FAILED: patch "[PATCH] riscv,mmio: Fix readX()-to-delay() ordering" failed to apply to 5.4-stable tree

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The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 4eb2eb1b4c0eb07793c240744843498564a67b83
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023081241-crisped-travesty-dcc8@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

4eb2eb1b4c0e ("riscv,mmio: Fix readX()-to-delay() ordering")
0c3ac28931d5 ("riscv: separate MMIO functions into their own header file")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 4eb2eb1b4c0eb07793c240744843498564a67b83 Mon Sep 17 00:00:00 2001
From: Andrea Parri <parri.andrea@xxxxxxxxx>
Date: Thu, 3 Aug 2023 06:27:38 +0200
Subject: [PATCH] riscv,mmio: Fix readX()-to-delay() ordering

Section 2.1 of the Platform Specification [1] states:

  Unless otherwise specified by a given I/O device, I/O devices are on
  ordering channel 0 (i.e., they are point-to-point strongly ordered).

which is not sufficient to guarantee that a readX() by a hart completes
before a subsequent delay() on the same hart (cf. memory-barriers.txt,
"Kernel I/O barrier effects").

Set the I(nput) bit in __io_ar() to restore the ordering, align inline
comments.

[1] https://github.com/riscv/riscv-platform-specs

Signed-off-by: Andrea Parri <parri.andrea@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230803042738.5937-1-parri.andrea@xxxxxxxxx
Fixes: fab957c11efe ("RISC-V: Atomic and Locking Code")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>

diff --git a/arch/riscv/include/asm/mmio.h b/arch/riscv/include/asm/mmio.h
index aff6c33ab0c0..4c58ee7f95ec 100644
--- a/arch/riscv/include/asm/mmio.h
+++ b/arch/riscv/include/asm/mmio.h
@@ -101,9 +101,9 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
  * Relaxed I/O memory access primitives. These follow the Device memory
  * ordering rules but do not guarantee any ordering relative to Normal memory
  * accesses.  These are defined to order the indicated access (either a read or
- * write) with all other I/O memory accesses. Since the platform specification
- * defines that all I/O regions are strongly ordered on channel 2, no explicit
- * fences are required to enforce this ordering.
+ * write) with all other I/O memory accesses to the same peripheral. Since the
+ * platform specification defines that all I/O regions are strongly ordered on
+ * channel 0, no explicit fences are required to enforce this ordering.
  */
 /* FIXME: These are now the same as asm-generic */
 #define __io_rbr()		do {} while (0)
@@ -125,14 +125,14 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
 #endif
 
 /*
- * 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.  The memory barriers here are necessary as RISC-V
+ * I/O memory access primitives.  Reads are ordered relative to any following
+ * Normal memory read and delay() loop.  Writes are ordered relative to any
+ * prior Normal memory write.  The memory barriers here are necessary as RISC-V
  * doesn't define any ordering between the memory space and the I/O space.
  */
 #define __io_br()	do {} while (0)
-#define __io_ar(v)	__asm__ __volatile__ ("fence i,r" : : : "memory")
-#define __io_bw()	__asm__ __volatile__ ("fence w,o" : : : "memory")
+#define __io_ar(v)	({ __asm__ __volatile__ ("fence i,ir" : : : "memory"); })
+#define __io_bw()	({ __asm__ __volatile__ ("fence w,o" : : : "memory"); })
 #define __io_aw()	mmiowb_set_pending()
 
 #define readb(c)	({ u8  __v; __io_br(); __v = readb_cpu(c); __io_ar(__v); __v; })




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