[RESEND RFCv2 1/1] platform/x86: Add virtual PMC driver used for S2Idle

Grzegorz Jaszczyk
2023-02-09T15:21:48Z

Virtual PMC driver is meant for the guest VMs for the S2Idle
notification. Its purpose is to register S2Idle dev ops check handler,
which will evaluate ACPI _DSM just before the guest enters S2Idle power
state.

This allows to trap on MMIO access done as a consequence of _DSM
evaluation and therefore notify the VMM about the guest entering S2Idle
state.

Signed-off-by: Grzegorz Jaszczyk <jaz@semihalf.com>
---
Changelog v1..v2:
- Take advantage of acpi_s2idle_dev_ops's check() instead of notify()
---
drivers/platform/x86/Kconfig | 7 ++++
drivers/platform/x86/Makefile | 3 ++
drivers/platform/x86/virt_pmc.c | 73 +++++++++++++++++++++++++++++++++
3 files changed, 83 insertions(+)
create mode 100644 drivers/platform/x86/virt_pmc.c

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 5692385e2d26..b7c3f98031d7 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -1099,6 +1099,13 @@ config WINMATE_FM07_KEYS
buttons below the display. This module adds an input device
that delivers key events when these buttons are pressed.

+config VIRT_PMC
+ tristate "Virt PMC"
+ depends on ACPI && SUSPEND
+ help
+ The Virtual PMC driver is meant for the guest VMs and its main
+ purpose is to notify about guest entering s2idle state.
+
endif # X86_PLATFORM_DEVICES

config P2SB
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index 1d3d1b02541b..c4d3056cf4ea 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -129,6 +129,9 @@ obj-$(CONFIG_INTEL_SCU_WDT) += intel_scu_wdt.o
obj-$(CONFIG_INTEL_SCU_IPC_UTIL) += intel_scu_ipcutil.o
obj-$(CONFIG_X86_INTEL_LPSS) += pmc_atom.o

+# Virtual PMC
+obj-$(CONFIG_VIRT_PMC) += virt_pmc.o
+
# Siemens Simatic Industrial PCs
obj-$(CONFIG_SIEMENS_SIMATIC_IPC) += simatic-ipc.o

diff --git a/drivers/platform/x86/virt_pmc.c b/drivers/platform/x86/virt_pmc.c
new file mode 100644
index 000000000000..daf9c9ed86e5
--- /dev/null
+++ b/drivers/platform/x86/virt_pmc.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Virtual Power Management Controller Driver
+ *
+ * Author: Grzegorz Jaszczyk <jaz@semihalf.com>
+ */
+
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+
+#define ACPI_VIRT_PMC_DSM_UUID "9ea49ba3-434a-49a6-be30-37cc55c4d397"
+#define ACPI_VIRT_PMC_NOTIFY 1
+
+static acpi_handle virt_pmc_handle;
+
+static void virt_pmc_s2idle_notify(void)
+{
+ union acpi_object *out_obj;
+ static guid_t dsm_guid;
+
+ guid_parse(ACPI_VIRT_PMC_DSM_UUID, &dsm_guid);
+
+ out_obj = acpi_evaluate_dsm(virt_pmc_handle, &dsm_guid,
+ 0, ACPI_VIRT_PMC_NOTIFY, NULL);
+
+ acpi_handle_debug(virt_pmc_handle, "_DSM function %u evaluation %s\n",
+ ACPI_VIRT_PMC_NOTIFY, out_obj ? "successful" : "failed");
+
+ ACPI_FREE(out_obj);
+}
+
+static struct acpi_s2idle_dev_ops amd_pmc_s2idle_dev_ops = {
+ .check = virt_pmc_s2idle_notify,
+};
+
+static int virt_pmc_probe(struct platform_device *pdev)
+{
+ int err = 0;
+
+ virt_pmc_handle = ACPI_HANDLE(&pdev->dev);
+
+ err = acpi_register_lps0_dev(&amd_pmc_s2idle_dev_ops);
+ if (err)
+ dev_warn(&pdev->dev, "failed to register LPS0 sleep handler\n");
+
+ return err;
+}
+
+static int virt_pmc_remove(struct platform_device *pdev)
+{
+ acpi_unregister_lps0_dev(&amd_pmc_s2idle_dev_ops);
+
+ return 0;
+}
+
+static const struct acpi_device_id virt_pmc_acpi_ids[] = {
+ {"HYPE0001", 0}, /* _HID for XXX Power Engine, _CID PNP0D80*/
+ { }
+};
+MODULE_DEVICE_TABLE(acpi, virt_pmc_acpi_ids);
+
+static struct platform_driver virt_pmc_driver = {
+ .driver = {
+ .name = "virtual_pmc",
+ .acpi_match_table = ACPI_PTR(virt_pmc_acpi_ids),
+ },
+ .probe = virt_pmc_probe,
+ .remove = virt_pmc_remove,
+};
+
+module_platform_driver(virt_pmc_driver);
+
+MODULE_DESCRIPTION("Virtual PMC Driver");
--
2.39.1.519.gcb327c4b5f-goog