MIPS: features: Add initial support for Segmentation Control registers

MIPS32R3 introduced a new set of Segmentation Control registers which
increase the flexibility of the segmented-based memory scheme.

Signed-off-by: Steven J. Hill <[e-mail]>
Signed-off-by: Markos Chandras <[e-mail]>
Signed-off-by: John Crispin <[e-mail]>
Patchwork: http://patchwork.linux-mips.org/patch/6131/

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

···
 #ifndef cpu_has_tlbinv
 #define cpu_has_tlbinv		(cpu_data[0].options & MIPS_CPU_TLBINV)
 #endif
+#ifndef cpu_has_segments
+#define cpu_has_segments	(cpu_data[0].options & MIPS_CPU_SEGMENTS)
+#endif
+
 
 /*
  * For the moment we don't consider R6000 and R8000 so we can assume that

arch/mips/include/asm/cpu.h

···
 #define MIPS_CPU_RIXI		0x00800000 /* CPU has TLB Read/eXec Inhibit */
 #define MIPS_CPU_MICROMIPS	0x01000000 /* CPU has microMIPS capability */
 #define MIPS_CPU_TLBINV		0x02000000 /* CPU supports TLBINV/F */
+#define MIPS_CPU_SEGMENTS	0x04000000 /* CPU supports Segmentation Control registers */
 
 /*
  * CPU ASE encodings

arch/mips/include/asm/mipsregs.h

···
 #define MIPS_FPIR_L		(_ULCAST_(1) << 21)
 #define MIPS_FPIR_F64		(_ULCAST_(1) << 22)
 
+/*
+ * Bits in the MIPS32 Memory Segmentation registers.
+ */
+#define MIPS_SEGCFG_PA_SHIFT	9
+#define MIPS_SEGCFG_PA		(_ULCAST_(127) << MIPS_SEGCFG_PA_SHIFT)
+#define MIPS_SEGCFG_AM_SHIFT	4
+#define MIPS_SEGCFG_AM		(_ULCAST_(7) << MIPS_SEGCFG_AM_SHIFT)
+#define MIPS_SEGCFG_EU_SHIFT	3
+#define MIPS_SEGCFG_EU		(_ULCAST_(1) << MIPS_SEGCFG_EU_SHIFT)
+#define MIPS_SEGCFG_C_SHIFT	0
+#define MIPS_SEGCFG_C		(_ULCAST_(7) << MIPS_SEGCFG_C_SHIFT)
+
+#define MIPS_SEGCFG_UUSK	_ULCAST_(7)
+#define MIPS_SEGCFG_USK		_ULCAST_(5)
+#define MIPS_SEGCFG_MUSUK	_ULCAST_(4)
+#define MIPS_SEGCFG_MUSK	_ULCAST_(3)
+#define MIPS_SEGCFG_MSK		_ULCAST_(2)
+#define MIPS_SEGCFG_MK		_ULCAST_(1)
+#define MIPS_SEGCFG_UK		_ULCAST_(0)
+
 #ifndef __ASSEMBLY__
 
 /*
···
 #define read_c0_ebase()		__read_32bit_c0_register($15, 1)
 #define write_c0_ebase(val)	__write_32bit_c0_register($15, 1, val)
 
+/* MIPSR3 */
+#define read_c0_segctl0()	__read_32bit_c0_register($5, 2)
+#define write_c0_segctl0(val)	__write_32bit_c0_register($5, 2, val)
+
+#define read_c0_segctl1()	__read_32bit_c0_register($5, 3)
+#define write_c0_segctl1(val)	__write_32bit_c0_register($5, 3, val)
+
+#define read_c0_segctl2()	__read_32bit_c0_register($5, 4)
+#define write_c0_segctl2(val)	__write_32bit_c0_register($5, 4, val)
 
 /* Cavium OCTEON (cnMIPS) */
 #define read_c0_cvmcount()	__read_ulong_c0_register($9, 6)

arch/mips/kernel/cpu-probe.c

···
 		c->options |= MIPS_CPU_MICROMIPS;
 	if (config3 & MIPS_CONF3_VZ)
 		c->ases |= MIPS_ASE_VZ;
+	if (config3 & MIPS_CONF3_SC)
+		c->options |= MIPS_CPU_SEGMENTS;
 
 	return config3 & MIPS_CONF_M;
 }