On 18 November 2014 at 04:11, Andrew Bresticker [off-list ref] wrote:

+
+static int tegra_xusb_mbox_send_data(struct mbox_chan *chan, void *data)
+{
+       struct tegra_xusb_mbox *mbox = to_tegra_mbox(chan->mbox);
+       struct tegra_xusb_mbox_msg *msg = data;
+       unsigned long flags;
+       u32 reg, owner;
+
+       dev_dbg(mbox->mbox.dev, "TX message %#x:%#x\n", msg->cmd, msg->data);
+
+       /* ACK/NAK must be sent with the controller as the mailbox owner */
+       if (msg->cmd == MBOX_CMD_ACK || msg->cmd == MBOX_CMD_NAK)
+               owner = MBOX_OWNER_FW;
+       else
+               owner = MBOX_OWNER_SW;
+
+       spin_lock_irqsave(&mbox->lock, flags);
+
+       /* Acquire mailbox */
+       if (mbox_readl(mbox, XUSB_CFG_ARU_MBOX_OWNER) != MBOX_OWNER_NONE) {
+               dev_err(mbox->mbox.dev, "Mailbox not idle\n");
+               goto busy;
+       }
+       mbox_writel(mbox, owner, XUSB_CFG_ARU_MBOX_OWNER);
+       if (mbox_readl(mbox, XUSB_CFG_ARU_MBOX_OWNER) != owner) {
+               dev_err(mbox->mbox.dev, "Failed to acquire mailbox");
+               goto busy;
+       }
+
+       mbox_writel(mbox, mbox_pack_msg(msg), XUSB_CFG_ARU_MBOX_DATA_IN);
+       reg = mbox_readl(mbox, XUSB_CFG_ARU_MBOX_CMD);
+       reg |= MBOX_INT_EN | MBOX_DEST_FALC;
+       mbox_writel(mbox, reg, XUSB_CFG_ARU_MBOX_CMD);
+
+       spin_unlock_irqrestore(&mbox->lock, flags);
+
+       return 0;
+busy:
+       spin_unlock_irqrestore(&mbox->lock, flags);
+       return -EBUSY;
+}
+
+static int tegra_xusb_mbox_startup(struct mbox_chan *chan)
+{
+       return 0;
+}
+
+static void tegra_xusb_mbox_shutdown(struct mbox_chan *chan)
+{
+}
+
+static bool tegra_xusb_mbox_last_tx_done(struct mbox_chan *chan)
+{
+       /*
+        * Transmissions are assumed to be completed as soon as they are
+        * written to the mailbox.
+        */
+       return true;

In .send_data() you you mark the channel busy by setting the
XUSB_CFG_ARU_MBOX_OWNER to !MBOX_OWNER_NONE, which remains so until
you get an IRQ. So maybe you should check for the OWNER_NONE flag in
.last_tx_done()?

-Jassi
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