[PATCH v3 0/2] dtc: Improve checks for i2c reg properties

[PATCH v3 0/2] dtc: Improve checks for i2c reg properties

[Joel Stanley]

This is to fix a build warning in the Linux kernel caused by dtc
incorrectly warning about I2C_OWN_SLAVE_ADDRESS.

v3 fixes the 10 bit size check
v2 contains a second patch to check for 10 bit vs 7 bit addresses.

Joel Stanley (2):
  checks: Remove warning for I2C_OWN_SLAVE_ADDRESS
  checks: Improve i2c reg property checking

 checks.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

-- 
2.26.2

[PATCH v3 1/2] checks: Remove warning for I2C_OWN_SLAVE_ADDRESS

[Joel Stanley]

dtc does a sanity check on reg properties that they are within the 10
bit address range for i2c slave addresses. In the case of multi-master
buses or devices that act as a slave, the binding may describe an
address that the bus will listen on as a device. Do not warn when this
flag is set.

See Documentation/devicetree/bindings/i2c/i2c.txt.

This fixes the following build warnings reported by Stephen and by Arnd:

arch/arm/boot/dts/aspeed-bmc-facebook-yosemitev2.dts:126.11-130.4:
  Warning (i2c_bus_reg): /ahb/apb/bus@1e78a000/i2c-bus@80/ipmb1@10:
    I2C bus unit address format error, expected "40000010"
arch/arm/boot/dts/aspeed-bmc-facebook-yosemitev2.dts:128.3-30:
  Warning (i2c_bus_reg): /ahb/apb/bus@1e78a000/i2c-bus@80/ipmb1@10:reg:
    I2C address must be less than 10-bits, got "0x40000010"

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
v2: Fix typo
---
 checks.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/checks.c b/checks.c
index a8213c0e13a8..feb1721f2603 100644
--- a/checks.c
+++ b/checks.c
@@ -1022,6 +1022,8 @@ static void check_i2c_bus_bridge(struct check *c, struct dt_info *dti, struct no
 }
 WARNING(i2c_bus_bridge, check_i2c_bus_bridge, NULL, &addr_size_cells);
 
+#define I2C_OWN_SLAVE_ADDRESS	(1 << 30)
+
 static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node *node)
 {
 	struct property *prop;
@@ -1044,6 +1046,8 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
 	}
 
 	reg = fdt32_to_cpu(*cells);
+	/* Ignore I2C_OWN_SLAVE_ADDRESS */
+	reg &= ~I2C_OWN_SLAVE_ADDRESS;
 	snprintf(unit_addr, sizeof(unit_addr), "%x", reg);
 	if (!streq(unitname, unit_addr))
 		FAIL(c, dti, node, "I2C bus unit address format error, expected \"%s\"",
@@ -1051,6 +1055,8 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
 
 	for (len = prop->val.len; len > 0; len -= 4) {
 		reg = fdt32_to_cpu(*(cells++));
+		/* Ignore I2C_OWN_SLAVE_ADDRESS */
+		reg &= ~I2C_OWN_SLAVE_ADDRESS;
 		if (reg > 0x3ff)
 			FAIL_PROP(c, dti, node, prop, "I2C address must be less than 10-bits, got \"0x%x\"",
 				  reg);
-- 
2.26.2

[PATCH v3 2/2] checks: Improve i2c reg property checking

[Joel Stanley]

The i2c bindings in the kernel tree describe support for 10 bit
addressing, which must be indicated with the I2C_TEN_BIT_ADDRESS flag.
When this is set the address can be up to 10 bits. When it is not set
the address is a maximum of 7 bits.

See Documentation/devicetree/bindings/i2c/i2c.txt.

Take into account this flag when checking the address is valid.

Signed-off-by: Joel Stanley <joel@jms.id.au>
---
v2: Mask reg when checking the 10-bit size
---
 checks.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/checks.c b/checks.c
index feb1721f2603..3fe979a63290 100644
--- a/checks.c
+++ b/checks.c
@@ -1023,6 +1023,7 @@ static void check_i2c_bus_bridge(struct check *c, struct dt_info *dti, struct no
 WARNING(i2c_bus_bridge, check_i2c_bus_bridge, NULL, &addr_size_cells);
 
 #define I2C_OWN_SLAVE_ADDRESS	(1 << 30)
+#define I2C_TEN_BIT_ADDRESS	(1 << 31)
 
 static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node *node)
 {
@@ -1057,10 +1058,13 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
 		reg = fdt32_to_cpu(*(cells++));
 		/* Ignore I2C_OWN_SLAVE_ADDRESS */
 		reg &= ~I2C_OWN_SLAVE_ADDRESS;
-		if (reg > 0x3ff)
+
+		if ((reg & I2C_TEN_BIT_ADDRESS) && ((reg & ~I2C_TEN_BIT_ADDRESS) > 0x3ff))
 			FAIL_PROP(c, dti, node, prop, "I2C address must be less than 10-bits, got \"0x%x\"",
 				  reg);
-
+		else if (reg > 0x7f)
+			FAIL_PROP(c, dti, node, prop, "I2C address must be less than 7-bits, got \"0x%x\". Set I2C_TEN_BIT_ADDRESS for 10 bit addresses or fix the property",
+				  reg);
 	}
 }
 WARNING(i2c_bus_reg, check_i2c_bus_reg, NULL, &reg_format, &i2c_bus_bridge);
-- 
2.26.2

Re: [PATCH v3 2/2] checks: Improve i2c reg property checking

[Serge Semin]

On Thu, May 28, 2020 at 06:26:50PM +0930, Joel Stanley wrote:
> The i2c bindings in the kernel tree describe support for 10 bit
> addressing, which must be indicated with the I2C_TEN_BIT_ADDRESS flag.
> When this is set the address can be up to 10 bits. When it is not set
> the address is a maximum of 7 bits.
> 
> See Documentation/devicetree/bindings/i2c/i2c.txt.
> 
> Take into account this flag when checking the address is valid.
> 
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
> v2: Mask reg when checking the 10-bit size
> ---
>  checks.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/checks.c b/checks.c
> index feb1721f2603..3fe979a63290 100644
> --- a/checks.c
> +++ b/checks.c
> @@ -1023,6 +1023,7 @@ static void check_i2c_bus_bridge(struct check *c, struct dt_info *dti, struct no
>  WARNING(i2c_bus_bridge, check_i2c_bus_bridge, NULL, &addr_size_cells);
>  
>  #define I2C_OWN_SLAVE_ADDRESS	(1 << 30)

> +#define I2C_TEN_BIT_ADDRESS	(1 << 31)

As Andy neatly pointed out here:
https://lore.kernel.org/lkml/20200527133656.GV1634618@smile.fi.intel.com/
(1 << 31) is UB.

-Sergey

>  
>  static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node *node)
>  {
> @@ -1057,10 +1058,13 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
>  		reg = fdt32_to_cpu(*(cells++));
>  		/* Ignore I2C_OWN_SLAVE_ADDRESS */
>  		reg &= ~I2C_OWN_SLAVE_ADDRESS;
> -		if (reg > 0x3ff)
> +
> +		if ((reg & I2C_TEN_BIT_ADDRESS) && ((reg & ~I2C_TEN_BIT_ADDRESS) > 0x3ff))
>  			FAIL_PROP(c, dti, node, prop, "I2C address must be less than 10-bits, got \"0x%x\"",
>  				  reg);
> -
> +		else if (reg > 0x7f)
> +			FAIL_PROP(c, dti, node, prop, "I2C address must be less than 7-bits, got \"0x%x\". Set I2C_TEN_BIT_ADDRESS for 10 bit addresses or fix the property",
> +				  reg);
>  	}
>  }
>  WARNING(i2c_bus_reg, check_i2c_bus_reg, NULL, &reg_format, &i2c_bus_bridge);
> -- 
> 2.26.2
> 

Re: [PATCH v3 2/2] checks: Improve i2c reg property checking

[Andy Shevchenko]

On Tue, Jun 2, 2020 at 11:03 AM Serge Semin
<Sergey.Semin@baikalelectronics.ru> wrote:
> On Thu, May 28, 2020 at 06:26:50PM +0930, Joel Stanley wrote:

...

> > +#define I2C_TEN_BIT_ADDRESS  (1 << 31)
>
> As Andy neatly pointed out here:
> https://lore.kernel.org/lkml/20200527133656.GV1634618@smile.fi.intel.com/
> (1 << 31) is UB.

Thanks, Serge. Yes, we have to use 1U in the definitions (for 31 is
necessary, for the rest is for the sake of consistency).

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 2/2] checks: Improve i2c reg property checking

[David Gibson]

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On Tue, Jun 02, 2020 at 11:28:05AM +0300, Andy Shevchenko wrote:
> On Tue, Jun 2, 2020 at 11:03 AM Serge Semin
> <Sergey.Semin@baikalelectronics.ru> wrote:
> > On Thu, May 28, 2020 at 06:26:50PM +0930, Joel Stanley wrote:
> 
> ...
> 
> > > +#define I2C_TEN_BIT_ADDRESS  (1 << 31)
> >
> > As Andy neatly pointed out here:
> > https://lore.kernel.org/lkml/20200527133656.GV1634618@smile.fi.intel.com/
> > (1 << 31) is UB.
> 
> Thanks, Serge. Yes, we have to use 1U in the definitions (for 31 is
> necessary, for the rest is for the sake of consistency).

Joel, I know it seems trivial, but I'm a bit flat out right now.  Can
you please resend with the 1U fix applied.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v3 0/2] dtc: Improve checks for i2c reg properties

[Rob Herring]

On Thu, May 28, 2020 at 2:57 AM Joel Stanley <joel@jms.id.au> wrote:
>
> This is to fix a build warning in the Linux kernel caused by dtc
> incorrectly warning about I2C_OWN_SLAVE_ADDRESS.
>
> v3 fixes the 10 bit size check
> v2 contains a second patch to check for 10 bit vs 7 bit addresses.
>
> Joel Stanley (2):
>   checks: Remove warning for I2C_OWN_SLAVE_ADDRESS
>   checks: Improve i2c reg property checking

Reviewed-by: Rob Herring <robh@kernel.org>

I'll sync the kernel copy when David applies.

Rob