tpm/tpm_crb: implement tpm crb idle state

The register TPM_CRB_CTRL_REQ_x contains bits goIdle and cmdReady for
SW to indicate that the device can enter or should exit the idle state.

The legacy ACPI-start (SMI + DMA) based devices do not support these
bits and the idle state management is not exposed to the host SW.
Thus, this functionality only is enabled only for a CRB start (MMIO)
based devices.

Based on Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
original patch:
'tpm_crb: implement power tpm crb power management'

To keep the implementation local to the hw we don't use wait_for_tpm_stat
for polling the TPM_CRB_CTRL_REQ.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/tpm_crb.c

@@ -83,6 +83,75 @@ struct crb_priv {
 	u32 cmd_size;
 };
 
+/**
+ * crb_go_idle - request tpm crb device to go the idle state
+ *
+ * @dev:  crb device
+ * @priv: crb private data
+ *
+ * Write CRB_CTRL_REQ_GO_IDLE to TPM_CRB_CTRL_REQ
+ * The device should respond within TIMEOUT_C by clearing the bit.
+ * Anyhow, we do not wait here as a consequent CMD_READY request
+ * will be handled correctly even if idle was not completed.
+ *
+ * The function does nothing for devices with ACPI-start method.
+ *
+ * Return: 0 always
+ */
+static int __maybe_unused crb_go_idle(struct device *dev, struct crb_priv *priv)
+{
+	if (priv->flags & CRB_FL_ACPI_START)
+		return 0;
+
+	iowrite32(CRB_CTRL_REQ_GO_IDLE, &priv->cca->req);
+	/* we don't really care when this settles */
+
+	return 0;
+}
+
+/**
+ * crb_cmd_ready - request tpm crb device to enter ready state
+ *
+ * @dev:  crb device
+ * @priv: crb private data
+ *
+ * Write CRB_CTRL_REQ_CMD_READY to TPM_CRB_CTRL_REQ
+ * and poll till the device acknowledge it by clearing the bit.
+ * The device should respond within TIMEOUT_C.
+ *
+ * The function does nothing for devices with ACPI-start method
+ *
+ * Return: 0 on success -ETIME on timeout;
+ */
+static int __maybe_unused crb_cmd_ready(struct device *dev,
+					struct crb_priv *priv)
+{
+	ktime_t stop, start;
+
+	if (priv->flags & CRB_FL_ACPI_START)
+		return 0;
+
+	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->cca->req);
+
+	start = ktime_get();
+	stop = ktime_add(start, ms_to_ktime(TPM2_TIMEOUT_C));
+	do {
+		if (!(ioread32(&priv->cca->req) & CRB_CTRL_REQ_CMD_READY)) {
+			dev_dbg(dev, "cmdReady in %lld usecs\n",
+				ktime_to_us(ktime_sub(ktime_get(), start)));
+			return 0;
+		}
+		usleep_range(50, 100);
+	} while (ktime_before(ktime_get(), stop));
+
+	if (ioread32(&priv->cca->req) & CRB_CTRL_REQ_CMD_READY) {
+		dev_warn(dev, "cmdReady timed out\n");
+		return -ETIME;
+	}
+
+	return 0;
+}
+
 static SIMPLE_DEV_PM_OPS(crb_pm, tpm_pm_suspend, tpm_pm_resume);
 
 static u8 crb_status(struct tpm_chip *chip)