1 files changed, 39 insertions, 0 deletions
diff --git a/arch/x86/include/asm/processor-cyrix.h b/arch/x86/include/asm/processor-cyrix.h
new file mode 100644
index 000000000..aaedd73ea
--- /dev/null
+++ b/arch/x86/include/asm/processor-cyrix.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * NSC/Cyrix CPU indexed register access. Must be inlined instead of
+ * macros to ensure correct access ordering
+ * Access order is always 0x22 (=offset), 0x23 (=value)
+ *
+ * When using the old macros a line like
+ *   setCx86(CX86_CCR2, getCx86(CX86_CCR2) | 0x88);
+ * gets expanded to:
+ *  do {
+ *    outb((CX86_CCR2), 0x22);
+ *    outb((({
+ *        outb((CX86_CCR2), 0x22);
+ *        inb(0x23);
+ *    }) | 0x88), 0x23);
+ *  } while (0);
+ *
+ * which in fact violates the access order (= 0x22, 0x22, 0x23, 0x23).
+ */
+
+static inline u8 getCx86(u8 reg)
+{
+	outb(reg, 0x22);
+	return inb(0x23);
+}
+
+static inline void setCx86(u8 reg, u8 data)
+{
+	outb(reg, 0x22);
+	outb(data, 0x23);
+}
+
+#define getCx86_old(reg) ({ outb((reg), 0x22); inb(0x23); })
+
+#define setCx86_old(reg, data) do { \
+	outb((reg), 0x22); \
+	outb((data), 0x23); \
+} while (0)
+