linux-kernel - [PATCH] riscv: keep 32-bit kernel to 32-bit phys_addr

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Message-Id: <20200106231611.10169-1-olof@lixom.net>
Date:   Mon,  6 Jan 2020 15:16:11 -0800
From:   Olof Johansson <olof@...om.net>
To:     paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Olof Johansson <olof@...om.net>
Subject: [PATCH] riscv: keep 32-bit kernel to 32-bit phys_addr_t

While rv32 technically has 34-bit physical addresses, no current
platforms use it and it's likely to shake out driver bugs.

Let's keep 64-bit phys_addr_t off on 32-bit builds until one shows up,
since other work will be needed to make such a system useful anyway.

Signed-off-by: Olof Johansson <olof@...om.net>
---
 arch/riscv/Kconfig | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a31169b02ec06..33a20fa046e0a 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -12,8 +12,9 @@ config 32BIT
 
 config RISCV
 	def_bool y
-	# even on 32-bit, physical (and DMA) addresses are > 32-bits
-	select PHYS_ADDR_T_64BIT
+	# While RV32 has 34-bit physical addresses, no known platform
+	# uses it, so keep it to 32-bit until one shows up to test with.
+	select PHYS_ADDR_T_64BIT if 64BIT
 	select OF
 	select OF_EARLY_FLATTREE
 	select OF_IRQ
-- 
2.20.1