linux-kernel - [PATCH v2] MTD: Fix Orion NAND driver compilation with ARM OABI

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Message-ID: <20100325152505.17612.40158.stgit@pauliusz>
Date:	Thu, 25 Mar 2010 17:25:05 +0200
From:	Paulius Zaleckas <paulius.zaleckas@...il.com>
To:	dwmw2@...radead.org
Cc:	nico@...xnic.net, akpm@...ux-foundation.org,
	u.kleine-koenig@...gutronix.de, simon.kagstrom@...insight.net,
	linux-mtd@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] MTD: Fix Orion NAND driver compilation with ARM OABI

We must tell GCC to use even register for variable passed
to ldrd instruction. Without this patch GCC 4.2.1 puts this
variable to r2/r3 on EABI and r3/r4 on OABI, so force it to
r2/r3. This does not change anything when EABI and OABI
compilation works OK.

Without this patch and with OABI I get:
  CC      drivers/mtd/nand/orion_nand.o
/tmp/ccMkwOCs.s: Assembler messages:
/tmp/ccMkwOCs.s:63: Error: first destination register must be even -- `ldrd r3,[ip]'
make[5]: *** [drivers/mtd/nand/orion_nand.o] Error 1

Signed-off-by: Paulius Zaleckas <paulius.zaleckas@...il.com>
---

 drivers/mtd/nand/orion_nand.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/drivers/mtd/nand/orion_nand.c b/drivers/mtd/nand/orion_nand.c
index f59c074..d60fc57 100644
--- a/drivers/mtd/nand/orion_nand.c
+++ b/drivers/mtd/nand/orion_nand.c
@@ -60,7 +60,13 @@ static void orion_nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
 	}
 	buf64 = (uint64_t *)buf;
 	while (i < len/8) {
-		uint64_t x;
+		/*
+		 * Since GCC has no proper constraint (PR 43518)
+		 * force x variable to r2/r3 registers as ldrd instruction
+		 * requires first register to be even.
+		 */
+		register uint64_t x asm ("r2");
+
 		asm volatile ("ldrd\t%0, [%1]" : "=&r" (x) : "r" (io_base));
 		buf64[i++] = x;
 	}

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