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Date:   Mon,  4 Mar 2019 15:36:57 -0600
From:   Eddie James <eajames@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-aspeed@...ts.ozlabs.org, devicetree@...r.kernel.org,
        robh+dt@...nel.org, mark.rutland@....com, joel@....id.au,
        andrew@...id.au, arnd@...db.de, gregkh@...uxfoundation.org,
        jk@...abs.org, openbmc@...ts.ozlabs.org,
        Eddie James <eajames@...ux.ibm.com>
Subject: [PATCH 3/6] drivers/misc: xdma: Add user interface

This commits adds a miscdevice to provide a user interface to the XDMA
engine. The interface provides the write operation to start DMA
operations. The DMA parameters are passed as the data to the write call.
The actual data to transfer is NOT passed through write. Note that both
directions of DMA operation are accomplished through the write command;
BMC to host and host to BMC.

The XDMA engine is restricted to only accessing the reserved memory
space on the AST2500, typically used by the VGA. For this reason, this
commit also adds a simple memory manager for this reserved memory space
which can then be allocated in pages by users calling mmap. The space
allocated by a client will be the space used in the DMA operation. For
an "upstream" (BMC to host) operation, the data in the client's area
will be transferred to the host. For a "downstream" (host to BMC)
operation, the host data will be placed in the client's memory area.

Poll is also provided in order to determine when the DMA operation is
complete for non-blocking IO.

Signed-off-by: Eddie James <eajames@...ux.ibm.com>
---
 drivers/misc/aspeed-xdma.c | 301 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 301 insertions(+)

diff --git a/drivers/misc/aspeed-xdma.c b/drivers/misc/aspeed-xdma.c
index 970ea92..16235b3 100644
--- a/drivers/misc/aspeed-xdma.c
+++ b/drivers/misc/aspeed-xdma.c
@@ -113,6 +113,12 @@ struct aspeed_xdma_cmd {
 	u32 resv1;
 };
 
+struct aspeed_xdma_vga_blk {
+	u32 phys;
+	u32 size;
+	struct list_head list;
+};
+
 struct aspeed_xdma_client;
 
 struct aspeed_xdma {
@@ -123,6 +129,8 @@ struct aspeed_xdma {
 
 	unsigned long flags;
 	unsigned int cmd_idx;
+	struct mutex list_lock;
+	struct mutex start_lock;
 	wait_queue_head_t wait;
 	struct aspeed_xdma_client *current_client;
 
@@ -131,6 +139,9 @@ struct aspeed_xdma {
 	dma_addr_t vga_dma;
 	void *cmdq;
 	void *vga_virt;
+	struct list_head vga_blks_free;
+
+	struct miscdevice misc;
 };
 
 struct aspeed_xdma_client {
@@ -298,6 +309,260 @@ static irqreturn_t aspeed_xdma_irq(int irq, void *arg)
 	return IRQ_HANDLED;
 }
 
+static u32 aspeed_xdma_alloc_vga_blk(struct aspeed_xdma *ctx, u32 req_size)
+{
+	u32 phys = 0;
+	u32 size = PAGE_ALIGN(req_size);
+	struct aspeed_xdma_vga_blk *free;
+
+	mutex_lock(&ctx->list_lock);
+
+	list_for_each_entry(free, &ctx->vga_blks_free, list) {
+		if (free->size >= size) {
+			phys = free->phys;
+
+			if (size == free->size) {
+				dev_dbg(ctx->dev,
+					"Allocd %08x[%08x r(%08x)], del.\n",
+					phys, size, req_size);
+				list_del(&free->list);
+				kfree(free);
+			} else {
+				free->phys += size;
+				free->size -= size;
+				dev_dbg(ctx->dev, "Allocd %08x[%08x r(%08x)], "
+					"shrunk %08x[%08x].\n", phys, size,
+					req_size, free->phys, free->size);
+			}
+
+			break;
+		}
+	}
+
+	mutex_unlock(&ctx->list_lock);
+
+	return phys;
+}
+
+static void aspeed_xdma_free_vga_blk(struct aspeed_xdma *ctx, u32 phys,
+				     u32 req_size)
+{
+	u32 min_free = UINT_MAX;
+	u32 size = PAGE_ALIGN(req_size);
+	const u32 end = phys + size;
+	struct aspeed_xdma_vga_blk *free;
+
+	mutex_lock(&ctx->list_lock);
+
+	list_for_each_entry(free, &ctx->vga_blks_free, list) {
+		if (end == free->phys) {
+			u32 fend = free->phys + free->size;
+
+			dev_dbg(ctx->dev,
+				"Freed %08x[%08x r(%08x)], exp %08x[%08x].\n",
+				phys, size, req_size, free->phys, free->size);
+
+			free->phys = phys;
+			free->size = fend - free->phys;
+
+			mutex_unlock(&ctx->list_lock);
+			return;
+		}
+
+		if (free->phys < min_free)
+			min_free = free->phys;
+	}
+
+	free = kzalloc(sizeof(*free), GFP_KERNEL);
+	if (free) {
+		free->phys = phys;
+		free->size = size;
+
+		dev_dbg(ctx->dev, "Freed %08x[%08x r(%08x)], new.\n", phys,
+			size, req_size);
+
+		if (phys < min_free)
+			list_add(&free->list, &ctx->vga_blks_free);
+		else
+			list_add_tail(&free->list, &ctx->vga_blks_free);
+	} else {
+		dev_err(ctx->dev, "Failed to register freed block.\n");
+	}
+
+	mutex_unlock(&ctx->list_lock);
+}
+
+static ssize_t aspeed_xdma_write(struct file *file, const char __user *buf,
+				 size_t len, loff_t *offset)
+{
+	int rc;
+	struct aspeed_xdma_op op;
+	struct aspeed_xdma_client *client = file->private_data;
+	struct aspeed_xdma *ctx = client->ctx;
+	u32 offs = client->phys ? (client->phys - ctx->vga_phys) :
+		XDMA_CMDQ_SIZE;
+
+	if (len != sizeof(struct aspeed_xdma_op))
+		return -EINVAL;
+
+	rc = copy_from_user(&op, buf, len);
+	if (rc)
+		return rc;
+
+	if (op.len > (ctx->vga_size - offs) || op.len < XDMA_BYTE_ALIGN)
+		return -EINVAL;
+
+	if (file->f_flags & O_NONBLOCK) {
+		if (!mutex_trylock(&ctx->start_lock))
+			return -EAGAIN;
+
+		if (test_bit(XDMA_IN_PRG, &ctx->flags)) {
+			mutex_unlock(&ctx->start_lock);
+			return -EAGAIN;
+		}
+	} else {
+		mutex_lock(&ctx->start_lock);
+
+		rc = wait_event_interruptible(ctx->wait,
+					      !test_bit(XDMA_IN_PRG,
+							&ctx->flags));
+		if (rc) {
+			mutex_unlock(&ctx->start_lock);
+			return -EINTR;
+		}
+	}
+
+	ctx->current_client = client;
+	set_bit(XDMA_IN_PRG, &client->flags);
+
+	aspeed_xdma_start(ctx, &op, ctx->vga_phys + offs);
+
+	mutex_unlock(&ctx->start_lock);
+
+	if (!(file->f_flags & O_NONBLOCK)) {
+		rc = wait_event_interruptible(ctx->wait,
+					      !test_bit(XDMA_IN_PRG,
+							&ctx->flags));
+		if (rc)
+			return -EINTR;
+	}
+
+	return len;
+}
+
+static __poll_t aspeed_xdma_poll(struct file *file,
+				 struct poll_table_struct *wait)
+{
+	__poll_t mask = 0;
+	__poll_t req = poll_requested_events(wait);
+	struct aspeed_xdma_client *client = file->private_data;
+	struct aspeed_xdma *ctx = client->ctx;
+
+	if (req & (EPOLLIN | EPOLLRDNORM)) {
+		if (test_bit(XDMA_IN_PRG, &client->flags))
+			poll_wait(file, &ctx->wait, wait);
+
+		if (!test_bit(XDMA_IN_PRG, &client->flags))
+			mask |= EPOLLIN | EPOLLRDNORM;
+	}
+
+	if (req & (EPOLLOUT | EPOLLWRNORM)) {
+		if (test_bit(XDMA_IN_PRG, &ctx->flags))
+			poll_wait(file, &ctx->wait, wait);
+
+		if (!test_bit(XDMA_IN_PRG, &ctx->flags))
+			mask |= EPOLLOUT | EPOLLWRNORM;
+	}
+
+	return mask;
+}
+
+static void aspeed_xdma_vma_close(struct vm_area_struct *vma)
+{
+	struct aspeed_xdma_client *client = vma->vm_private_data;
+
+	aspeed_xdma_free_vga_blk(client->ctx, client->phys, client->size);
+
+	client->phys = 0;
+	client->size = 0;
+}
+
+static const struct vm_operations_struct aspeed_xdma_vm_ops = {
+	.close =	aspeed_xdma_vma_close,
+};
+
+static int aspeed_xdma_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	int rc;
+	struct aspeed_xdma_client *client = file->private_data;
+	struct aspeed_xdma *ctx = client->ctx;
+
+	/* restrict file to one mapping */
+	if (client->size)
+		return -ENOMEM;
+
+	client->size = vma->vm_end - vma->vm_start;
+	client->phys = aspeed_xdma_alloc_vga_blk(ctx, client->size);
+	if (!client->phys) {
+		client->size = 0;
+		return -ENOMEM;
+	}
+
+	vma->vm_pgoff = (client->phys - ctx->vga_phys) >> PAGE_SHIFT;
+	vma->vm_ops = &aspeed_xdma_vm_ops;
+	vma->vm_private_data = client;
+
+	rc = dma_mmap_coherent(ctx->dev, vma, ctx->vga_virt, ctx->vga_dma,
+			       ctx->vga_size);
+	if (rc) {
+		aspeed_xdma_free_vga_blk(ctx, client->phys, client->size);
+
+		client->phys = 0;
+		client->size = 0;
+		return rc;
+	}
+
+	dev_dbg(ctx->dev, "mmap: v[%08lx] to p[%08x], s[%08x]\n",
+		vma->vm_start, client->phys, client->size);
+
+	return 0;
+}
+
+static int aspeed_xdma_open(struct inode *inode, struct file *file)
+{
+	struct miscdevice *misc = file->private_data;
+	struct aspeed_xdma *ctx = container_of(misc, struct aspeed_xdma, misc);
+	struct aspeed_xdma_client *client = kzalloc(sizeof(*client),
+						    GFP_KERNEL);
+
+	if (!client)
+		return -ENOMEM;
+
+	client->ctx = ctx;
+	file->private_data = client;
+	return 0;
+}
+
+static int aspeed_xdma_release(struct inode *inode, struct file *file)
+{
+	struct aspeed_xdma_client *client = file->private_data;
+
+	if (client->ctx->current_client == client)
+		client->ctx->current_client = NULL;
+
+	kfree(client);
+	return 0;
+}
+
+static const struct file_operations aspeed_xdma_fops = {
+	.owner			= THIS_MODULE,
+	.write			= aspeed_xdma_write,
+	.poll			= aspeed_xdma_poll,
+	.mmap			= aspeed_xdma_mmap,
+	.open			= aspeed_xdma_open,
+	.release		= aspeed_xdma_release,
+};
+
 static int aspeed_xdma_init_mem(struct aspeed_xdma *ctx)
 {
 	int rc;
@@ -360,12 +625,26 @@ static int aspeed_xdma_init_mem(struct aspeed_xdma *ctx)
 		return -ENOMEM;
 	}
 
+	aspeed_xdma_free_vga_blk(ctx, ctx->vga_phys, ctx->vga_size);
+	aspeed_xdma_alloc_vga_blk(ctx, XDMA_CMDQ_SIZE);
+
 	dev_dbg(ctx->dev, "VGA mapped at phys[%08x], size[%08x].\n",
 		ctx->vga_phys, ctx->vga_size);
 
 	return 0;
 }
 
+static void aspeed_xdma_free_vga_blks(struct aspeed_xdma *ctx)
+{
+	struct aspeed_xdma_vga_blk *free;
+	struct aspeed_xdma_vga_blk *tmp;
+
+	list_for_each_entry_safe(free, tmp, &ctx->vga_blks_free, list) {
+		list_del(&free->list);
+		kfree(free);
+	}
+}
+
 static int aspeed_xdma_probe(struct platform_device *pdev)
 {
 	int irq;
@@ -380,6 +659,9 @@ static int aspeed_xdma_probe(struct platform_device *pdev)
 	ctx->dev = dev;
 	platform_set_drvdata(pdev, ctx);
 	init_waitqueue_head(&ctx->wait);
+	mutex_init(&ctx->list_lock);
+	mutex_init(&ctx->start_lock);
+	INIT_LIST_HEAD(&ctx->vga_blks_free);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	ctx->base = devm_ioremap_resource(dev, res);
@@ -425,6 +707,22 @@ static int aspeed_xdma_probe(struct platform_device *pdev)
 
 	aspeed_xdma_init_eng(ctx);
 
+	ctx->misc.minor = MISC_DYNAMIC_MINOR;
+	ctx->misc.fops = &aspeed_xdma_fops;
+	ctx->misc.name = "xdma";
+	ctx->misc.parent = dev;
+	rc = misc_register(&ctx->misc);
+	if (rc) {
+		dev_err(dev, "Unable to register xdma miscdevice\n");
+
+		aspeed_xdma_free_vga_blks(ctx);
+		dma_free_coherent(dev, ctx->vga_size, ctx->vga_virt,
+				  ctx->vga_dma);
+		dma_release_declared_memory(dev);
+		reset_control_assert(ctx->reset);
+		return rc;
+	}
+
 	return 0;
 }
 
@@ -432,6 +730,9 @@ static int aspeed_xdma_remove(struct platform_device *pdev)
 {
 	struct aspeed_xdma *ctx = platform_get_drvdata(pdev);
 
+	misc_deregister(&ctx->misc);
+
+	aspeed_xdma_free_vga_blks(ctx);
 	dma_free_coherent(ctx->dev, ctx->vga_size, ctx->vga_virt,
 			  ctx->vga_dma);
 	dma_release_declared_memory(ctx->dev);
-- 
1.8.3.1

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