static irqreturn_t ti_msgmgr_queue_rx_interrupt()

in ti-msgmgr.c [202:277]

• 39 lines of code
• 6 McCabe index (conditional complexity)

static irqreturn_t ti_msgmgr_queue_rx_interrupt(int irq, void *p)
{
	struct mbox_chan *chan = p;
	struct device *dev = chan->mbox->dev;
	struct ti_msgmgr_inst *inst = dev_get_drvdata(dev);
	struct ti_queue_inst *qinst = chan->con_priv;
	const struct ti_msgmgr_desc *desc;
	int msg_count, num_words;
	struct ti_msgmgr_message message;
	void __iomem *data_reg;
	u32 *word_data;

	if (WARN_ON(!inst)) {
		dev_err(dev, "no platform drv data??\n");
		return -EINVAL;
	}

	/* Do I have an invalid interrupt source? */
	if (qinst->is_tx) {
		dev_err(dev, "Cannot handle rx interrupt on tx channel %s\n",
			qinst->name);
		return IRQ_NONE;
	}

	desc = inst->desc;
	if (ti_msgmgr_queue_is_error(desc, qinst)) {
		dev_err(dev, "Error on Rx channel %s\n", qinst->name);
		return IRQ_NONE;
	}

	/* Do I actually have messages to read? */
	msg_count = ti_msgmgr_queue_get_num_messages(desc, qinst);
	if (!msg_count) {
		/* Shared IRQ? */
		dev_dbg(dev, "Spurious event - 0 pending data!\n");
		return IRQ_NONE;
	}

	/*
	 * I have no idea about the protocol being used to communicate with the
	 * remote producer - 0 could be valid data, so I won't make a judgement
	 * of how many bytes I should be reading. Let the client figure this
	 * out.. I just read the full message and pass it on..
	 */
	message.len = desc->max_message_size;
	message.buf = (u8 *)qinst->rx_buff;

	/*
	 * NOTE about register access involved here:
	 * the hardware block is implemented with 32bit access operations and no
	 * support for data splitting.  We don't want the hardware to misbehave
	 * with sub 32bit access - For example: if the last register read is
	 * split into byte wise access, it can result in the queue getting
	 * stuck or indeterminate behavior. An out of order read operation may
	 * result in weird data results as well.
	 * Hence, we do not use memcpy_fromio or __ioread32_copy here, instead
	 * we depend on readl for the purpose.
	 *
	 * Also note that the final register read automatically marks the
	 * queue message as read.
	 */
	for (data_reg = qinst->queue_buff_start, word_data = qinst->rx_buff,
	     num_words = (desc->max_message_size / sizeof(u32));
	     num_words; num_words--, data_reg += sizeof(u32), word_data++)
		*word_data = readl(data_reg);

	/*
	 * Last register read automatically clears the IRQ if only 1 message
	 * is pending - so send the data up the stack..
	 * NOTE: Client is expected to be as optimal as possible, since
	 * we invoke the handler in IRQ context.
	 */
	mbox_chan_received_data(chan, (void *)&message);

	return IRQ_HANDLED;
}