On Sun, Jan 12, 2020 at 11:18 PM Samuel Holland [off-list ref] wrote:

+static int sun6i_msgbox_send_data(struct mbox_chan *chan, void *data)
+{
+       struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
+       int n = channel_number(chan);
+       uint32_t msg = *(uint32_t *)data;
+
+       /* Using a channel backwards gets the hardware into a bad state. */
+       if (WARN_ON_ONCE(!(readl(mbox->regs + CTRL_REG(n)) & CTRL_TX(n))))
+               return 0;
+
+       /* We cannot post a new message if the FIFO is full. */
+       if (readl(mbox->regs + FIFO_STAT_REG(n)) & FIFO_STAT_MASK) {
+               mbox_dbg(mbox, "Channel %d busy sending 0x%08x\n", n, msg);
+               return -EBUSY;
+       }
+

This check should go into sun6i_msgbox_last_tx_done().
send_data() assumes all is clear to send next packet.

.....

+
+       mbox->controller.dev           = dev;
+       mbox->controller.ops           = &sun6i_msgbox_chan_ops;
+       mbox->controller.chans         = chans;
+       mbox->controller.num_chans     = NUM_CHANS;
+       mbox->controller.txdone_irq    = false;
+       mbox->controller.txdone_poll   = true;
+       mbox->controller.txpoll_period = 5;
+

nit:  just a single space should do too.

Sorry, for some reason I thought I had replied to this patch, but
apparently not. My mistake. Do you want to revise this submission or
send another patch on top?

thanks

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