[PATCH RFC 10/14] dmaengine: idxd: add descriptor manipulation routines

[Dave Jiang]

This commit adds helper functions for DSA descriptor allocation, setup,
submission, and free operations.

Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>

---

idxd_submit_desc() and idxd_alloc_desc() are used in the next patch in the
series.
---
 drivers/dma/idxd/Makefile |    2 -
 drivers/dma/idxd/submit.c |  127 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 128 insertions(+), 1 deletion(-)
 create mode 100644 drivers/dma/idxd/submit.c

diff --git a/drivers/dma/idxd/Makefile b/drivers/dma/idxd/Makefile
index a552560a03dc..50eca12015e2 100644
--- a/drivers/dma/idxd/Makefile
+++ b/drivers/dma/idxd/Makefile
@@ -1,2 +1,2 @@
 obj-$(CONFIG_INTEL_IDXD) += idxd.o
-idxd-y := init.o irq.o device.o sysfs.o
+idxd-y := init.o irq.o device.o sysfs.o submit.o
diff --git a/drivers/dma/idxd/submit.c b/drivers/dma/idxd/submit.c
new file mode 100644
index 000000000000..2dcd13f9f654
--- /dev/null
+++ b/drivers/dma/idxd/submit.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2019 Intel Corporation. All rights rsvd. */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/dmaengine.h>
+#include <uapi/linux/idxd.h>
+#include "../dmaengine.h"
+#include "idxd.h"
+#include "registers.h"
+
+static struct idxd_desc *idxd_alloc_desc(struct idxd_wq *wq, bool nonblock)
+{
+	struct idxd_desc *desc;
+	int idx;
+	struct idxd_device *idxd = wq->idxd;
+
+	if (idxd->state != IDXD_DEV_ENABLED)
+		return ERR_PTR(-EIO);
+
+	if (!nonblock)
+		percpu_down_read(&wq->submit_lock);
+	else if (!percpu_down_read_trylock(&wq->submit_lock))
+		return ERR_PTR(-EBUSY);
+
+	if (!atomic_add_unless(&wq->dq_count, 1, wq->size)) {
+		int rc;
+
+		if (nonblock) {
+			percpu_up_read(&wq->submit_lock);
+			return ERR_PTR(-EAGAIN);
+		}
+
+		percpu_up_read(&wq->submit_lock);
+		percpu_down_write(&wq->submit_lock);
+		rc = wait_event_interruptible(wq->submit_waitq,
+				atomic_add_unless(&wq->dq_count, 1, wq->size) ||
+				idxd->state != IDXD_DEV_ENABLED);
+		percpu_up_write(&wq->submit_lock);
+		if (rc < 0)
+			return ERR_PTR(-EINTR);
+		if (idxd->state != IDXD_DEV_ENABLED)
+			return ERR_PTR(-EIO);
+	} else {
+		percpu_up_read(&wq->submit_lock);
+	}
+
+	idx = sbitmap_get(&wq->sbmap, 0, false);
+	if (idx < 0) {
+		atomic_dec(&wq->dq_count);
+		return ERR_PTR(-EAGAIN);
+	}
+
+	desc = wq->descs[idx];
+	memset(desc->hw, 0, sizeof(struct dsa_hw_desc));
+	memset(desc->completion, 0, sizeof(struct dsa_completion_record));
+	return desc;
+}
+
+void idxd_free_desc(struct idxd_wq *wq, struct idxd_desc *desc)
+{
+	atomic_dec(&wq->dq_count);
+
+	sbitmap_clear_bit(&wq->sbmap, desc->id);
+	wake_up(&wq->submit_waitq);
+}
+
+static int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc,
+			    bool nonblock)
+{
+	struct idxd_device *idxd = wq->idxd;
+	int vec = desc->hw->int_handle;
+
+	if (idxd->state != IDXD_DEV_ENABLED)
+		return -EIO;
+
+	/*
+	 * The wmb() flushes writes to coherent DMA data before possibly
+	 * triggering a DMA read. The wmb() is necessary even on UP because
+	 * the recipient is a device.
+	 */
+	wmb();
+	iosubmit_cmds512(wq->dportal, desc->hw, 1);
+
+	/*
+	 * Pending the descriptor to the lockless list for the irq_entry
+	 * that we designated the descriptor to.
+	 */
+	llist_add(&desc->llnode, &idxd->irq_entries[vec].pending_llist);
+
+	return 0;
+}
+
+static inline void idxd_prep_desc_common(struct idxd_wq *wq,
+					 struct dsa_hw_desc *hw, char opcode,
+					 u64 addr_f1, u64 addr_f2, u64 len,
+					 u64 compl, u32 flags)
+{
+	hw->flags = flags;
+	hw->opcode = opcode;
+	hw->src_addr = addr_f1;
+	hw->dst_addr = addr_f2;
+	hw->xfer_size = len;
+	hw->priv = !!(wq->type == IDXD_WQT_KERNEL);
+	hw->completion_addr = compl;
+
+	/*
+	 * Descriptor completion vectors are 1-8 for MSIX. We will round
+	 * robin through the 8 vectors.
+	 */
+	hw->int_handle = ++wq->vec_ptr;
+	wq->vec_ptr = wq->vec_ptr & 7;
+}
+
+static inline void set_desc_addresses(struct dma_request *req,
+				      u64 *src, u64 *dst)
+{
+		*src = sg_dma_address(&req->sg[0]);
+		*dst = req->pg_dma;
+}
+
+static inline void set_completion_address(struct idxd_desc *desc,
+					  u64 *compl_addr)
+{
+		*compl_addr = desc->compl_dma;
+}