[PATCH v4 1/5] io: define several IO & PIO barrier types for the asm-generic version

Sinan Kaya
2018-04-05T13:09:22Z

Getting ready to harden readX()/writeX() and inX()/outX() semantics for the
generic implementation.

Defining two set of macros as __io_br() and __io_ar() to indicate actions
to be taken before and after MMIO read.

Defining two set of macros as __io_bw() and __io_aw() to indicate actions
to be taken before and after MMIO write.

Defining two set of macros as __io_pbw() and __io_paw() to indicate actions
to be taken before and after Port IO write.

Defining two set of macros as __io_pbr() and __io_par() to indicate actions
to be taken before and after Port IO read.

If rmb() is available for the architecture, prefer rmb() as the default
implementation of __io_ar()/__io_par().

If wmb() is available for the architecture, prefer wmb() as the default
implementation of __io_bw()/__io_pbw().

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
---
include/asm-generic/io.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index b4531e3..570433b 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -25,6 +25,50 @@
#define mmiowb() do {} while (0)
#endif

+#ifndef __io_br
+#define __io_br() barrier()
+#endif
+
+/* prevent prefetching of coherent DMA data ahead of a dma-complete */
+#ifndef __io_ar
+#ifdef rmb
+#define __io_ar() rmb()
+#else
+#define __io_ar() barrier()
+#endif
+#endif
+
+/* flush writes to coherent DMA data before possibly triggering a DMA read */
+#ifndef __io_bw
+#ifdef wmb
+#define __io_bw() wmb()
+#else
+#define __io_bw() barrier()
+#endif
+#endif
+
+/* serialize device access against a spin_unlock, usually handled there. */
+#ifndef __io_aw
+#define __io_aw() barrier()
+#endif
+
+#ifndef __io_pbw
+#define __io_pbw() __io_bw()
+#endif
+
+#ifndef __io_paw
+#define __io_paw() __io_aw()
+#endif
+
+#ifndef __io_pbr
+#define __io_pbr() __io_br()
+#endif
+
+#ifndef __io_par
+#define __io_par() __io_ar()
+#endif
+
+
/*
* __raw_{read,write}{b,w,l,q}() access memory in native endianness.
*
--
2.7.4