ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 95 insertions, 0 deletions

diff --git a/include/asm-generic/iomap.h b/include/asm-generic/iomap.h
new file mode 100644
index 000000000..9f3f25d7f
--- /dev/null
+++ b/include/asm-generic/iomap.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __GENERIC_IO_H
+#define __GENERIC_IO_H
+
+#include <linux/linkage.h>
+#include <asm/byteorder.h>
+
+/*
+ * These are the "generic" interfaces for doing new-style
+ * memory-mapped or PIO accesses. Architectures may do
+ * their own arch-optimized versions, these just act as
+ * wrappers around the old-style IO register access functions:
+ * read[bwl]/write[bwl]/in[bwl]/out[bwl]
+ *
+ * Don't include this directly, include it from <asm/io.h>.
+ */
+
+/*
+ * Read/write from/to an (offsettable) iomem cookie. It might be a PIO
+ * access or a MMIO access, these functions don't care. The info is
+ * encoded in the hardware mapping set up by the mapping functions
+ * (or the cookie itself, depending on implementation and hw).
+ *
+ * The generic routines just encode the PIO/MMIO as part of the
+ * cookie, and coldly assume that the MMIO IO mappings are not
+ * in the low address range. Architectures for which this is not
+ * true can't use this generic implementation.
+ */
+extern unsigned int ioread8(const void __iomem *);
+extern unsigned int ioread16(const void __iomem *);
+extern unsigned int ioread16be(const void __iomem *);
+extern unsigned int ioread32(const void __iomem *);
+extern unsigned int ioread32be(const void __iomem *);
+
+extern u64 __ioread64_lo_hi(const void __iomem *addr);
+extern u64 __ioread64_hi_lo(const void __iomem *addr);
+extern u64 __ioread64be_lo_hi(const void __iomem *addr);
+extern u64 __ioread64be_hi_lo(const void __iomem *addr);
+
+extern void iowrite8(u8, void __iomem *);
+extern void iowrite16(u16, void __iomem *);
+extern void iowrite16be(u16, void __iomem *);
+extern void iowrite32(u32, void __iomem *);
+extern void iowrite32be(u32, void __iomem *);
+
+extern void __iowrite64_lo_hi(u64 val, void __iomem *addr);
+extern void __iowrite64_hi_lo(u64 val, void __iomem *addr);
+extern void __iowrite64be_lo_hi(u64 val, void __iomem *addr);
+extern void __iowrite64be_hi_lo(u64 val, void __iomem *addr);
+
+/*
+ * "string" versions of the above. Note that they
+ * use native byte ordering for the accesses (on
+ * the assumption that IO and memory agree on a
+ * byte order, and CPU byteorder is irrelevant).
+ *
+ * They do _not_ update the port address. If you
+ * want MMIO that copies stuff laid out in MMIO
+ * memory across multiple ports, use "memcpy_toio()"
+ * and friends.
+ */
+extern void ioread8_rep(const void __iomem *port, void *buf, unsigned long count);
+extern void ioread16_rep(const void __iomem *port, void *buf, unsigned long count);
+extern void ioread32_rep(const void __iomem *port, void *buf, unsigned long count);
+
+extern void iowrite8_rep(void __iomem *port, const void *buf, unsigned long count);
+extern void iowrite16_rep(void __iomem *port, const void *buf, unsigned long count);
+extern void iowrite32_rep(void __iomem *port, const void *buf, unsigned long count);
+
+#ifdef CONFIG_HAS_IOPORT_MAP
+/* Create a virtual mapping cookie for an IO port range */
+extern void __iomem *ioport_map(unsigned long port, unsigned int nr);
+extern void ioport_unmap(void __iomem *);
+#endif
+
+#ifndef ioremap_wc
+#define ioremap_wc ioremap
+#endif
+
+#ifndef ioremap_wt
+#define ioremap_wt ioremap
+#endif
+
+#ifndef ioremap_np
+/* See the comment in asm-generic/io.h about ioremap_np(). */
+#define ioremap_np ioremap_np
+static inline void __iomem *ioremap_np(phys_addr_t offset, size_t size)
+{
+	return NULL;
+}
+#endif
+
+#include <asm-generic/pci_iomap.h>
+
+#endif