[PATCH 4.4 13/37] irda: fix overly long udelay()

From: Greg Kroah-Hartman
Date: Tue Jun 05 2018 - 13:29:16 EST

4.4-stable review patch. If anyone has any objections, please let me know.


From: Arnd Bergmann <arnd@xxxxxxxx>

commit c9bd28233b6d0d82ac3ba0215723be0a8262c39c upstream.

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@xxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/net/irda/w83977af_ir.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- 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(st

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 */