[4.2.y-ckt stable] Patch "stmmac: avoid ipq806x constant overflow warning" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    stmmac: avoid ipq806x constant overflow warning

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 3e8217d561cfbc9eddf5c47b61cfcfd119a09021 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd at arndb.de>
Date: Thu, 12 Nov 2015 22:03:40 +0100
Subject: stmmac: avoid ipq806x constant overflow warning

commit 49e4a2293035b420e807e739999d59c8ec1488e9 upstream.

Building dwmac-ipq806x on a 64-bit architecture produces a harmless
warning from gcc:

stmmac/dwmac-ipq806x.c: In function 'ipq806x_gmac_probe':
include/linux/bitops.h:6:19: warning: overflow in implicit constant conversion [-Woverflow]
  val = QSGMII_PHY_CDR_EN |
stmmac/dwmac-ipq806x.c:333:8: note: in expansion of macro 'QSGMII_PHY_CDR_EN'
 #define QSGMII_PHY_CDR_EN   BIT(0)
 #define BIT(nr)   (1UL << (nr))

This is a result of the type conversion rules in C, when we take the
logical OR of multiple different types. In particular, we have
and unsigned long

	QSGMII_PHY_CDR_EN == BIT(0) == (1ul << 0) == 0x0000000000000001ul

and a signed int

	0xC << QSGMII_PHY_TX_DRV_AMP_OFFSET == 0xc0000000

which together gives a signed long value

	0xffffffffc0000001l

and when this is passed into a function that takes an unsigned int type,
gcc warns about the signed overflow and the loss of the upper 32-bits that
are all ones.

This patch adds 'ul' type modifiers to the literal numbers passed in
here, so now the expression remains an 'unsigned long' with the upper
bits all zero, and that avoids the signed overflow and the warning.

Signed-off-by: Arnd Bergmann <arnd at arndb.de>
Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
index f0e4bb4..ae551f4 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
@@ -320,11 +320,11 @@ static void *ipq806x_gmac_setup(struct platform_device *pdev)
 			     QSGMII_PHY_RX_SIGNAL_DETECT_EN |
 			     QSGMII_PHY_TX_DRIVER_EN |
 			     QSGMII_PHY_QSGMII_EN |
-			     0x4 << QSGMII_PHY_PHASE_LOOP_GAIN_OFFSET |
-			     0x3 << QSGMII_PHY_RX_DC_BIAS_OFFSET |
-			     0x1 << QSGMII_PHY_RX_INPUT_EQU_OFFSET |
-			     0x2 << QSGMII_PHY_CDR_PI_SLEW_OFFSET |
-			     0xC << QSGMII_PHY_TX_DRV_AMP_OFFSET);
+			     0x4ul << QSGMII_PHY_PHASE_LOOP_GAIN_OFFSET |
+			     0x3ul << QSGMII_PHY_RX_DC_BIAS_OFFSET |
+			     0x1ul << QSGMII_PHY_RX_INPUT_EQU_OFFSET |
+			     0x2ul << QSGMII_PHY_CDR_PI_SLEW_OFFSET |
+			     0xCul << QSGMII_PHY_TX_DRV_AMP_OFFSET);
 	}

 	return gmac;
--
1.9.1