 48;
 		break;
-	case PRID_IMP_R6000:
-		c->cputype = CPU_R6000;
-		__cpu_name[cpu] = "R6000";
-		set_isa(c, MIPS_CPU_ISA_II);
-		c->fpu_msk31 |= FPU_CSR_CONDX | FPU_CSR_FS;
-		c->options = MIPS_CPU_TLB | MIPS_CPU_FPU |
-			     MIPS_CPU_LLSC;
-		c->tlbsize = 32;
-		break;
-	case PRID_IMP_R6000A:
-		c->cputype = CPU_R6000A;
-		__cpu_name[cpu] = "R6000A";
-		set_isa(c, MIPS_CPU_ISA_II);
-		c->fpu_msk31 |= FPU_CSR_CONDX | FPU_CSR_FS;
-		c->options = MIPS_CPU_TLB | MIPS_CPU_FPU |
-			     MIPS_CPU_LLSC;
-		c->tlbsize = 32;
-		break;
 	case PRID_IMP_RM7000:
 		c->cputype = CPU_RM7000;
 		__cpu_name[cpu] = "RM7000";

arch/mips/kernel/r6000_fpu.S

@@ -1,99 +0,0 @@
-/*
- * r6000_fpu.S: Save/restore floating point context for signal handlers.
- *
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 1996 by Ralf Baechle
- *
- * Multi-arch abstraction and asm macros for easier reading:
- * Copyright (C) 1996 David S. Miller (davem@davemloft.net)
- */
-#include <asm/asm.h>
-#include <asm/fpregdef.h>
-#include <asm/mipsregs.h>
-#include <asm/asm-offsets.h>
-#include <asm/regdef.h>
-
-	.set	noreorder
-	.set	mips2
-	.set	push
-	SET_HARDFLOAT
-
-/**
- * _save_fp_context() - save FP context from the FPU
- * @a0 - pointer to fpregs field of sigcontext
- * @a1 - pointer to fpc_csr field of sigcontext
- *
- * Save FP context, including the 32 FP data registers and the FP
- * control & status register, from the FPU to signal context.
- */
-	LEAF(_save_fp_context)
-	mfc0	t0,CP0_STATUS
-	sll	t0,t0,2
-	bgez	t0,1f
-	 nop
-
-	cfc1	t1,fcr31
-	/* Store the 16 double precision registers */
-	sdc1	$f0,0(a0)
-	sdc1	$f2,16(a0)
-	sdc1	$f4,32(a0)
-	sdc1	$f6,48(a0)
-	sdc1	$f8,64(a0)
-	sdc1	$f10,80(a0)
-	sdc1	$f12,96(a0)
-	sdc1	$f14,112(a0)
-	sdc1	$f16,128(a0)
-	sdc1	$f18,144(a0)
-	sdc1	$f20,160(a0)
-	sdc1	$f22,176(a0)
-	sdc1	$f24,192(a0)
-	sdc1	$f26,208(a0)
-	sdc1	$f28,224(a0)
-	sdc1	$f30,240(a0)
-	jr	ra
-	 sw	t0,(a1)
-1:	jr	ra
-	 nop
-	END(_save_fp_context)
-
-/**
- * _restore_fp_context() - restore FP context to the FPU
- * @a0 - pointer to fpregs field of sigcontext
- * @a1 - pointer to fpc_csr field of sigcontext
- *
- * Restore FP context, including the 32 FP data registers and the FP
- * control & status register, from signal context to the FPU.
- */
-	LEAF(_restore_fp_context)
-	mfc0	t0,CP0_STATUS
-	sll	t0,t0,2
-
-	bgez	t0,1f
-	 lw	t0,(a1)
-	/* Restore the 16 double precision registers */
-	ldc1	$f0,0(a0)
-	ldc1	$f2,16(a0)
-	ldc1	$f4,32(a0)
-	ldc1	$f6,48(a0)
-	ldc1	$f8,64(a0)
-	ldc1	$f10,80(a0)
-	ldc1	$f12,96(a0)
-	ldc1	$f14,112(a0)
-	ldc1	$f16,128(a0)
-	ldc1	$f18,144(a0)
-	ldc1	$f20,160(a0)
-	ldc1	$f22,176(a0)
-	ldc1	$f24,192(a0)
-	ldc1	$f26,208(a0)
-	ldc1	$f28,224(a0)
-	ldc1	$f30,240(a0)
-	jr	ra
-	 ctc1	t0,fcr31
-1:	jr	ra
-	 nop
-	END(_restore_fp_context)
-
-	.set pop	/* SET_HARDFLOAT */

arch/mips/kernel/traps.c

@@ -2428,21 +2428,6 @@ void __init trap_init(void)
 	set_except_vector(EXCCODE_TR, handle_tr);
 	set_except_vector(EXCCODE_MSAFPE, handle_msa_fpe);
 
-	if (current_cpu_type() == CPU_R6000 ||
-	    current_cpu_type() == CPU_R6000A) {
-		/*
-		 * The R6000 is the only R-series CPU that features a machine
-		 * check exception (similar to the R4000 cache error) and
-		 * unaligned ldc1/sdc1 exception.  The handlers have not been
-		 * written yet.	 Well, anyway there is no R6000 machine on the
-		 * current list of targets for Linux/MIPS.
-		 * (Duh, crap, there is someone with a triple R6k machine)
-		 */
-		//set_except_vector(14, handle_mc);
-		//set_except_vector(15, handle_ndc);
-	}
-
-
 	if (board_nmi_handler_setup)
 		board_nmi_handler_setup();
 

arch/mips/mm/tlbex.c

@@ -2634,11 +2634,6 @@ void build_tlb_refill_handler(void)
 #endif
 		break;
 
-	case CPU_R6000:
-	case CPU_R6000A:
-		panic("No R6000 TLB refill handler yet");
-		break;
-
 	case CPU_R8000:
 		panic("No R8000 TLB refill handler yet");
 		break;