ARCv2: don't assume core 0x54 has dual issue

The first release of core4 (0x54) was dual issue only (HS4x).
Newer releases allow hardware to be configured as single issue (HS3x)
or dual issue.

Prevent accessing a HS4x only aux register in HS3x, which otherwise
leads to illegal instruction exceptions

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index f1b86cef09057ace18085cb1cb3f18b3be274852..a27eafdc82602f6856b00c5fbd82db72c33cf238 100644 (file)
--- a/arch/arc/include/asm/arcregs.h
+++ b/arch/arc/include/asm/arcregs.h
@@ -151,6 +151,14 @@ struct bcr_isa_arcv2 {
 #endif
 };
 
+struct bcr_uarch_build_arcv2 {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+       unsigned int pad:8, prod:8, maj:8, min:8;
+#else
+       unsigned int min:8, maj:8, prod:8, pad:8;
+#endif
+};
+
 struct bcr_mpy {
 #ifdef CONFIG_CPU_BIG_ENDIAN
        unsigned int pad:8, x1616:8, dsp:4, cycles:2, type:2, ver:8;

diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index 93d4d663987373080c32555ad8efb351c5542962..7b2340996cf80fc4ddc382c55d86acbe37d49bf5 100644 (file)
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -199,13 +199,29 @@ static void read_arc_build_cfg_regs(void)
                cpu->bpu.ret_stk = 4 << bpu.rse;
 
                if (cpu->core.family >= 0x54) {
-                       unsigned int exec_ctrl;
 
-                       READ_BCR(AUX_EXEC_CTRL, exec_ctrl);
-                       cpu->extn.dual_enb = !(exec_ctrl & 1);
+                       struct bcr_uarch_build_arcv2 uarch;
 
-                       /* dual issue always present for this core */
-                       cpu->extn.dual = 1;
+                       /*
+                        * The first 0x54 core (uarch maj:min 0:1 or 0:2) was
+                        * dual issue only (HS4x). But next uarch rev (1:0)
+                        * allows it be configured for single issue (HS3x)
+                        * Ensure we fiddle with dual issue only on HS4x
+                        */
+                       READ_BCR(ARC_REG_MICRO_ARCH_BCR, uarch);
+
+                       if (uarch.prod == 4) {
+                               unsigned int exec_ctrl;
+
+                               /* dual issue hardware always present */
+                               cpu->extn.dual = 1;
+
+                               READ_BCR(AUX_EXEC_CTRL, exec_ctrl);
+
+                               /* dual issue hardware enabled ? */
+                               cpu->extn.dual_enb = !(exec_ctrl & 1);
+
+                       }
                }
        }