vfio: platform: add support for ACPI probe

The code is using the compatible DT string to associate a reset driver
with the actual device itself. The compatible string does not exist on
ACPI based systems. HID is the unique identifier for a device driver
instead.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

2 files changed, 60 insertions, 5 deletions

diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
index 307d61d2aea2..716f421d1b01 100644
--- a/drivers/vfio/platform/vfio_platform_common.c
+++ b/drivers/vfio/platform/vfio_platform_common.c
@@ -13,6 +13,7 @@
  */
 
 #include <linux/device.h>
+#include <linux/acpi.h>
 #include <linux/iommu.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -49,6 +50,27 @@ static vfio_platform_reset_fn_t vfio_platform_lookup_reset(const char *compat,
         return reset_fn;
 }
 
+static int vfio_platform_acpi_probe(struct vfio_platform_device *vdev,
+                                    struct device *dev)
+{
+        struct acpi_device *adev;
+
+        if (acpi_disabled)
+                return -ENOENT;
+
+        adev = ACPI_COMPANION(dev);
+        if (!adev) {
+                pr_err("VFIO: ACPI companion device not found for %s\n",
+                        vdev->name);
+                return -ENODEV;
+        }
+
+#ifdef CONFIG_ACPI
+        vdev->acpihid = acpi_device_hid(adev);
+#endif
+        return WARN_ON(!vdev->acpihid) ? -EINVAL : 0;
+}
+
 static bool vfio_platform_has_reset(struct vfio_platform_device *vdev)
 {
         return vdev->of_reset ? true : false;
@@ -547,6 +569,37 @@ static const struct vfio_device_ops vfio_platform_ops = {
         .mmap           = vfio_platform_mmap,
 };
 
+int vfio_platform_of_probe(struct vfio_platform_device *vdev,
+                           struct device *dev)
+{
+        int ret;
+
+        ret = device_property_read_string(dev, "compatible",
+                                          &vdev->compat);
+        if (ret)
+                pr_err("VFIO: cannot retrieve compat for %s\n",
+                        vdev->name);
+
+        return ret;
+}
+
+/*
+ * There can be two kernel build combinations. One build where
+ * ACPI is not selected in Kconfig and another one with the ACPI Kconfig.
+ *
+ * In the first case, vfio_platform_acpi_probe will return since
+ * acpi_disabled is 1. DT user will not see any kind of messages from
+ * ACPI.
+ *
+ * In the second case, both DT and ACPI is compiled in but the system is
+ * booting with any of these combinations.
+ *
+ * If the firmware is DT type, then acpi_disabled is 1. The ACPI probe routine
+ * terminates immediately without any messages.
+ *
+ * If the firmware is ACPI type, then acpi_disabled is 0. All other checks are
+ * valid checks. We cannot claim that this system is DT.
+ */
 int vfio_platform_probe_common(struct vfio_platform_device *vdev,
                                struct device *dev)
 {
@@ -556,11 +609,12 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
         if (!vdev)
                 return -EINVAL;
 
-        ret = device_property_read_string(dev, "compatible", &vdev->compat);
-        if (ret) {
-                pr_err("VFIO: cannot retrieve compat for %s\n", vdev->name);
-                return -EINVAL;
-        }
+        ret = vfio_platform_acpi_probe(vdev, dev);
+        if (ret)
+                ret = vfio_platform_of_probe(vdev, dev);
+
+        if (ret)
+                return ret;
 
         vdev->device = dev;
 
diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
index 71ed7d1c1b7d..ba9e4f8b0746 100644
--- a/drivers/vfio/platform/vfio_platform_private.h
+++ b/drivers/vfio/platform/vfio_platform_private.h
@@ -58,6 +58,7 @@ struct vfio_platform_device {
         struct mutex                    igate;
         struct module                   *parent_module;
         const char                      *compat;
+        const char                      *acpihid;
         struct module                   *reset_module;
         struct device                   *device;