详解ARM的AMBA设备中的DMA设备PL08X的Linux驱动

第 2 章 ARM的PL08X的代码的详细解析 第二部分

/*
 * Initialise the DMAC channels.
 * Make a local wrapper to hold required data
 */
static int pl08x_dma_enumerate_channels(void)
{
	int dma_chan;
	struct pl08x_dma_chan *local_chan;

	dma_cap_set(DMA_MEMCPY, dmac.cap_mask);
	dma_cap_set(DMA_SLAVE, dmac.cap_mask);
	if (dmac.chancnt)
		dev_err(&pd.dmac->dev, "%s - chancnt already set\n", __func__);
	INIT_LIST_HEAD(&dmac.channels);

	for (dma_chan = 0; dma_chan < MAX_DMA_CHANNELS; dma_chan++) {

		local_chan = kzalloc(sizeof(struct pl08x_dma_chan),
					GFP_KERNEL);
		if (!local_chan) {
			dev_err(&pd.dmac->dev,
				"%s - no memory for channel\n", __func__);
			return dmac.chancnt;
		}

		/*
		 * Save the DMAC channel number
		 * to indicate which registers to access
		 */
		local_chan->chan_id = dma_chan;
		local_chan->chan.device = &dmac;
		atomic_set(&local_chan->last_issued, 0);
		local_chan->lc = atomic_read(&local_chan->last_issued);
		if (pd.pd->reserved_for_slave)
			local_chan->slave_only = pd.pd->reserved_for_slave(dma_chan);
		else
			dev_err(&pd.dmac->dev,
				"%s - can't establish channels reserved for slaves\n",
					__func__);

		spin_lock_init(&local_chan->lock);
		INIT_LIST_HEAD(&local_chan->desc_list);
		INIT_LIST_HEAD(&local_chan->release_list);

		list_add_tail(&local_chan->chan.device_node, &dmac.channels);

		pd.chanwrap[dmac.chancnt++] = local_chan;
	}

	return dmac.chancnt;
}