MIPS: Cleanup CP0 PRId and CP1 FPIR register access masks

Replace hardcoded CP0 PRId and CP1 FPIR register access masks throughout.
The change does not touch places that use shifted or partial masks.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5838/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

12 files changed, 77 insertions, 45 deletions

diff --git a/arch/mips/alchemy/common/usb.c b/arch/mips/alchemy/common/usb.c
index fcc695626117..2adc7edda49c 100644
--- a/arch/mips/alchemy/common/usb.c
+++ b/arch/mips/alchemy/common/usb.c
@@ -14,6 +14,7 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/syscore_ops.h>
+#include <asm/cpu.h>
 #include <asm/mach-au1x00/au1000.h>
 
 /* control register offsets */
@@ -358,7 +359,7 @@ static inline int au1200_coherency_bug(void)
 {
 #if defined(CONFIG_DMA_COHERENT)
         /* Au1200 AB USB does not support coherent memory */
-        if (!(read_c0_prid() & 0xff)) {
+        if (!(read_c0_prid() & PRID_REV_MASK)) {
                 printk(KERN_INFO "Au1200 USB: this is chip revision AB !!\n");
                 printk(KERN_INFO "Au1200 USB: update your board or re-configure"
                                  " the kernel\n");
diff --git a/arch/mips/bcm63xx/cpu.c b/arch/mips/bcm63xx/cpu.c
index 7e17374a9ae8..b713cd64b087 100644
--- a/arch/mips/bcm63xx/cpu.c
+++ b/arch/mips/bcm63xx/cpu.c
@@ -306,14 +306,14 @@ void __init bcm63xx_cpu_init(void)
 
         switch (c->cputype) {
         case CPU_BMIPS3300:
-                if ((read_c0_prid() & 0xff00) != PRID_IMP_BMIPS3300_ALT)
+                if ((read_c0_prid() & PRID_IMP_MASK) != PRID_IMP_BMIPS3300_ALT)
                         __cpu_name[cpu] = "Broadcom BCM6338";
                 /* fall-through */
         case CPU_BMIPS32:
                 chipid_reg = BCM_6345_PERF_BASE;
                 break;
         case CPU_BMIPS4350:
-                switch ((read_c0_prid() & 0xff)) {
+                switch ((read_c0_prid() & PRID_REV_MASK)) {
                 case 0x04:
                         chipid_reg = BCM_3368_PERF_BASE;
                         break;
diff --git a/arch/mips/include/asm/cpu.h b/arch/mips/include/asm/cpu.h
index 71b9f1998be7..d2035e16502a 100644
--- a/arch/mips/include/asm/cpu.h
+++ b/arch/mips/include/asm/cpu.h
@@ -3,15 +3,14 @@
  *        various MIPS cpu types.
  *
  * Copyright (C) 1996 David S. Miller (davem@davemloft.net)
- * Copyright (C) 2004  Maciej W. Rozycki
+ * Copyright (C) 2004, 2013  Maciej W. Rozycki
  */
 #ifndef _ASM_CPU_H
 #define _ASM_CPU_H
 
-/* Assigned Company values for bits 23:16 of the PRId Register
-   (CP0 register 15, select 0).  As of the MIPS32 and MIPS64 specs from
-   MTI, the PRId register is defined in this (backwards compatible)
-   way:
+/*
+   As of the MIPS32 and MIPS64 specs from MTI, the PRId register (CP0
+   register 15, select 0) is defined in this (backwards compatible) way:
 
   +----------------+----------------+----------------+----------------+
   | Company Options| Company ID     | Processor ID   | Revision       |
@@ -23,6 +22,14 @@
    spec.
 */
 
+#define PRID_OPT_MASK           0xff000000
+
+/*
+ * Assigned Company values for bits 23:16 of the PRId register.
+ */
+
+#define PRID_COMP_MASK          0xff0000
+
 #define PRID_COMP_LEGACY        0x000000
 #define PRID_COMP_MIPS          0x010000
 #define PRID_COMP_BROADCOM      0x020000
@@ -38,10 +45,17 @@
 #define PRID_COMP_INGENIC       0xd00000
 
 /*
- * Assigned values for the product ID register.  In order to detect a
- * certain CPU type exactly eventually additional registers may need to
- * be examined.  These are valid when 23:16 == PRID_COMP_LEGACY
+ * Assigned Processor ID (implementation) values for bits 15:8 of the PRId
+ * register.  In order to detect a certain CPU type exactly eventually
+ * additional registers may need to be examined.
  */
+
+#define PRID_IMP_MASK           0xff00
+
+/*
+ * These are valid when 23:16 == PRID_COMP_LEGACY
+ */
+
 #define PRID_IMP_R2000          0x0100
 #define PRID_IMP_AU1_REV1       0x0100
 #define PRID_IMP_AU1_REV2       0x0200
@@ -182,11 +196,15 @@
 #define PRID_IMP_NETLOGIC_XLP2XX        0x1200
 
 /*
- * Definitions for 7:0 on legacy processors
+ * Particular Revision values for bits 7:0 of the PRId register.
  */
 
 #define PRID_REV_MASK           0x00ff
 
+/*
+ * Definitions for 7:0 on legacy processors
+ */
+
 #define PRID_REV_TX4927         0x0022
 #define PRID_REV_TX4937         0x0030
 #define PRID_REV_R4400          0x0040
@@ -227,6 +245,8 @@
  *  31                             16 15             8 7              0
  */
 
+#define FPIR_IMP_MASK           0xff00
+
 #define FPIR_IMP_NONE           0x0000
 
 enum cpu_type_enum {
diff --git a/arch/mips/include/asm/mach-au1x00/au1000.h b/arch/mips/include/asm/mach-au1x00/au1000.h
index 3e11a468cdf8..54f9e84db8ac 100644
--- a/arch/mips/include/asm/mach-au1x00/au1000.h
+++ b/arch/mips/include/asm/mach-au1x00/au1000.h
@@ -43,6 +43,8 @@
 #include <linux/io.h>
 #include <linux/irq.h>
 
+#include <asm/cpu.h>
+
 /* cpu pipeline flush */
 void static inline au_sync(void)
 {
@@ -140,7 +142,7 @@ static inline int au1xxx_cpu_needs_config_od(void)
 
 static inline int alchemy_get_cputype(void)
 {
-        switch (read_c0_prid() & 0xffff0000) {
+        switch (read_c0_prid() & (PRID_OPT_MASK | PRID_COMP_MASK)) {
         case 0x00030000:
                 return ALCHEMY_CPU_AU1000;
                 break;
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 9ef2b049d3c0..9be68091bdf2 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -123,7 +123,7 @@ static inline unsigned long cpu_get_fpu_id(void)
  */
 static inline int __cpu_has_fpu(void)
 {
-        return ((cpu_get_fpu_id() & 0xff00) != FPIR_IMP_NONE);
+        return ((cpu_get_fpu_id() & FPIR_IMP_MASK) != FPIR_IMP_NONE);
 }
 
 static inline void cpu_probe_vmbits(struct cpuinfo_mips *c)
@@ -323,7 +323,7 @@ static void decode_configs(struct cpuinfo_mips *c)
 
 static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
 {
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_R2000:
                 c->cputype = CPU_R2000;
                 __cpu_name[cpu] = "R2000";
@@ -334,7 +334,7 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
                 c->tlbsize = 64;
                 break;
         case PRID_IMP_R3000:
-                if ((c->processor_id & 0xff) == PRID_REV_R3000A) {
+                if ((c->processor_id & PRID_REV_MASK) == PRID_REV_R3000A) {
                         if (cpu_has_confreg()) {
                                 c->cputype = CPU_R3081E;
                                 __cpu_name[cpu] = "R3081";
@@ -354,7 +354,8 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
                 break;
         case PRID_IMP_R4000:
                 if (read_c0_config() & CONF_SC) {
-                        if ((c->processor_id & 0xff) >= PRID_REV_R4400) {
+                        if ((c->processor_id & PRID_REV_MASK) >=
+                            PRID_REV_R4400) {
                                 c->cputype = CPU_R4400PC;
                                 __cpu_name[cpu] = "R4400PC";
                         } else {
@@ -362,7 +363,8 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
                                 __cpu_name[cpu] = "R4000PC";
                         }
                 } else {
-                        if ((c->processor_id & 0xff) >= PRID_REV_R4400) {
+                        if ((c->processor_id & PRID_REV_MASK) >=
+                            PRID_REV_R4400) {
                                 c->cputype = CPU_R4400SC;
                                 __cpu_name[cpu] = "R4400SC";
                         } else {
@@ -455,7 +457,7 @@ static inline void cpu_probe_legacy(struct cpuinfo_mips *c, unsigned int cpu)
                         __cpu_name[cpu] = "TX3927";
                         c->tlbsize = 64;
                 } else {
-                        switch (c->processor_id & 0xff) {
+                        switch (c->processor_id & PRID_REV_MASK) {
                         case PRID_REV_TX3912:
                                 c->cputype = CPU_TX3912;
                                 __cpu_name[cpu] = "TX3912";
@@ -641,7 +643,7 @@ 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)
 {
         decode_configs(c);
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_4KC:
                 c->cputype = CPU_4KC;
                 __cpu_name[cpu] = "MIPS 4Kc";
@@ -712,7 +714,7 @@ static inline void cpu_probe_mips(struct cpuinfo_mips *c, unsigned int cpu)
 static inline void cpu_probe_alchemy(struct cpuinfo_mips *c, unsigned int cpu)
 {
         decode_configs(c);
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_AU1_REV1:
         case PRID_IMP_AU1_REV2:
                 c->cputype = CPU_ALCHEMY;
@@ -731,7 +733,7 @@ static inline void cpu_probe_alchemy(struct cpuinfo_mips *c, unsigned int cpu)
                         break;
                 case 4:
                         __cpu_name[cpu] = "Au1200";
-                        if ((c->processor_id & 0xff) == 2)
+                        if ((c->processor_id & PRID_REV_MASK) == 2)
                                 __cpu_name[cpu] = "Au1250";
                         break;
                 case 5:
@@ -749,12 +751,12 @@ static inline void cpu_probe_sibyte(struct cpuinfo_mips *c, unsigned int cpu)
 {
         decode_configs(c);
 
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_SB1:
                 c->cputype = CPU_SB1;
                 __cpu_name[cpu] = "SiByte SB1";
                 /* FPU in pass1 is known to have issues. */
-                if ((c->processor_id & 0xff) < 0x02)
+                if ((c->processor_id & PRID_REV_MASK) < 0x02)
                         c->options &= ~(MIPS_CPU_FPU | MIPS_CPU_32FPR);
                 break;
         case PRID_IMP_SB1A:
@@ -767,7 +769,7 @@ static inline void cpu_probe_sibyte(struct cpuinfo_mips *c, unsigned int cpu)
 static inline void cpu_probe_sandcraft(struct cpuinfo_mips *c, unsigned int cpu)
 {
         decode_configs(c);
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_SR71000:
                 c->cputype = CPU_SR71000;
                 __cpu_name[cpu] = "Sandcraft SR71000";
@@ -780,7 +782,7 @@ static inline void cpu_probe_sandcraft(struct cpuinfo_mips *c, unsigned int cpu)
 static inline void cpu_probe_nxp(struct cpuinfo_mips *c, unsigned int cpu)
 {
         decode_configs(c);
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_PR4450:
                 c->cputype = CPU_PR4450;
                 __cpu_name[cpu] = "Philips PR4450";
@@ -792,7 +794,7 @@ static inline void cpu_probe_nxp(struct cpuinfo_mips *c, unsigned int cpu)
 static inline void cpu_probe_broadcom(struct cpuinfo_mips *c, unsigned int cpu)
 {
         decode_configs(c);
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_BMIPS32_REV4:
         case PRID_IMP_BMIPS32_REV8:
                 c->cputype = CPU_BMIPS32;
@@ -807,7 +809,7 @@ static inline void cpu_probe_broadcom(struct cpuinfo_mips *c, unsigned int cpu)
                 set_elf_platform(cpu, "bmips3300");
                 break;
         case PRID_IMP_BMIPS43XX: {
-                int rev = c->processor_id & 0xff;
+                int rev = c->processor_id & PRID_REV_MASK;
 
                 if (rev >= PRID_REV_BMIPS4380_LO &&
                                 rev <= PRID_REV_BMIPS4380_HI) {
@@ -833,7 +835,7 @@ static inline void cpu_probe_broadcom(struct cpuinfo_mips *c, unsigned int cpu)
 static inline void cpu_probe_cavium(struct cpuinfo_mips *c, unsigned int cpu)
 {
         decode_configs(c);
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_CAVIUM_CN38XX:
         case PRID_IMP_CAVIUM_CN31XX:
         case PRID_IMP_CAVIUM_CN30XX:
@@ -876,7 +878,7 @@ static inline void cpu_probe_ingenic(struct cpuinfo_mips *c, unsigned int cpu)
         decode_configs(c);
         /* JZRISC does not implement the CP0 counter. */
         c->options &= ~MIPS_CPU_COUNTER;
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_JZRISC:
                 c->cputype = CPU_JZRISC;
                 __cpu_name[cpu] = "Ingenic JZRISC";
@@ -891,7 +893,7 @@ static inline void cpu_probe_netlogic(struct cpuinfo_mips *c, int cpu)
 {
         decode_configs(c);
 
-        if ((c->processor_id & 0xff00) == PRID_IMP_NETLOGIC_AU13XX) {
+        if ((c->processor_id & PRID_IMP_MASK) == PRID_IMP_NETLOGIC_AU13XX) {
                 c->cputype = CPU_ALCHEMY;
                 __cpu_name[cpu] = "Au1300";
                 /* following stuff is not for Alchemy */
@@ -906,7 +908,7 @@ static inline void cpu_probe_netlogic(struct cpuinfo_mips *c, int cpu)
                         MIPS_CPU_EJTAG   |
                         MIPS_CPU_LLSC);
 
-        switch (c->processor_id & 0xff00) {
+        switch (c->processor_id & PRID_IMP_MASK) {
         case PRID_IMP_NETLOGIC_XLP2XX:
                 c->cputype = CPU_XLP;
                 __cpu_name[cpu] = "Broadcom XLPII";
@@ -985,7 +987,7 @@ void cpu_probe(void)
         c->cputype      = CPU_UNKNOWN;
 
         c->processor_id = read_c0_prid();
-        switch (c->processor_id & 0xff0000) {
+        switch (c->processor_id & PRID_COMP_MASK) {
         case PRID_COMP_LEGACY:
                 cpu_probe_legacy(c, cpu);
                 break;
diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 73ca8c52e83f..ae500ca76580 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -792,12 +792,12 @@ static inline void alias_74k_erratum(struct cpuinfo_mips *c)
          * aliases. In this case it is better to treat the cache as always
          * having aliases.
          */
-        if ((c->processor_id & 0xff) <= PRID_REV_ENCODE_332(2, 4, 0))
+        if ((c->processor_id & PRID_REV_MASK) <= PRID_REV_ENCODE_332(2, 4, 0))
                 c->dcache.flags |= MIPS_CACHE_VTAG;
-        if ((c->processor_id & 0xff) == PRID_REV_ENCODE_332(2, 4, 0))
+        if ((c->processor_id & PRID_REV_MASK) == PRID_REV_ENCODE_332(2, 4, 0))
                 write_c0_config6(read_c0_config6() | MIPS_CONF6_SYND);
-        if (((c->processor_id & 0xff00) == PRID_IMP_1074K) &&
-            ((c->processor_id & 0xff) <= PRID_REV_ENCODE_332(1, 1, 0))) {
+        if ((c->processor_id & PRID_IMP_MASK) == PRID_IMP_1074K &&
+            (c->processor_id & PRID_REV_MASK) <= PRID_REV_ENCODE_332(1, 1, 0)) {
                 c->dcache.flags |= MIPS_CACHE_VTAG;
                 write_c0_config6(read_c0_config6() | MIPS_CONF6_SYND);
         }
@@ -1031,7 +1031,8 @@ static void probe_pcache(void)
          * presumably no vendor is shipping his hardware in the "bad"
          * configuration.
          */
-        if ((prid & 0xff00) == PRID_IMP_R4000 && (prid & 0xff) < 0x40 &&
+        if ((prid & PRID_IMP_MASK) == PRID_IMP_R4000 &&
+            (prid & PRID_REV_MASK) < PRID_REV_R4400 &&
             !(config & CONF_SC) && c->icache.linesz != 16 &&
             PAGE_SIZE <= 0x8000)
                 panic("Improper R4000SC processor configuration detected");
diff --git a/arch/mips/mti-malta/malta-time.c b/arch/mips/mti-malta/malta-time.c
index 53aad4a35375..a18af5fce67e 100644
--- a/arch/mips/mti-malta/malta-time.c
+++ b/arch/mips/mti-malta/malta-time.c
@@ -27,6 +27,7 @@
 #include <linux/timex.h>
 #include <linux/mc146818rtc.h>
 
+#include <asm/cpu.h>
 #include <asm/mipsregs.h>
 #include <asm/mipsmtregs.h>
 #include <asm/hardirq.h>
@@ -76,7 +77,7 @@ static void __init estimate_frequencies(void)
 #endif
 
 #if defined (CONFIG_KVM_GUEST) && defined (CONFIG_KVM_HOST_FREQ)
-        unsigned int prid = read_c0_prid() & 0xffff00;
+        unsigned int prid = read_c0_prid() & (PRID_COMP_MASK | PRID_IMP_MASK);
 
         /*
          * XXXKYMA: hardwire the CPU frequency to Host Freq/4
@@ -169,7 +170,7 @@ unsigned int get_c0_compare_int(void)
 
 void __init plat_time_init(void)
 {
-        unsigned int prid = read_c0_prid() & 0xffff00;
+        unsigned int prid = read_c0_prid() & (PRID_COMP_MASK | PRID_IMP_MASK);
         unsigned int freq;
 
         estimate_frequencies();
diff --git a/arch/mips/mti-sead3/sead3-time.c b/arch/mips/mti-sead3/sead3-time.c
index a43ea3cc0a3b..552d26c34386 100644
--- a/arch/mips/mti-sead3/sead3-time.c
+++ b/arch/mips/mti-sead3/sead3-time.c
@@ -7,6 +7,7 @@
  */
 #include <linux/init.h>
 
+#include <asm/cpu.h>
 #include <asm/setup.h>
 #include <asm/time.h>
 #include <asm/irq.h>
@@ -34,7 +35,7 @@ static void __iomem *status_reg = (void __iomem *)0xbf000410;
  */
 static unsigned int __init estimate_cpu_frequency(void)
 {
-        unsigned int prid = read_c0_prid() & 0xffff00;
+        unsigned int prid = read_c0_prid() & (PRID_COMP_MASK | PRID_IMP_MASK);
         unsigned int tick = 0;
         unsigned int freq;
         unsigned int orig;
diff --git a/arch/mips/netlogic/xlr/fmn-config.c b/arch/mips/netlogic/xlr/fmn-config.c
index ed3bf0e3f309..c7622c6e5f67 100644
--- a/arch/mips/netlogic/xlr/fmn-config.c
+++ b/arch/mips/netlogic/xlr/fmn-config.c
@@ -36,6 +36,7 @@
 #include <linux/irq.h>
 #include <linux/interrupt.h>
 
+#include <asm/cpu.h>
 #include <asm/mipsregs.h>
 #include <asm/netlogic/xlr/fmn.h>
 #include <asm/netlogic/xlr/xlr.h>
@@ -187,7 +188,7 @@ void xlr_board_info_setup(void)
         int processor_id, num_core;
 
         num_core = hweight32(nlm_current_node()->coremask);
-        processor_id = read_c0_prid() & 0xff00;
+        processor_id = read_c0_prid() & PRID_IMP_MASK;
 
         setup_cpu_fmninfo(cpu, num_core);
         switch (processor_id) {
diff --git a/arch/mips/sibyte/bcm1480/setup.c b/arch/mips/sibyte/bcm1480/setup.c
index 05ed92c92b69..8e2e04f77870 100644
--- a/arch/mips/sibyte/bcm1480/setup.c
+++ b/arch/mips/sibyte/bcm1480/setup.c
@@ -22,6 +22,7 @@
 #include <linux/string.h>
 
 #include <asm/bootinfo.h>
+#include <asm/cpu.h>
 #include <asm/mipsregs.h>
 #include <asm/io.h>
 #include <asm/sibyte/sb1250.h>
@@ -119,7 +120,7 @@ void __init bcm1480_setup(void)
         uint64_t sys_rev;
         int plldiv;
 
-        sb1_pass = read_c0_prid() & 0xff;
+        sb1_pass = read_c0_prid() & PRID_REV_MASK;
         sys_rev = __raw_readq(IOADDR(A_SCD_SYSTEM_REVISION));
         soc_type = SYS_SOC_TYPE(sys_rev);
         part_type = G_SYS_PART(sys_rev);
diff --git a/arch/mips/sibyte/sb1250/setup.c b/arch/mips/sibyte/sb1250/setup.c
index a14bd4cb0bc0..3c02b2a77ae9 100644
--- a/arch/mips/sibyte/sb1250/setup.c
+++ b/arch/mips/sibyte/sb1250/setup.c
@@ -22,6 +22,7 @@
 #include <linux/string.h>
 
 #include <asm/bootinfo.h>
+#include <asm/cpu.h>
 #include <asm/mipsregs.h>
 #include <asm/io.h>
 #include <asm/sibyte/sb1250.h>
@@ -182,7 +183,7 @@ void __init sb1250_setup(void)
         int plldiv;
         int bad_config = 0;
 
-        sb1_pass = read_c0_prid() & 0xff;
+        sb1_pass = read_c0_prid() & PRID_REV_MASK;
         sys_rev = __raw_readq(IOADDR(A_SCD_SYSTEM_REVISION));
         soc_type = SYS_SOC_TYPE(sys_rev);
         soc_pass = G_SYS_REVISION(sys_rev);
diff --git a/arch/mips/sni/setup.c b/arch/mips/sni/setup.c
index 5b09b3544edd..efad85c8c823 100644
--- a/arch/mips/sni/setup.c
+++ b/arch/mips/sni/setup.c
@@ -25,6 +25,7 @@
 #endif
 
 #include <asm/bootinfo.h>
+#include <asm/cpu.h>
 #include <asm/io.h>
 #include <asm/reboot.h>
 #include <asm/sni.h>
@@ -173,7 +174,7 @@ void __init plat_mem_setup(void)
                 system_type = "RM300-Cxx";
                 break;
         case SNI_BRD_PCI_DESKTOP:
-                switch (read_c0_prid() & 0xff00) {
+                switch (read_c0_prid() & PRID_IMP_MASK) {
                 case PRID_IMP_R4600:
                 case PRID_IMP_R4700:
                         system_type = "RM200-C20";