Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/csky/include/asm/io.h b/arch/csky/include/asm/io.h
new file mode 100644
index 0000000..80d071e
--- /dev/null
+++ b/arch/csky/include/asm/io.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#ifndef __ASM_CSKY_IO_H
+#define __ASM_CSKY_IO_H
+
+#include <asm/pgtable.h>
+#include <linux/types.h>
+#include <linux/version.h>
+
+/*
+ * I/O memory access primitives. Reads are ordered relative to any
+ * following Normal memory access. Writes are ordered relative to any prior
+ * Normal memory access.
+ *
+ * For CACHEV1 (807, 810), store instruction could fast retire, so we need
+ * another mb() to prevent st fast retire.
+ *
+ * For CACHEV2 (860), store instruction with PAGE_ATTR_NO_BUFFERABLE won't
+ * fast retire.
+ */
+#define readb(c) ({ u8 __v = readb_relaxed(c); rmb(); __v; })
+#define readw(c) ({ u16 __v = readw_relaxed(c); rmb(); __v; })
+#define readl(c) ({ u32 __v = readl_relaxed(c); rmb(); __v; })
+
+#ifdef CONFIG_CPU_HAS_CACHEV2
+#define writeb(v,c) ({ wmb(); writeb_relaxed((v),(c)); })
+#define writew(v,c) ({ wmb(); writew_relaxed((v),(c)); })
+#define writel(v,c) ({ wmb(); writel_relaxed((v),(c)); })
+#else
+#define writeb(v,c) ({ wmb(); writeb_relaxed((v),(c)); mb(); })
+#define writew(v,c) ({ wmb(); writew_relaxed((v),(c)); mb(); })
+#define writel(v,c) ({ wmb(); writel_relaxed((v),(c)); mb(); })
+#endif
+
+/*
+ * I/O memory mapping functions.
+ */
+extern void __iomem *ioremap_cache(phys_addr_t addr, size_t size);
+extern void __iomem *__ioremap(phys_addr_t addr, size_t size, pgprot_t prot);
+extern void iounmap(void *addr);
+
+#define ioremap(addr, size) __ioremap((addr), (size), pgprot_noncached(PAGE_KERNEL))
+#define ioremap_wc(addr, size) __ioremap((addr), (size), pgprot_writecombine(PAGE_KERNEL))
+#define ioremap_nocache(addr, size) ioremap((addr), (size))
+#define ioremap_cache ioremap_cache
+
+#include <asm-generic/io.h>
+
+#endif /* __ASM_CSKY_IO_H */