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

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Message-Id: <1522933753-19589-1-git-send-email-okaya@codeaurora.org>
Date:   Thu,  5 Apr 2018 09:09:09 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     arnd@...db.de, timur@...eaurora.org, sulrich@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Sinan Kaya <okaya@...eaurora.org>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 1/5] io: define several IO & PIO barrier types for the asm-generic version

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@...eaurora.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