tpm: Autodetect itpm devices

Some Lenovos have TPMs that require a quirk to function correctly. This can
be autodetected by checking whether the device has a _HID of INTC0102. This
is an invalid PNPid, and as such is discarded by the pnp layer - however
it's still present in the ACPI code, so we can pull it out that way. This
means that the quirk won't be automatically applied on non-ACPI systems,
but without ACPI we don't have any way to identify the chip anyway so I
don't think that's a great concern.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Tested-by: Andy Isaacson <adi@hexapodia.org>
Signed-off-by: James Morris <jmorris@namei.org>

drivers/char/tpm/tpm_tis.c

@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/interrupt.h>
 #include <linux/wait.h>
+#include <linux/acpi.h>
 #include "tpm.h"
 
 #define TPM_HEADER_SIZE 10
@@ -78,6 +79,26 @@ enum tis_defaults {
 static LIST_HEAD(tis_chips);
 static DEFINE_SPINLOCK(tis_lock);
 
+#ifdef CONFIG_ACPI
+static int is_itpm(struct pnp_dev *dev)
+{
+	struct acpi_device *acpi = pnp_acpi_device(dev);
+	struct acpi_hardware_id *id;
+
+	list_for_each_entry(id, &acpi->pnp.ids, list) {
+		if (!strcmp("INTC0102", id->id))
+			return 1;
+	}
+
+	return 0;
+}
+#else
+static int is_itpm(struct pnp_dev *dev)
+{
+	return 0;
+}
+#endif
+
 static int check_locality(struct tpm_chip *chip, int l)
 {
 	if ((ioread8(chip->vendor.iobase + TPM_ACCESS(l)) &
@@ -472,6 +493,9 @@ static int tpm_tis_init(struct device *dev, resource_size_t start,
 		 "1.2 TPM (device-id 0x%X, rev-id %d)\n",
 		 vendor >> 16, ioread8(chip->vendor.iobase + TPM_RID(0)));
 
+	if (is_itpm(to_pnp_dev(dev)))
+		itpm = 1;
+
 	if (itpm)
 		dev_info(dev, "Intel iTPM workaround enabled\n");