MIPS: cpu-probe: Set the write-combine CCA value on per core basis

Different cores use different CCA values to achieve write-combine
memory writes. For cores that do not support write-combine we
set the default value to CCA:2 (uncached, non-coherent) which is the
default value as set by the kernel.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7402/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

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

@@ -79,6 +79,11 @@ struct cpuinfo_mips {
 #define NUM_WATCH_REGS 4
 	u16			watch_reg_masks[NUM_WATCH_REGS];
 	unsigned int		kscratch_mask; /* Usable KScratch mask. */
+	/*
+	 * Cache Coherency attribute for write-combine memory writes.
+	 * (shifted by _CACHE_SHIFT)
+	 */
+	unsigned int		writecombine;
 } __attribute__((aligned(SMP_CACHE_BYTES)));
 
 extern struct cpuinfo_mips cpu_data[];

arch/mips/kernel/cpu-probe.c

@@ -27,6 +27,7 @@
 #include <asm/msa.h>
 #include <asm/watch.h>
 #include <asm/elf.h>
+#include <asm/pgtable-bits.h>
 #include <asm/spram.h>
 #include <asm/uaccess.h>
 
@@ -764,6 +765,7 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
 			break;
 		case PRID_REV_LOONGSON3A:
 			c->cputype = CPU_LOONGSON3;
+			c->writecombine = _CACHE_UNCACHED_ACCELERATED;
 			__cpu_name[cpu] = "ICT Loongson-3";
 			set_elf_platform(cpu, "loongson3a");
 			break;
@@ -798,67 +800,83 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
 
 static inline void cpu_probe_mips(struct cpuinfo_mips *c, unsigned int cpu)
 {
+	c->writecombine = _CACHE_UNCACHED_ACCELERATED;
 	switch (c->processor_id & PRID_IMP_MASK) {
 	case PRID_IMP_4KC:
 		c->cputype = CPU_4KC;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 4Kc";
 		break;
 	case PRID_IMP_4KEC:
 	case PRID_IMP_4KECR2:
 		c->cputype = CPU_4KEC;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 4KEc";
 		break;
 	case PRID_IMP_4KSC:
 	case PRID_IMP_4KSD:
 		c->cputype = CPU_4KSC;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 4KSc";
 		break;
 	case PRID_IMP_5KC:
 		c->cputype = CPU_5KC;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 5Kc";
 		break;
 	case PRID_IMP_5KE:
 		c->cputype = CPU_5KE;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 5KE";
 		break;
 	case PRID_IMP_20KC:
 		c->cputype = CPU_20KC;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 20Kc";
 		break;
 	case PRID_IMP_24K:
 		c->cputype = CPU_24K;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 24Kc";
 		break;
 	case PRID_IMP_24KE:
 		c->cputype = CPU_24K;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 24KEc";
 		break;
 	case PRID_IMP_25KF:
 		c->cputype = CPU_25KF;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 25Kc";
 		break;
 	case PRID_IMP_34K:
 		c->cputype = CPU_34K;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 34Kc";
 		break;
 	case PRID_IMP_74K:
 		c->cputype = CPU_74K;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 74Kc";
 		break;
 	case PRID_IMP_M14KC:
 		c->cputype = CPU_M14KC;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS M14Kc";
 		break;
 	case PRID_IMP_M14KEC:
 		c->cputype = CPU_M14KEC;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS M14KEc";
 		break;
 	case PRID_IMP_1004K:
 		c->cputype = CPU_1004K;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 1004Kc";
 		break;
 	case PRID_IMP_1074K:
 		c->cputype = CPU_1074K;
+		c->writecombine = _CACHE_UNCACHED;
 		__cpu_name[cpu] = "MIPS 1074Kc";
 		break;
 	case PRID_IMP_INTERAPTIV_UP:
@@ -932,6 +950,7 @@ static inline void cpu_probe_sibyte(struct cpuinfo_mips *c, unsigned int cpu)
 {
 	decode_configs(c);
 
+	c->writecombine = _CACHE_UNCACHED_ACCELERATED;
 	switch (c->processor_id & PRID_IMP_MASK) {
 	case PRID_IMP_SB1:
 		c->cputype = CPU_SB1;
@@ -1063,6 +1082,7 @@ static inline void cpu_probe_ingenic(struct cpuinfo_mips *c, unsigned int cpu)
 	switch (c->processor_id & PRID_IMP_MASK) {
 	case PRID_IMP_JZRISC:
 		c->cputype = CPU_JZRISC;
+		c->writecombine = _CACHE_UNCACHED_ACCELERATED;
 		__cpu_name[cpu] = "Ingenic JZRISC";
 		break;
 	default:
@@ -1169,6 +1189,7 @@ void cpu_probe(void)
 	c->processor_id = PRID_IMP_UNKNOWN;
 	c->fpu_id	= FPIR_IMP_NONE;
 	c->cputype	= CPU_UNKNOWN;
+	c->writecombine = _CACHE_UNCACHED;
 
 	c->processor_id = read_c0_prid();
 	switch (c->processor_id & PRID_COMP_MASK) {