linux-kernel - [PATCH 1/2] riscv: fix detection of toolchain Zicbom support

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Date:   Thu,  6 Oct 2022 18:35:20 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Palmer Dabbelt <palmer@...belt.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Tom Rix <trix@...hat.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Dao Lu <daolu@...osinc.com>, Heiko Stuebner <heiko@...ech.de>,
        Guo Ren <guoren@...nel.org>, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Kevin Hilman <khilman@...libre.com>
Subject: [PATCH 1/2] riscv: fix detection of toolchain Zicbom support

From: Conor Dooley <conor.dooley@...rochip.com>

It is not sufficient to check if a toolchain supports a particular
extension without checking if the linker supports that extension too.
For example, Clang 15 supports Zicbom but GNU bintutils 2.35.2 does
not, leading build errors like so:

riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_c2p0_zicbom1p0_zihintpause2p0: Invalid or unknown z ISA extension: 'zicbom'

Convert CC_HAS_ZICBOM to TOOLCHAIN_HAS_ZICBOM & check if the linker
also supports Zicbom.

Reported-by: Kevin Hilman <khilman@...libre.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1714
Link: https://storage.kernelci.org/next/master/next-20220920/riscv/defconfig+CONFIG_EFI=n/clang-16/logs/kernel.log
Fixes: 1631ba1259d6 ("riscv: Add support for non-coherent devices using zicbom extension")
Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
---
 arch/riscv/Kconfig  | 10 ++++++----
 arch/riscv/Makefile |  3 +--
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index d557cc50295d..6da36553158b 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -401,14 +401,16 @@ config RISCV_ISA_SVPBMT
 
 	   If you don't know what to do here, say Y.
 
-config CC_HAS_ZICBOM
+config TOOLCHAIN_HAS_ZICBOM
 	bool
-	default y if 64BIT && $(cc-option,-mabi=lp64 -march=rv64ima_zicbom)
-	default y if 32BIT && $(cc-option,-mabi=ilp32 -march=rv32ima_zicbom)
+	default y
+	depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zicbom)
+	depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zicbom)
+	depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
 
 config RISCV_ISA_ZICBOM
 	bool "Zicbom extension support for non-coherent DMA operation"
-	depends on CC_HAS_ZICBOM
+	depends on TOOLCHAIN_HAS_ZICBOM
 	depends on !XIP_KERNEL && MMU
 	select RISCV_DMA_NONCOHERENT
 	select RISCV_ALTERNATIVE
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 3fa8ef336822..3607d38edb4f 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -57,8 +57,7 @@ toolchain-need-zicsr-zifencei := $(call cc-option-yn, -march=$(riscv-march-y)_zi
 riscv-march-$(toolchain-need-zicsr-zifencei) := $(riscv-march-y)_zicsr_zifencei
 
 # Check if the toolchain supports Zicbom extension
-toolchain-supports-zicbom := $(call cc-option-yn, -march=$(riscv-march-y)_zicbom)
-riscv-march-$(toolchain-supports-zicbom) := $(riscv-march-y)_zicbom
+riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZICBOM) := $(riscv-march-y)_zicbom
 
 # Check if the toolchain supports Zihintpause extension
 toolchain-supports-zihintpause := $(call cc-option-yn, -march=$(riscv-march-y)_zihintpause)
-- 
2.37.3