[PATCH v3 3/3] platform/x86: intel_pmc_core: Instantiate pmc_core device on legacy platforms

[Rajat Jain]

Add code to instantiate the pmc_core platform device and thus attach to
the driver, if the ACPI device for the same ("INT33A1") is not present
in a system where it should be. This was discussed here:
https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg1966991.html

Signed-off-by: Rajat Jain <rajatja@xxxxxxxxxx>
---
v3: (first version of *this* patch -to go with rest of v3 patchset)
v2: (does not exist)
v1: (does not exist)

 drivers/platform/x86/Makefile                 |  2 +-
 .../platform/x86/intel_pmc_core_plat_init.c   | 64 +++++++++++++++++++
 2 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 drivers/platform/x86/intel_pmc_core_plat_init.c

diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index 86cb76677bc8..83d0bb9a14bb 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -89,7 +89,7 @@ obj-$(CONFIG_INTEL_BXTWC_PMIC_TMU)	+= intel_bxtwc_tmu.o
 obj-$(CONFIG_INTEL_TELEMETRY)	+= intel_telemetry_core.o \
 				   intel_telemetry_pltdrv.o \
 				   intel_telemetry_debugfs.o
-obj-$(CONFIG_INTEL_PMC_CORE)    += intel_pmc_core.o
+obj-$(CONFIG_INTEL_PMC_CORE)    += intel_pmc_core.o intel_pmc_core_plat_init.o
 obj-$(CONFIG_PMC_ATOM)		+= pmc_atom.o
 obj-$(CONFIG_MLX_PLATFORM)	+= mlx-platform.o
 obj-$(CONFIG_INTEL_TURBO_MAX_3) += intel_turbo_max_3.o
diff --git a/drivers/platform/x86/intel_pmc_core_plat_init.c b/drivers/platform/x86/intel_pmc_core_plat_init.c
new file mode 100644
index 000000000000..45be89e7586c
--- /dev/null
+++ b/drivers/platform/x86/intel_pmc_core_plat_init.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Intel PMC Core platform init
+ * Copyright (c) 2019, Google Inc.
+ * Author - Rajat Jain
+ *
+ * This code instantiates platform devices for intel_pmc_core driver, only
+ * on supported platforms that may not have the ACPI devices in the ACPI tables.
+ * No new platforms should be added here, because we expect that new platforms
+ * should all have the ACPI device, which is the preferred way of enumeration.
+ */
+
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+
+#include <asm/cpu_device_id.h>
+#include <asm/intel-family.h>
+
+static struct platform_device pmc_core_device = {
+	.name = "pmc_core",
+};
+
+static int dummy;
+/*
+ * INTEL_CPU_FAM6 macro won't take NULL for driver_data (uses &driver_data),
+ * thus provide a dummy driver_data.
+ */
+static const struct x86_cpu_id intel_pmc_core_ids[] = {
+	INTEL_CPU_FAM6(SKYLAKE_MOBILE, dummy),
+	INTEL_CPU_FAM6(SKYLAKE_DESKTOP, dummy),
+	INTEL_CPU_FAM6(KABYLAKE_MOBILE, dummy),
+	INTEL_CPU_FAM6(KABYLAKE_DESKTOP, dummy),
+	INTEL_CPU_FAM6(CANNONLAKE_MOBILE, dummy),
+	INTEL_CPU_FAM6(ICELAKE_MOBILE, dummy),
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, intel_pmc_core_ids);
+
+static int __init pmc_core_platform_init(void)
+{
+	int ret;
+
+	/* Skip creating the platform device if ACPI already has a device */
+	if (acpi_dev_present("INT33A1", NULL, -1) ||
+	    !x86_match_cpu(intel_pmc_core_ids))
+		return -ENODEV;
+
+	ret = platform_device_register(&pmc_core_device);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void __exit pmc_core_platform_exit(void)
+{
+	if (!acpi_dev_present("INT33A1", NULL, -1) &&
+	    x86_match_cpu(intel_pmc_core_ids))
+		platform_device_unregister(&pmc_core_device);
+}
+
+module_init(pmc_core_platform_init);
+module_exit(pmc_core_platform_exit);
-- 
2.21.0.392.gf8f6787159e-goog