[PATCH v2 0/2] dtc: Improve checks for i2c reg properties

[PATCH v2 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.

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 v2 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-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org>
Reported-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
Signed-off-by: Joel Stanley <joel-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org>
---
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 v2 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-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org>
---
 checks.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/checks.c b/checks.c
index feb1721f2603..2d98a468f878 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 > 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 v2 2/2] checks: Improve i2c reg property checking

[Stephen Rothwell]

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Hi Joel,

On Thu, 28 May 2020 16:50:37 +0930 Joel Stanley <joel@jms.id.au> wrote:
>
>  
>  #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 > 0x3ff)

Shouldn't this be

		if ((reg & I2C_TEN_BIT_ADDRESS) && ((reg & ~I2C_TEN_BIT_ADDRESS) > 0x3ff))

-- 
Cheers,
Stephen Rothwell

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Re: [PATCH v2 2/2] checks: Improve i2c reg property checking

[Joel Stanley]

On Thu, 28 May 2020 at 08:31, Stephen Rothwell <sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org> wrote:
>
> Hi Joel,
>
> On Thu, 28 May 2020 16:50:37 +0930 Joel Stanley <joel-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org> wrote:
> >
> >
> >  #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 > 0x3ff)
>
> Shouldn't this be
>
>                 if ((reg & I2C_TEN_BIT_ADDRESS) && ((reg & ~I2C_TEN_BIT_ADDRESS) > 0x3ff))

Yes, good catch.

There are no device trees that set the I2C_TEN_BIT_ADDRESS flag in the
kernel, so it is untested.