+static int peci_locked_xfer(struct peci_adapter *adapter,
+			    struct peci_xfer_msg *msg,
+			    bool do_retry,
+			    bool has_aw_fcs)
+{
+	ktime_t start, end;
+	s64 elapsed_ms;
+	int rc = 0;
+
+	if (!adapter->xfer) {
+		dev_dbg(&adapter->dev, "PECI level transfers not supported\n");
+		return -ENODEV;
+	}
+
+	if (in_atomic() || irqs_disabled()) {

Hi Jae

Is there a real need to do transfers in atomic context, or with
interrupts disabled? 

+		rt_mutex_trylock(&adapter->bus_lock);
+		if (!rc)
+			return -EAGAIN; /* PECI activity is ongoing */
+	} else {
+		rt_mutex_lock(&adapter->bus_lock);
+	}
+
+	if (do_retry)
+		start = ktime_get();
+
+	do {
+		rc = adapter->xfer(adapter, msg);
+
+		if (!do_retry)
+			break;
+
+		/* Per the PECI spec, need to retry commands that return 0x8x */
+		if (!(!rc && ((msg->rx_buf[0] & DEV_PECI_CC_RETRY_ERR_MASK) ==
+			      DEV_PECI_CC_TIMEOUT)))
+			break;
+
+		/* Set the retry bit to indicate a retry attempt */
+		msg->tx_buf[1] |= DEV_PECI_RETRY_BIT;
+
+		/* Recalculate the AW FCS if it has one */
+		if (has_aw_fcs)
+			msg->tx_buf[msg->tx_len - 1] = 0x80 ^
+						peci_aw_fcs((u8 *)msg,
+							    2 + msg->tx_len);
+
+		/* Retry for at least 250ms before returning an error */
+		end = ktime_get();
+		elapsed_ms = ktime_to_ms(ktime_sub(end, start));
+		if (elapsed_ms >= DEV_PECI_RETRY_TIME_MS) {
+			dev_dbg(&adapter->dev, "Timeout retrying xfer!\n");
+			break;
+		}
+	} while (true);

So you busy loop to 1/4 second? How about putting a sleep in here so
other things can be done between each retry.

And should it not return -ETIMEDOUT after that 1/4 second?

+static int peci_scan_cmd_mask(struct peci_adapter *adapter)
+{
+	struct peci_xfer_msg msg;
+	u32 dib;
+	int rc = 0;
+
+	/* Update command mask just once */
+	if (adapter->cmd_mask & BIT(PECI_CMD_PING))
+		return 0;
+
+	msg.addr      = PECI_BASE_ADDR;
+	msg.tx_len    = GET_DIB_WR_LEN;
+	msg.rx_len    = GET_DIB_RD_LEN;
+	msg.tx_buf[0] = GET_DIB_PECI_CMD;
+
+	rc = peci_xfer(adapter, &msg);
+	if (rc < 0) {
+		dev_dbg(&adapter->dev, "PECI xfer error, rc : %d\n", rc);
+		return rc;
+	}
+
+	dib = msg.rx_buf[0] | (msg.rx_buf[1] << 8) |
+	      (msg.rx_buf[2] << 16) | (msg.rx_buf[3] << 24);
+
+	/* Check special case for Get DIB command */
+	if (dib == 0x00) {
+		dev_dbg(&adapter->dev, "DIB read as 0x00\n");
+		return -1;
+	}
+
+	if (!rc) {
+		/**
+		 * setting up the supporting commands based on minor rev#
+		 * see PECI Spec Table 3-1
+		 */
+		dib = (dib >> 8) & 0xF;
+
+		if (dib >= 0x1) {
+			adapter->cmd_mask |= BIT(PECI_CMD_RD_PKG_CFG);
+			adapter->cmd_mask |= BIT(PECI_CMD_WR_PKG_CFG);
+		}
+
+		if (dib >= 0x2)
+			adapter->cmd_mask |= BIT(PECI_CMD_RD_IA_MSR);
+
+		if (dib >= 0x3) {
+			adapter->cmd_mask |= BIT(PECI_CMD_RD_PCI_CFG_LOCAL);
+			adapter->cmd_mask |= BIT(PECI_CMD_WR_PCI_CFG_LOCAL);
+		}
+
+		if (dib >= 0x4)
+			adapter->cmd_mask |= BIT(PECI_CMD_RD_PCI_CFG);
+
+		if (dib >= 0x5)
+			adapter->cmd_mask |= BIT(PECI_CMD_WR_PCI_CFG);
+
+		if (dib >= 0x6)
+			adapter->cmd_mask |= BIT(PECI_CMD_WR_IA_MSR);

Lots of magic numbers here. Can they be replaced with #defines.  Also,
it looks like a switch statement could be used, with fall through.

+
+		adapter->cmd_mask |= BIT(PECI_CMD_GET_TEMP);
+		adapter->cmd_mask |= BIT(PECI_CMD_GET_DIB);
+		adapter->cmd_mask |= BIT(PECI_CMD_PING);
+	} else {
+		dev_dbg(&adapter->dev, "Error reading DIB, rc : %d\n", rc);
+	}
+
+	return rc;
+}
+

+static int peci_ioctl_get_temp(struct peci_adapter *adapter, void *vmsg)
+{
+	struct peci_get_temp_msg *umsg = vmsg;
+	struct peci_xfer_msg msg;
+	int rc;
+

Is this getting the temperature?

+	rc = peci_cmd_support(adapter, PECI_CMD_GET_TEMP);
+	if (rc < 0)
+		return rc;
+
+	msg.addr      = umsg->addr;
+	msg.tx_len    = GET_TEMP_WR_LEN;
+	msg.rx_len    = GET_TEMP_RD_LEN;
+	msg.tx_buf[0] = GET_TEMP_PECI_CMD;
+
+	rc = peci_xfer(adapter, &msg);
+	if (rc < 0)
+		return rc;
+
+	umsg->temp_raw = msg.rx_buf[0] | (msg.rx_buf[1] << 8);
+
+	return 0;
+}

+static long peci_ioctl(struct file *file, unsigned int iocmd, unsigned long arg)
+{
+	struct peci_adapter *adapter = file->private_data;
+	void __user *argp = (void __user *)arg;
+	unsigned int msg_len;
+	enum peci_cmd cmd;
+	u8 *msg;
+	int rc = 0;
+
+	dev_dbg(&adapter->dev, "ioctl, cmd=0x%x, arg=0x%lx\n", iocmd, arg);
+
+	switch (iocmd) {
+	case PECI_IOC_PING:
+	case PECI_IOC_GET_DIB:
+	case PECI_IOC_GET_TEMP:
+	case PECI_IOC_RD_PKG_CFG:
+	case PECI_IOC_WR_PKG_CFG:
+	case PECI_IOC_RD_IA_MSR:
+	case PECI_IOC_RD_PCI_CFG:
+	case PECI_IOC_RD_PCI_CFG_LOCAL:
+	case PECI_IOC_WR_PCI_CFG_LOCAL:
+		cmd = _IOC_TYPE(iocmd) - PECI_IOC_BASE;
+		msg_len = _IOC_SIZE(iocmd);
+		break;

Adding new ioctl calls is pretty frowned up. Can you export this info
via /sysfs?

Also, should there be some permission checks here? Or is any user
allowed to call these ioctls?

	Andrew