The first 0x54 core were 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 <[email protected]>
---
arch/arc/include/asm/arcregs.h | 8 ++++++++
arch/arc/kernel/setup.c | 26 +++++++++++++++++++++-----
2 files changed, 29 insertions(+), 5 deletions(-)
diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index f1b86cef0905..a27eafdc8260 100644
--- 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 93d4d6639873..7b2340996cf8 100644
--- 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);
+
+ }
}
}
--
2.7.4