RE: [PATCH v7 1/8] Talitos: Support for async_tx XOR offload

On Thu, 9 Aug 2012 11:20:48 +0300, qiang.liu@freescale.com wrote:

From: Qiang Liu <redacted>
=20
Expose Talitos's XOR functionality to be used for RAID parity
calculation via the Async_tx layer.
=20
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Dipen Dudhat <redacted>
Signed-off-by: Maneesh Gupta <redacted>
Signed-off-by: Kim Phillips <redacted>
Signed-off-by: Vishnu Suresh <redacted>
Signed-off-by: Qiang Liu <redacted>
---
 drivers/crypto/Kconfig   |    9 +
 drivers/crypto/talitos.c |  413 ++++++++++++++++++++++++++++++++++++++++=

++++++

 drivers/crypto/talitos.h |   53 ++++++
 3 files changed, 475 insertions(+), 0 deletions(-)

+static void talitos_xor_run_tx_complete_actions(struct talitos_xor_desc =

*desc,

+		struct talitos_xor_chan *xor_chan)
+{
+	struct device *dev =3D xor_chan->dev;
+	dma_addr_t dest, addr;
+	unsigned int src_cnt =3D desc->unmap_src_cnt;
+	unsigned int len =3D desc->unmap_len;
+	enum dma_ctrl_flags flags =3D desc->async_tx.flags;
+	struct dma_async_tx_descriptor *tx =3D &desc->async_tx;
+
+	/* unmap dma addresses */
+	dest =3D desc->hwdesc.ptr[6].ptr;
+	if (likely(!(flags & DMA_COMPL_SKIP_DEST_UNMAP)))
+		dma_unmap_page(dev, dest, len, DMA_BIDIRECTIONAL);
+
+	desc->idx =3D 6 - src_cnt;
+	if (likely(!(flags & DMA_COMPL_SKIP_SRC_UNMAP))) {
+		while(desc->idx < 6) {
+			addr =3D desc->hwdesc.ptr[desc->idx++].ptr;
+			if (addr =3D=3D dest)
+				continue;
+			dma_unmap_page(dev, addr, len, DMA_TO_DEVICE);
+		}
+	}

No need for braces around the while block.

+	/* run dependent operations */
+	dma_run_dependencies(tx);
+}

+static void talitos_release_xor(struct device *dev, struct talitos_desc =

*hwdesc,

+				void *context, int error)
+{
+	struct talitos_xor_desc *desc =3D context;
+	struct talitos_xor_chan *xor_chan;
+	dma_async_tx_callback callback;
+	void *callback_param;
+
+	if (unlikely(error))
+		dev_err(dev, "xor operation: talitos error %d\n", error);
+
+	xor_chan =3D container_of(desc->async_tx.chan, struct talitos_xor_chan,
+				common);
+	spin_lock_bh(&xor_chan->desc_lock);
+	if (xor_chan->completed_cookie < desc->async_tx.cookie)
+		xor_chan->completed_cookie =3D desc->async_tx.cookie;
+
+	callback =3D desc->async_tx.callback;
+	callback_param =3D desc->async_tx.callback_param;
+
+	if (callback) {
+		spin_unlock_bh(&xor_chan->desc_lock);
+		callback(callback_param);
+		spin_lock_bh(&xor_chan->desc_lock);
+	}

Since callback_param is used only here, maybe:

if (callback) {
	void *callback_param =3D desc->async_tx.callback_param;

	spin_unlock_bh(&xor_chan->desc_lock);
	callback(callback_param);
	spin_lock_bh(&xor_chan->desc_lock);
}

+
+	talitos_xor_run_tx_complete_actions(desc, xor_chan);
+
+	list_del(&desc->node);
+	list_add_tail(&desc->node, &xor_chan->free_desc);
+	spin_unlock_bh(&xor_chan->desc_lock);
+	if (!list_empty(&xor_chan->pending_q))
+		talitos_process_pending(xor_chan);
+}

+static int talitos_alloc_chan_resources(struct dma_chan *chan)
+{
+	struct talitos_xor_chan *xor_chan;
+	struct talitos_xor_desc *desc;
+	LIST_HEAD(tmp_list);
+	int i;
+
+	xor_chan =3D container_of(chan, struct talitos_xor_chan, common);
+
+	if (!list_empty(&xor_chan->free_desc))
+		return xor_chan->total_desc;
+
+	for (i =3D 0; i < TALITOS_MAX_DESCRIPTOR_NR; i++) {
+		desc =3D talitos_xor_alloc_descriptor(xor_chan,
+				GFP_KERNEL | GFP_DMA);

talitos_xor_alloc_descriptor() is called here without holding
the xor_chan->desc_lock and it increments xor_chan->total_desc.
Isn't this an issue ?

+		if (!desc) {
+			dev_err(xor_chan->common.device->dev,
+				"Only %d initial descriptors\n", i);
+			break;
+		}
+		list_add_tail(&desc->node, &tmp_list);
+	}
+
+	if (!i)
+		return -ENOMEM;
+
+	/* At least one desc is allocated */
+	spin_lock_bh(&xor_chan->desc_lock);
+	list_splice_init(&tmp_list, &xor_chan->free_desc);
+	spin_unlock_bh(&xor_chan->desc_lock);
+
+	return xor_chan->total_desc;
+}

+/**
+ * talitos_register_dma_async - Initialize the Freescale XOR ADMA device
+ * It is registered as a DMA device with the capability to perform
+ * XOR operation with the Async_tx layer.
+ * The various queues and channel resources are also allocated.
+ */
+static int talitos_register_async_tx(struct device *dev, int max_xor_src=

s)

+{
+	struct talitos_private *priv =3D dev_get_drvdata(dev);
+	struct dma_device *dma_dev =3D &priv->dma_dev_common;
+	struct talitos_xor_chan *xor_chan;
+	int err;
+
+	xor_chan =3D kzalloc(sizeof(struct talitos_xor_chan), GFP_KERNEL);
+	if (!xor_chan) {
+		dev_err(dev, "unable to allocate xor channel\n");
+		return -ENOMEM;
+	}
+
+	dma_dev->dev =3D dev;
+	dma_dev->device_alloc_chan_resources =3D talitos_alloc_chan_resources;
+	dma_dev->device_free_chan_resources =3D talitos_free_chan_resources;
+	dma_dev->device_prep_dma_xor =3D talitos_prep_dma_xor;
+	dma_dev->max_xor =3D max_xor_srcs;
+	dma_dev->device_tx_status =3D talitos_is_tx_complete;
+	dma_dev->device_issue_pending =3D talitos_issue_pending;
+	INIT_LIST_HEAD(&dma_dev->channels);
+	dma_cap_set(DMA_XOR, dma_dev->cap_mask);
+
+	xor_chan->dev =3D dev;
+	xor_chan->common.device =3D dma_dev;
+	xor_chan->total_desc =3D 0;
+	INIT_LIST_HEAD(&xor_chan->submit_q);
+	INIT_LIST_HEAD(&xor_chan->pending_q);
+	INIT_LIST_HEAD(&xor_chan->in_progress_q);
+	INIT_LIST_HEAD(&xor_chan->free_desc);
+	spin_lock_init(&xor_chan->desc_lock);
+
+	list_add_tail(&xor_chan->common.device_node, &dma_dev->channels);
+	dma_dev->chancnt++;
+
+	err =3D dma_async_device_register(dma_dev);
+	if (err) {
+		dev_err(dev, "Unable to register XOR with Async_tx\n");
+		goto err_out;

Replace the jump with talitos_unregister_async_xor(dev) and
remove code under err_out label.

+	}
+
+	return err;
+
+err_out:
+	talitos_unregister_async_xor(dev);
+	return err;
+}
+#endif

This refers only to xor descriptors, so renaming it similar to
TALITOS_MAX_XOR_DESCRIPTOR_NR would make sense.

Besides these:
1. As Dan Williams mentioned, you should explain why you are using
both spin_lock_bh and spin_lock_irqsave on the same lock.
2. I don't see anything added to talitos_remove(). Shouldn't
talitos_unregister_async_xor() be called? Anything else?
Have you tested with talitos built as a module?

Horia