linux-kernel - [PATCH] openrisc: define arch-specific version of nop()

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Message-Id: <20260120-openrisc-nop-v1-1-a29da65537c8@redhat.com>
Date: Tue, 20 Jan 2026 12:07:23 -0500
From: Brian Masney <bmasney@...hat.com>
To: Jonas Bonn <jonas@...thpole.se>, 
 Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>, 
 Stafford Horne <shorne@...il.com>
Cc: linux-openrisc@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kernel test robot <lkp@...el.com>, Brian Masney <bmasney@...hat.com>
Subject: [PATCH] openrisc: define arch-specific version of nop()

When compiling a driver written for MIPS on OpenRISC that uses the nop()
function, it fails due to the following error:

    drivers/watchdog/pic32-wdt.c: Assembler messages:
    drivers/watchdog/pic32-wdt.c:125: Error: unrecognized instruction `nop'

The driver currently uses the generic version of nop() from
include/asm-generic/barrier.h:

    #ifndef nop
    #define nop()   asm volatile ("nop")
    #endif

Let's fix this on OpenRISC by defining an architecture-specific version
of nop().

This was tested by performing an allmodconfig openrisc cross compile on
an aarch64 host.

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601180236.BVy480We-lkp@intel.com/
Signed-off-by: Brian Masney <bmasney@...hat.com>
---
 arch/openrisc/include/asm/barrier.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/openrisc/include/asm/barrier.h b/arch/openrisc/include/asm/barrier.h
index 7538294721bed7bc8da3d08f3db89a408091f3f8..8e592c99090235423a9f4c9149da9822918afb13 100644
--- a/arch/openrisc/include/asm/barrier.h
+++ b/arch/openrisc/include/asm/barrier.h
@@ -4,6 +4,8 @@
 
 #define mb() asm volatile ("l.msync" ::: "memory")
 
+#define nop() asm volatile ("l.nop")
+
 #include <asm-generic/barrier.h>
 
 #endif /* __ASM_BARRIER_H */

---
base-commit: d08c85ac8894995d4b0d8fb48d2f6a3e53cd79ab
change-id: 20260120-openrisc-nop-82b7f95dad7f

Best regards,
-- 
Brian Masney <bmasney@...hat.com>