[added,to,the,4.1,stable,tree] irda: fix overly long udelay()

Message ID 20180118205908.3220-293-alexander.levin@microsoft.com
State New
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  • [added,to,the,4.1,stable,tree] irda: fix overly long udelay()
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Commit Message

Sasha Levin Jan. 18, 2018, 9:02 p.m.
From: Arnd Bergmann <arnd@arndb.de>

This patch has been added to the  stable tree. If you have any
objections, please let us know.




[ Upstream commit c9bd28233b6d0d82ac3ba0215723be0a8262c39c ]

irda_get_mtt() returns a hardcoded '10000' in some cases,
and with gcc-7, we get a build error because this triggers a
compile-time check in udelay():

drivers/net/irda/w83977af_ir.o: In function `w83977af_hard_xmit':
w83977af_ir.c:(.text.w83977af_hard_xmit+0x14c): undefined reference to `__bad_udelay'

Older compilers did not run into this because they either did not
completely inline the irda_get_mtt() or did not consider the
10000 value a constant expression.

The code has been wrong since the start of git history.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
 drivers/net/irda/w83977af_ir.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/irda/w83977af_ir.c b/drivers/net/irda/w83977af_ir.c
index 4e3d2e7c697c..e8c3a8c32534 100644
--- a/drivers/net/irda/w83977af_ir.c
+++ b/drivers/net/irda/w83977af_ir.c
@@ -518,7 +518,9 @@  static netdev_tx_t w83977af_hard_xmit(struct sk_buff *skb,
 		mtt = irda_get_mtt(skb);
 		pr_debug("%s(%ld), mtt=%d\n", __func__ , jiffies, mtt);
-			if (mtt)
+			if (mtt > 1000)
+				mdelay(mtt/1000);
+			else if (mtt)
 			/* Enable DMA interrupt */