post/i2c: Add ability to ignore I2C devices

Add the ability to not report an I2C POST error for a set of given I2C
addresses on bootup.  This is useful for cases when a device may or may
not be present, and neither case is considered an error.  For example:

- Some form factors such as XMC and Compact PCI Express have an I2C
  EEPROM whose address changes based on geographical address.  Eg
  installed in one slot its EEPROM address is, 0x50, in another its
  0x51, etc.  This allows multiple devices to have their EEPROMs present
  on the same I2C bus.  Thus the I2C devices present for an XMC or
  CPCIe card depend on if and where other cards are installed in the
  same system.

- Some cards have optional I2C devices.  Eg one hardware build
  configuration has different I2C devices than another and software
  can't determine if the optional device should be present or not.

- Some cards have optional daughtercards with I2C devices on them.

- I2C EEPROMs address range depends on their size.  Its possible to
  support differently size EEPROMs by only probing the EEPROM's base
  address and ignoring the other addresses that are impacted by its
  size.

A new CONFIG_SYS_POST_I2C_IGNORES define has been added which specifies
a list of I2C addresses for the I2C POST to ignore.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
Acked-by: Heiko Schocher <hs@denx.de>
Acked-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

doc/README.POST

@@ -665,6 +665,14 @@ listed in CONFIG_SYS_POST_I2C_ADDRS are found, and no additional
 devices are detected.  If CONFIG_SYS_POST_I2C_ADDRS is not defined
 the test will pass if any I2C device is found.
 
+The CONFIG_SYS_POST_I2C_IGNORES define can be used to list I2C
+devices which may or may not be present when using
+CONFIG_SYS_POST_I2C_ADDRS.  The I2C POST test will pass regardless
+if the devices in CONFIG_SYS_POST_I2C_IGNORES are found or not.
+This is useful in cases when I2C devices are optional (eg on a
+daughtercard that may or may not be present) or not critical
+to board operation.
+
 2.2.2.2. Watchdog timer test
 
 To test the watchdog timer the scheme mentioned above (refer to

post/drivers/i2c.c

@@ -27,8 +27,12 @@
  * For verifying the I2C bus, a full I2C bus scanning is performed.
  *
  * #ifdef CONFIG_SYS_POST_I2C_ADDRS
- *   The test is considered as passed if all the devices and
- *   only the devices in the list are found.
+ *   The test is considered as passed if all the devices and only the devices
+ *   in the list are found.
+ *   #ifdef CONFIG_SYS_POST_I2C_IGNORES
+ *     Ignore devices listed in CONFIG_SYS_POST_I2C_IGNORES.  These devices
+ *     are optional or not vital to board functionality.
+ *   #endif
  * #else [ ! CONFIG_SYS_POST_I2C_ADDRS ]
  *   The test is considered as passed if any I2C device is found.
  * #endif
@@ -40,12 +44,28 @@
 
 #if CONFIG_POST & CONFIG_SYS_POST_I2C
 
+static int i2c_ignore_device(unsigned int chip)
+{
+#ifdef CONFIG_SYS_POST_I2C_IGNORES
+	const unsigned char i2c_ignore_list[] = CONFIG_SYS_POST_I2C_IGNORES;
+	int i;
+
+	for (i = 0; i < sizeof(i2c_ignore_list); i++)
+		if (i2c_ignore_list[i] == chip)
+			return 1;
+#endif
+
+	return 0;
+}
+
 int i2c_post_test (int flags)
 {
 	unsigned int i;
 #ifndef CONFIG_SYS_POST_I2C_ADDRS
 	/* Start at address 1, address 0 is the general call address */
 	for (i = 1; i < 128; i++)
+		if (i2c_ignore_device(i))
+			continue;
 		if (i2c_probe (i) == 0)
 			return 0;
 
@@ -58,6 +78,8 @@ int i2c_post_test (int flags)
 
 	/* Start at address 1, address 0 is the general call address */
 	for (i = 1; i < 128; i++) {
+		if (i2c_ignore_device(i))
+			continue;
 		if (i2c_probe(i) != 0)
 			continue;