RE: [EXT] Re: [PATCH v6 04/15] octeontx2-af: Add mailbox support infra

-----Original Message-----
From: David Miller <davem@davemloft.net>
Sent: 06 October 2018 03:21
To: sunil.kovvuri@gmail.com
Cc: netdev@vger.kernel.org; arnd@arndb.de; linux-soc@vger.kernel.org;
sgoutham@marvell.com; amakarov@marvell.com; lbartosik@marvell.com
Subject: [EXT] Re: [PATCH v6 04/15] octeontx2-af: Add mailbox support infra


----------------------------------------------------------------------
From: sunil.kovvuri@gmail.com
Date: Thu,  4 Oct 2018 23:51:47 +0530

quoted

+int otx2_mbox_init(struct otx2_mbox *mbox, void *hwbase, struct

pci_dev *pdev,

quoted

+		   void *reg_base, int direction, int ndevs) {
+	int devid;
+	struct otx2_mbox_dev *mdev;

Please order local variable declarations from longest to shortest line.

Please audit your entire series for this problem.

Sure, will fix this and re-submit.

quoted

+int otx2_mbox_busy_poll_for_rsp(struct otx2_mbox *mbox, int devid) {
+	struct otx2_mbox_dev *mdev = &mbox->dev[devid];
+	unsigned long timeout = jiffies + 1 * HZ;
+
+	while (!time_after(jiffies, timeout)) {
+		if (mdev->num_msgs == mdev->msgs_acked)
+			return 0;
+		cpu_relax();
+	}
+	return -EIO;
+}

Probably not a good idea to poll something in the kernel for an entire
second.  Please add a preemption point like a usleep() or similar.
cpu_relax() does not yield the cpu to the scheduler.

Thank you.

APIs with both modes are added here i.e 
otx2_mbox_wait_for_rsp() - which sleeps on every check as you suggested.
                                                    This API will be used 99% of the cases.
otx2_mbox_busy_poll_for_rsp() - This API is a busy poll one which is intended to be used in
                                                             cases where polling is not allowed.  An example would be
                                                             ' .ndo_set_rx_mode' when netdev driver has to change mode
                                                             It frames and sends mailbox message to this AF driver and busy polls
                                                             for response.

Thanks,
Sunil.