[PATCH] stmmac: avoid ipq806x constant overflow warning

[PATCH] stmmac: avoid ipq806x constant overflow warning

[Arnd Bergmann]

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))

The compiler warns about the fact that a 64-bit literal is passed
into a function that takes a 32-bit argument. I could not fully understand
why it warns despite the fact that this number is always small enough
to fit, but changing the use of BIT() macros into the equivalent hexadecimal
representation avoids the warning

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")
---
This came up on the arm64 allmodconfig build

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
index 9d89bdbf029f..4abd9b0b542a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
@@ -77,11 +77,11 @@
 /* Only GMAC1/2/3 support SGMII and their CTL register are not contiguous */
 #define QSGMII_PHY_SGMII_CTL(x)			((x == 1) ? 0x134 : \
 						 (0x13c + (4 * (x - 2))))
-#define QSGMII_PHY_CDR_EN			BIT(0)
-#define QSGMII_PHY_RX_FRONT_EN			BIT(1)
-#define QSGMII_PHY_RX_SIGNAL_DETECT_EN		BIT(2)
-#define QSGMII_PHY_TX_DRIVER_EN			BIT(3)
-#define QSGMII_PHY_QSGMII_EN			BIT(7)
+#define QSGMII_PHY_CDR_EN			0x01u
+#define QSGMII_PHY_RX_FRONT_EN			0x02u
+#define QSGMII_PHY_RX_SIGNAL_DETECT_EN		0x04u
+#define QSGMII_PHY_TX_DRIVER_EN			0x08u
+#define QSGMII_PHY_QSGMII_EN			0x80u
 #define QSGMII_PHY_PHASE_LOOP_GAIN_OFFSET	12
 #define QSGMII_PHY_PHASE_LOOP_GAIN_MASK		0x7
 #define QSGMII_PHY_RX_DC_BIAS_OFFSET		18

[PATCH] stmmac: avoid ipq806x constant overflow warning

[Arnd Bergmann]

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))

The compiler warns about the fact that a 64-bit literal is passed
into a function that takes a 32-bit argument. I could not fully understand
why it warns despite the fact that this number is always small enough
to fit, but changing the use of BIT() macros into the equivalent hexadecimal
representation avoids the warning

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")
---
This came up on the arm64 allmodconfig build

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
index 9d89bdbf029f..4abd9b0b542a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
@@ -77,11 +77,11 @@
 /* Only GMAC1/2/3 support SGMII and their CTL register are not contiguous */
 #define QSGMII_PHY_SGMII_CTL(x)			((x == 1) ? 0x134 : \
 						 (0x13c + (4 * (x - 2))))
-#define QSGMII_PHY_CDR_EN			BIT(0)
-#define QSGMII_PHY_RX_FRONT_EN			BIT(1)
-#define QSGMII_PHY_RX_SIGNAL_DETECT_EN		BIT(2)
-#define QSGMII_PHY_TX_DRIVER_EN			BIT(3)
-#define QSGMII_PHY_QSGMII_EN			BIT(7)
+#define QSGMII_PHY_CDR_EN			0x01u
+#define QSGMII_PHY_RX_FRONT_EN			0x02u
+#define QSGMII_PHY_RX_SIGNAL_DETECT_EN		0x04u
+#define QSGMII_PHY_TX_DRIVER_EN			0x08u
+#define QSGMII_PHY_QSGMII_EN			0x80u
 #define QSGMII_PHY_PHASE_LOOP_GAIN_OFFSET	12
 #define QSGMII_PHY_PHASE_LOOP_GAIN_MASK		0x7
 #define QSGMII_PHY_RX_DC_BIAS_OFFSET		18

Re: [PATCH] stmmac: avoid ipq806x constant overflow warning

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 12 Nov 2015 15:12:48 +0100

> 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))
> 
> The compiler warns about the fact that a 64-bit literal is passed
> into a function that takes a 32-bit argument. I could not fully understand
> why it warns despite the fact that this number is always small enough
> to fit, but changing the use of BIT() macros into the equivalent hexadecimal
> representation avoids the warning
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")

I've seen this warning too on x86_64 and had been meaning to look
into it, thanks for taking the initiative. :)

Moving away from using BIT() is somewhat disappointing, because we
want to encourage people to use these macros.

I think it's also easier from a driver author and auditing
perspective, you can see that something is being defined as bit X and
then check the documentation for the chip to see if bit X is correct
or not.

With the hex values there is more mental work and room for... mistakes.

Also I don't even understand the compiler's behavior, it's warning
about QSGMII_PHY_CDR_EN but if you define only that to "0x1u" it still
warns about QSGMII_PHY_CDR_EN.

The warning goes away only if you change all 5 BIT() uses.

This makes me like the change even less, something foul is going on
here and I'd rather figure out what that is than install this patch.

Thanks.

[PATCH] stmmac: avoid ipq806x constant overflow warning

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 12 Nov 2015 15:12:48 +0100

> 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))
> 
> The compiler warns about the fact that a 64-bit literal is passed
> into a function that takes a 32-bit argument. I could not fully understand
> why it warns despite the fact that this number is always small enough
> to fit, but changing the use of BIT() macros into the equivalent hexadecimal
> representation avoids the warning
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")

I've seen this warning too on x86_64 and had been meaning to look
into it, thanks for taking the initiative. :)

Moving away from using BIT() is somewhat disappointing, because we
want to encourage people to use these macros.

I think it's also easier from a driver author and auditing
perspective, you can see that something is being defined as bit X and
then check the documentation for the chip to see if bit X is correct
or not.

With the hex values there is more mental work and room for... mistakes.

Also I don't even understand the compiler's behavior, it's warning
about QSGMII_PHY_CDR_EN but if you define only that to "0x1u" it still
warns about QSGMII_PHY_CDR_EN.

The warning goes away only if you change all 5 BIT() uses.

This makes me like the change even less, something foul is going on
here and I'd rather figure out what that is than install this patch.

Thanks.

Re: [PATCH] stmmac: avoid ipq806x constant overflow warning

[Arnd Bergmann]

On Thursday 12 November 2015 12:25:28 David Miller wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> Date: Thu, 12 Nov 2015 15:12:48 +0100
> 
> > 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))
> > 
> > The compiler warns about the fact that a 64-bit literal is passed
> > into a function that takes a 32-bit argument. I could not fully understand
> > why it warns despite the fact that this number is always small enough
> > to fit, but changing the use of BIT() macros into the equivalent hexadecimal
> > representation avoids the warning
> > 
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")
> 
> I've seen this warning too on x86_64 and had been meaning to look
> into it, thanks for taking the initiative. 
> 
> Moving away from using BIT() is somewhat disappointing, because we
> want to encourage people to use these macros.

Ok, I never really liked that macro, so I didn't mind removing it. ;-)

I spent too much time working at IBM where all internal documentation
uses bit numbers that call the MSB bit 0, and drivers use randomly
either the IBM notation or the one that everyone else uses, so I always
found the hex numbers way more intuitive.

> Also I don't even understand the compiler's behavior, it's warning
> about QSGMII_PHY_CDR_EN but if you define only that to "0x1u" it still
> warns about QSGMII_PHY_CDR_EN.
> 
> The warning goes away only if you change all 5 BIT() uses.

Yes, I have spent the time to analyze the problem now and it all makes
sense. A proper patch follows.

	Arnd

[PATCH] stmmac: avoid ipq806x constant overflow warning

[Arnd Bergmann]

On Thursday 12 November 2015 12:25:28 David Miller wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> Date: Thu, 12 Nov 2015 15:12:48 +0100
> 
> > 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))
> > 
> > The compiler warns about the fact that a 64-bit literal is passed
> > into a function that takes a 32-bit argument. I could not fully understand
> > why it warns despite the fact that this number is always small enough
> > to fit, but changing the use of BIT() macros into the equivalent hexadecimal
> > representation avoids the warning
> > 
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")
> 
> I've seen this warning too on x86_64 and had been meaning to look
> into it, thanks for taking the initiative. 
> 
> Moving away from using BIT() is somewhat disappointing, because we
> want to encourage people to use these macros.

Ok, I never really liked that macro, so I didn't mind removing it. ;-)

I spent too much time working at IBM where all internal documentation
uses bit numbers that call the MSB bit 0, and drivers use randomly
either the IBM notation or the one that everyone else uses, so I always
found the hex numbers way more intuitive.

> Also I don't even understand the compiler's behavior, it's warning
> about QSGMII_PHY_CDR_EN but if you define only that to "0x1u" it still
> warns about QSGMII_PHY_CDR_EN.
> 
> The warning goes away only if you change all 5 BIT() uses.

Yes, I have spent the time to analyze the problem now and it all makes
sense. A proper patch follows.

	Arnd

[PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Arnd Bergmann]

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@arndb.de>
Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
index 9d89bdbf029f..82de68b1a452 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
@@ -337,11 +337,11 @@ static int ipq806x_gmac_probe(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);
 	}
 
 	plat_dat->has_gmac = true;

[PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Arnd Bergmann]

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@arndb.de>
Fixes: b1c17215d718 ("stmmac: add ipq806x glue layer")

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
index 9d89bdbf029f..82de68b1a452 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c
@@ -337,11 +337,11 @@ static int ipq806x_gmac_probe(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);
 	}
 
 	plat_dat->has_gmac = true;

Re: [PATCH v2] stmmac: avoid ipq806x constant overflow warning

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 12 Nov 2015 22:03:40 +0100

> @@ -337,11 +337,11 @@ static int ipq806x_gmac_probe(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);
>  	}
>  

Indeed, this looks so much better.

Applied.

Thanks for looking more deeply into this!

[PATCH v2] stmmac: avoid ipq806x constant overflow warning

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 12 Nov 2015 22:03:40 +0100

> @@ -337,11 +337,11 @@ static int ipq806x_gmac_probe(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);
>  	}
>  

Indeed, this looks so much better.

Applied.

Thanks for looking more deeply into this!

Re: [PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Geert Uytterhoeven]

On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> 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.

FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing subtle
warnings in other places, e.g. when inverting them to create bit mask, cfr.
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Geert Uytterhoeven]

On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> 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.

FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing subtle
warnings in other places, e.g. when inverting them to create bit mask, cfr.
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

[PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Geert Uytterhoeven]

On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> 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.

FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing subtle
warnings in other places, e.g. when inverting them to create bit mask, cfr.
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Joe Perches]

On Fri, 2015-11-13 at 08:37 +0100, Geert Uytterhoeven wrote:
> On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de>
> wrote:
> > 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.
> 
> FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing
> subtle
> warnings in other places, e.g. when inverting them to create bit
> mask, cfr.
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commi
> t/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6
> 
> Gr{oetje,eeting}s,

I still think specific length BIT macros
can be useful.

https://lkml.org/lkml/2015/10/16/852

Re: [PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Joe Perches]

On Fri, 2015-11-13 at 08:37 +0100, Geert Uytterhoeven wrote:
> On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de>
> wrote:
> > 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.
> 
> FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing
> subtle
> warnings in other places, e.g. when inverting them to create bit
> mask, cfr.
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commi
> t/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6
> 
> Gr{oetje,eeting}s,

I still think specific length BIT macros
can be useful.

https://lkml.org/lkml/2015/10/16/852

[PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Joe Perches]

On Fri, 2015-11-13 at 08:37 +0100, Geert Uytterhoeven wrote:
> On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de>
> wrote:
> > 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.
> 
> FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing
> subtle
> warnings in other places, e.g. when inverting them to create bit
> mask, cfr.
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commi
> t/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6
> 
> Gr{oetje,eeting}s,

I still think specific length BIT macros
can be useful.

https://lkml.org/lkml/2015/10/16/852

Re: [PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Geert Uytterhoeven]

Hi Joe,

On Fri, Nov 13, 2015 at 8:52 AM, Joe Perches <joe@perches.com> wrote:
> On Fri, 2015-11-13 at 08:37 +0100, Geert Uytterhoeven wrote:
>> On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de>
>> wrote:
>> > 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.
>>
>> FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing
>> subtle
>> warnings in other places, e.g. when inverting them to create bit
>> mask, cfr.
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commi
>> t/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6
>
> I still think specific length BIT macros
> can be useful.
>
> https://lkml.org/lkml/2015/10/16/852

Yeah!

I only recently started liking the BIT() macro (before I preferred hex, too).
Perhaps because Renesas datasheets use bit numbers all over the place ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Geert Uytterhoeven]

Hi Joe,

On Fri, Nov 13, 2015 at 8:52 AM, Joe Perches <joe@perches.com> wrote:
> On Fri, 2015-11-13 at 08:37 +0100, Geert Uytterhoeven wrote:
>> On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de>
>> wrote:
>> > 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.
>>
>> FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing
>> subtle
>> warnings in other places, e.g. when inverting them to create bit
>> mask, cfr.
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commi
>> t/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6
>
> I still think specific length BIT macros
> can be useful.
>
> https://lkml.org/lkml/2015/10/16/852

Yeah!

I only recently started liking the BIT() macro (before I preferred hex, too).
Perhaps because Renesas datasheets use bit numbers all over the place ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

[PATCH v2] stmmac: avoid ipq806x constant overflow warning

[Geert Uytterhoeven]

Hi Joe,

On Fri, Nov 13, 2015 at 8:52 AM, Joe Perches <joe@perches.com> wrote:
> On Fri, 2015-11-13 at 08:37 +0100, Geert Uytterhoeven wrote:
>> On Thu, Nov 12, 2015 at 10:03 PM, Arnd Bergmann <arnd@arndb.de>
>> wrote:
>> > 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.
>>
>> FWIW, the 64-bitness of BIT() on 64-bit platforms is also causing
>> subtle
>> warnings in other places, e.g. when inverting them to create bit
>> mask, cfr.
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commi
>> t/?id=a9efeca613a8fe5281d7c91f5c8c9ea46f2312f6
>
> I still think specific length BIT macros
> can be useful.
>
> https://lkml.org/lkml/2015/10/16/852

Yeah!

I only recently started liking the BIT() macro (before I preferred hex, too).
Perhaps because Renesas datasheets use bit numbers all over the place ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds