[U-Boot] [PATCH] i2c: mvtwsi: avoid writing to twsi_control_flags prior to relocation

[Chris Packham]

In a system where the initial u-boot location is genuinely NOR flash (as
opposed to RAM or a cache-line setup by a pre-bootloader) writes to the
data section are problematic. At best these writes have no effect at
worse they put the flash memory into a status mode which changes the
executable code underneath us.

Only write to twsi_control_flags once we know we've relocated to RAM.

Signed-off-by: Chris Packham <judge.packham at gmail.com>
---

 drivers/i2c/mvtwsi.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/mvtwsi.c b/drivers/i2c/mvtwsi.c
index 221ff4f..aee28c4 100644
--- a/drivers/i2c/mvtwsi.c
+++ b/drivers/i2c/mvtwsi.c
@@ -28,6 +28,8 @@
 #error Driver mvtwsi not supported by SoC or board
 #endif
 
+DECLARE_GLOBAL_DATA_PTR;
+
 /*
  * TWSI register structure
  */
@@ -297,7 +299,8 @@ static void twsi_reset(struct i2c_adapter *adap)
 {
 	struct mvtwsi_registers *twsi = twsi_get_base(adap);
 	/* ensure controller will be enabled by any twsi*() function */
-	twsi_control_flags = MVTWSI_CONTROL_TWSIEN;
+	if (gd->flags & GD_FLG_RELOC)
+		twsi_control_flags = MVTWSI_CONTROL_TWSIEN;
 	/* reset controller */
 	writel(0, &twsi->soft_reset);
 	/* wait 2 ms -- this is what the Marvell LSP does */
-- 
2.8.2