soc/intel/common/feature/i2c: Add common devfn mapping

Introduce a common implementation for I2C device function to bus
number mapping that can be shared across multiple Intel SoC platforms.

The implementation uses:
- CONFIG_SOC_INTEL_I2C_DEV_MAX: Kconfig value for max I2C controllers
- SOC_I2C_DEVFN(n): SoC-specific macro for I2C devfn names

This eliminates duplicate code across platforms that follow the
standard I2C controller numbering scheme.

Change-Id: Ib242d7a839ccb26394794382098cecb658adf698
Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/91258
Reviewed-by: Guvendik, Bora <bora.guvendik@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/common/feature/i2c/Kconfig

@@ -0,0 +1,8 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+config SOC_INTEL_COMMON_FEATURE_I2C_DEVFN
+	bool
+	help
+	  Common I2C device function to bus mapping implementation.
+	  SoCs using this must define SOC_I2C_DEVFN(n) macro in their
+	  pci_devs.h and CONFIG_SOC_INTEL_I2C_DEV_MAX in their Kconfig.

src/soc/intel/common/feature/i2c/Makefile.mk

@@ -0,0 +1,4 @@
+## SPDX-License-Identifier: GPL-2.0-only
+
+all-$(CONFIG_SOC_INTEL_COMMON_FEATURE_I2C_DEVFN) += i2c_devfn.c
+smm-$(CONFIG_SOC_INTEL_COMMON_FEATURE_I2C_DEVFN) += i2c_devfn.c

src/soc/intel/common/feature/i2c/i2c_devfn.c

@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <device/device.h>
+#include <drivers/i2c/designware/dw_i2c.h>
+#include <soc/pci_devs.h>
+
+/*
+ * SoC-specific I2C device function to bus number mapping.
+ *
+ * Each SoC must define:
+ * - CONFIG_SOC_INTEL_I2C_DEV_MAX: Maximum number of I2C controllers
+ * - SOC_I2C_DEVFN(n): Macro that expands to the SoC-specific I2C device
+ *   function name (e.g., PCH_DEVFN_I2Cn or PCI_DEVFN_I2Cn)
+ */
+
+_Static_assert(CONFIG_SOC_INTEL_I2C_DEV_MAX <= 8,
+	       "CONFIG_SOC_INTEL_I2C_DEV_MAX greater than 8 is not supported.");
+
+int dw_i2c_soc_devfn_to_bus(unsigned int devfn)
+{
+	switch (devfn) {
+	case SOC_I2C_DEVFN(0):
+		return 0;
+	case SOC_I2C_DEVFN(1):
+		return 1;
+	case SOC_I2C_DEVFN(2):
+		return 2;
+	case SOC_I2C_DEVFN(3):
+		return 3;
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 4
+	case SOC_I2C_DEVFN(4):
+		return 4;
+#endif
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 5
+	case SOC_I2C_DEVFN(5):
+		return 5;
+#endif
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 6
+	case SOC_I2C_DEVFN(6):
+		return 6;
+#endif
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 7
+	case SOC_I2C_DEVFN(7):
+		return 7;
+#endif
+	}
+	return -1;
+}
+
+int dw_i2c_soc_bus_to_devfn(unsigned int bus)
+{
+	switch (bus) {
+	case 0:
+		return SOC_I2C_DEVFN(0);
+	case 1:
+		return SOC_I2C_DEVFN(1);
+	case 2:
+		return SOC_I2C_DEVFN(2);
+	case 3:
+		return SOC_I2C_DEVFN(3);
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 4
+	case 4:
+		return SOC_I2C_DEVFN(4);
+#endif
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 5
+	case 5:
+		return SOC_I2C_DEVFN(5);
+#endif
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 6
+	case 6:
+		return SOC_I2C_DEVFN(6);
+#endif
+#if CONFIG_SOC_INTEL_I2C_DEV_MAX > 7
+	case 7:
+		return SOC_I2C_DEVFN(7);
+#endif
+	}
+	return -1;
+}