ARM: 6294/1: etm: do a dummy read from OSSRR during initialization

The first read from ETM OS save and restore register after the power
down bit deassertion returns garbage.

Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Alexander Shishkin <virtuoso@slind.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/arm/kernel/etm.c b/arch/arm/kernel/etm.c
index 9e9db63c298a..56418f98cd01 100644
--- a/arch/arm/kernel/etm.c
+++ b/arch/arm/kernel/etm.c
@@ -543,7 +543,9 @@ static int __init etm_probe(struct amba_device *dev, struct amba_id *id)
         t->etm_portsz = 1;
 
         etm_unlock(t);
-        ret = etm_readl(t, ETMMR_PDSR);
+        (void)etm_readl(t, ETMMR_PDSR);
+        /* dummy first read */
+        (void)etm_readl(&tracer, ETMMR_OSSRR);
 
         t->ncmppairs = etm_readl(t, ETMR_CONFCODE) & 0xf;
         etm_writel(t, 0x440, ETMR_CTRL);