static void pl011_dma_probe()

in serial/amba-pl011.c [369:499]

• 102 lines of code
• 22 McCabe index (conditional complexity)

static void pl011_dma_probe(struct uart_amba_port *uap)
{
	/* DMA is the sole user of the platform data right now */
	struct amba_pl011_data *plat = dev_get_platdata(uap->port.dev);
	struct device *dev = uap->port.dev;
	struct dma_slave_config tx_conf = {
		.dst_addr = uap->port.mapbase +
				 pl011_reg_to_offset(uap, REG_DR),
		.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
		.direction = DMA_MEM_TO_DEV,
		.dst_maxburst = uap->fifosize >> 1,
		.device_fc = false,
	};
	struct dma_chan *chan;
	dma_cap_mask_t mask;

	uap->dma_probed = true;
	chan = dma_request_chan(dev, "tx");
	if (IS_ERR(chan)) {
		if (PTR_ERR(chan) == -EPROBE_DEFER) {
			uap->dma_probed = false;
			return;
		}

		/* We need platform data */
		if (!plat || !plat->dma_filter) {
			dev_info(uap->port.dev, "no DMA platform data\n");
			return;
		}

		/* Try to acquire a generic DMA engine slave TX channel */
		dma_cap_zero(mask);
		dma_cap_set(DMA_SLAVE, mask);

		chan = dma_request_channel(mask, plat->dma_filter,
						plat->dma_tx_param);
		if (!chan) {
			dev_err(uap->port.dev, "no TX DMA channel!\n");
			return;
		}
	}

	dmaengine_slave_config(chan, &tx_conf);
	uap->dmatx.chan = chan;

	dev_info(uap->port.dev, "DMA channel TX %s\n",
		 dma_chan_name(uap->dmatx.chan));

	/* Optionally make use of an RX channel as well */
	chan = dma_request_slave_channel(dev, "rx");

	if (!chan && plat && plat->dma_rx_param) {
		chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);

		if (!chan) {
			dev_err(uap->port.dev, "no RX DMA channel!\n");
			return;
		}
	}

	if (chan) {
		struct dma_slave_config rx_conf = {
			.src_addr = uap->port.mapbase +
				pl011_reg_to_offset(uap, REG_DR),
			.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
			.direction = DMA_DEV_TO_MEM,
			.src_maxburst = uap->fifosize >> 2,
			.device_fc = false,
		};
		struct dma_slave_caps caps;

		/*
		 * Some DMA controllers provide information on their capabilities.
		 * If the controller does, check for suitable residue processing
		 * otherwise assime all is well.
		 */
		if (0 == dma_get_slave_caps(chan, &caps)) {
			if (caps.residue_granularity ==
					DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
				dma_release_channel(chan);
				dev_info(uap->port.dev,
					"RX DMA disabled - no residue processing\n");
				return;
			}
		}
		dmaengine_slave_config(chan, &rx_conf);
		uap->dmarx.chan = chan;

		uap->dmarx.auto_poll_rate = false;
		if (plat && plat->dma_rx_poll_enable) {
			/* Set poll rate if specified. */
			if (plat->dma_rx_poll_rate) {
				uap->dmarx.auto_poll_rate = false;
				uap->dmarx.poll_rate = plat->dma_rx_poll_rate;
			} else {
				/*
				 * 100 ms defaults to poll rate if not
				 * specified. This will be adjusted with
				 * the baud rate at set_termios.
				 */
				uap->dmarx.auto_poll_rate = true;
				uap->dmarx.poll_rate =  100;
			}
			/* 3 secs defaults poll_timeout if not specified. */
			if (plat->dma_rx_poll_timeout)
				uap->dmarx.poll_timeout =
					plat->dma_rx_poll_timeout;
			else
				uap->dmarx.poll_timeout = 3000;
		} else if (!plat && dev->of_node) {
			uap->dmarx.auto_poll_rate = of_property_read_bool(
						dev->of_node, "auto-poll");
			if (uap->dmarx.auto_poll_rate) {
				u32 x;

				if (0 == of_property_read_u32(dev->of_node,
						"poll-rate-ms", &x))
					uap->dmarx.poll_rate = x;
				else
					uap->dmarx.poll_rate = 100;
				if (0 == of_property_read_u32(dev->of_node,
						"poll-timeout-ms", &x))
					uap->dmarx.poll_timeout = x;
				else
					uap->dmarx.poll_timeout = 3000;
			}
		}
		dev_info(uap->port.dev, "DMA channel RX %s\n",
			 dma_chan_name(uap->dmarx.chan));
	}
}