Re: [PATCH v3 3/8] drivers/soc: xdma: Add user interface

Eduardo Valentin
2019-05-31T03:51:55Z

On Wed, May 29, 2019 at 01:10:03PM -0500, Eddie James wrote:
> 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, the
> VGA memory space is pooled and allocated with genalloc. Users calling
> mmap allocate pages from this pool for their usage. 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@linux.ibm.com>
> ---
> drivers/soc/aspeed/aspeed-xdma.c | 201 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 201 insertions(+)
>
> diff --git a/drivers/soc/aspeed/aspeed-xdma.c b/drivers/soc/aspeed/aspeed-xdma.c
> index 3dc0ce4..39f6545 100644
> --- a/drivers/soc/aspeed/aspeed-xdma.c
> +++ b/drivers/soc/aspeed/aspeed-xdma.c
> @@ -129,6 +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;
>
> @@ -140,6 +142,8 @@ struct aspeed_xdma {
> dma_addr_t cmdq_vga_phys;
> void *cmdq_vga_virt;
> struct gen_pool *vga_pool;
> +
> + struct miscdevice misc;
> };
>
> struct aspeed_xdma_client {
> @@ -331,6 +335,183 @@ static irqreturn_t aspeed_xdma_irq(int irq, void *arg)
> return IRQ_HANDLED;
> }
>
> +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;
> +
> + gen_pool_free(client->ctx->vga_pool, (unsigned long)client->virt,
> + client->size);
> +
> + client->virt = NULL;
> + 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->virt = gen_pool_dma_alloc(ctx->vga_pool, client->size,
> + &client->phys);
> + if (!client->virt) {
> + client->phys = 0;
> + 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) {
> + gen_pool_free(ctx->vga_pool, (unsigned long)client->virt,
> + client->size);
> +
> + client->virt = NULL;
> + client->phys = 0;
> + client->size = 0;
> + return rc;
> + }
> +
> + dev_dbg(ctx->dev, "mmap: v[%08lx] to p[%08x], s[%08x]\n",
> + vma->vm_start, (u32)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;
> @@ -431,6 +612,8 @@ 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);
>
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> ctx->base = devm_ioremap_resource(dev, res);
> @@ -482,6 +665,23 @@ 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";

tiny bit here, should this be named more specific ? something like "aspeed_xdma" ?

> + ctx->misc.parent = dev;
> + rc = misc_register(&ctx->misc);
> + if (rc) {
> + dev_err(dev, "Unable to register xdma miscdevice.\n");
> +
> + gen_pool_free(ctx->vga_pool, (unsigned long)ctx->cmdq_vga_virt,
> + XDMA_CMDQ_SIZE);
> + 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;
> }
>
> @@ -489,6 +689,7 @@ static int aspeed_xdma_remove(struct platform_device *pdev)
> {
> struct aspeed_xdma *ctx = platform_get_drvdata(pdev);
>
> + misc_deregister(&ctx->misc);
> gen_pool_free(ctx->vga_pool, (unsigned long)ctx->cmdq_vga_virt,
> XDMA_CMDQ_SIZE);
> dma_free_coherent(ctx->dev, ctx->vga_size, ctx->vga_virt,
> --
> 1.8.3.1
>

--
All the best,
Eduardo Valentin