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Subject[PATCH RFC v3 05/14] dmaengine: add dma_request support functions
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In order to provide a lockless submission path, the request context needs
to be pre-allocated rather than pulling from a memory pool.
Use the common request allocation call request_from_pages_alloc() to
accomplish this. The sbitmap code will be used to get the next
free request context. This is a simplified version of what blk-mq does
(not sbitmap_queue). The config option DMA_ENGINE_REQUEST is added so that
only drivers that supports dma request would enable the code.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
drivers/dma/Kconfig | 6 +++
drivers/dma/Makefile | 1
drivers/dma/dma-request.c | 96 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/dmaengine.h | 57 +++++++++++++++++++++++++++
4 files changed, 160 insertions(+)
create mode 100644 drivers/dma/dma-request.c

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 6fa1eba9d477..52a3c2086dcb 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -56,6 +56,12 @@ config DMA_OF
depends on OF
select DMA_ENGINE

+config DMA_ENGINE_REQUEST
+ def_bool n
+ depends on DMA_ENGINE
+ select SBITMAP
+ select CONTEXT_ALLOC
+
#devices
config ALTERA_MSGDMA
tristate "Altera / Intel mSGDMA Engine"
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index 42d7e2fc64fa..f80720075399 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_DMA_ENGINE) += dmaengine.o
obj-$(CONFIG_DMA_VIRTUAL_CHANNELS) += virt-dma.o
obj-$(CONFIG_DMA_ACPI) += acpi-dma.o
obj-$(CONFIG_DMA_OF) += of-dma.o
+obj-$(CONFIG_DMA_ENGINE_REQUEST) += dma-request.o

#dmatest
obj-$(CONFIG_DMATEST) += dmatest.o
diff --git a/drivers/dma/dma-request.c b/drivers/dma/dma-request.c
new file mode 100644
index 000000000000..43462fadf777
--- /dev/null
+++ b/drivers/dma/dma-request.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Copyright(c) 2019 Intel Corporation. All rights reserved. */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+#include <linux/device.h>
+#include <linux/dmaengine.h>
+#include <linux/mempool.h>
+
+struct dma_request *dma_chan_alloc_request(struct dma_chan *chan)
+{
+ int nr;
+ struct dma_request *req;
+
+ nr = sbitmap_get(&chan->sbmap, 0, false);
+ if (nr < 0)
+ return NULL;
+
+ req = chan->rqs[nr];
+ req->rq_private = NULL;
+ req->callback = NULL;
+ memset(&req->result, 0, sizeof(struct dmaengine_result));
+ return req;
+}
+EXPORT_SYMBOL_GPL(dma_chan_alloc_request);
+
+void dma_chan_free_request(struct dma_chan *chan, struct dma_request *rq)
+{
+ sbitmap_clear_bit(&chan->sbmap, rq->id);
+}
+EXPORT_SYMBOL_GPL(dma_chan_free_request);
+
+void dma_chan_free_request_resources(struct dma_chan *chan)
+{
+ context_free_from_pages(&chan->page_list);
+ kfree(chan->rqs);
+}
+EXPORT_SYMBOL_GPL(dma_chan_free_request_resources);
+
+static void dma_chan_assign_request(void *ctx, void *ptr, int idx)
+{
+ struct dma_chan *chan = (struct dma_chan *)ctx;
+ struct dma_request *rq = ptr;
+
+ chan->rqs[idx] = rq;
+}
+
+int dma_chan_alloc_request_resources(struct dma_chan *chan)
+{
+ int i, node, rc, id = 0;
+ size_t rq_size;
+
+ /* Requests are already allocated */
+ if (chan->rqs)
+ return 0;
+
+ node = dev_to_node(chan->device->dev);
+ rc = sbitmap_init_node(&chan->sbmap, chan->depth, -1,
+ GFP_KERNEL, node);
+ if (rc < 0)
+ return rc;
+
+ chan->rqs = kcalloc_node(chan->depth, sizeof(struct dma_request *),
+ GFP_KERNEL, node);
+ if (!chan->rqs) {
+ rc = -ENOMEM;
+ goto fail;
+ }
+
+ INIT_LIST_HEAD(&chan->page_list);
+
+ rq_size = round_up(sizeof(struct dma_request) +
+ chan->max_sgs * sizeof(struct scatterlist),
+ cache_line_size());
+
+ rc = context_alloc_from_pages((void *)chan, chan->depth, rq_size,
+ &chan->page_list, 4, node,
+ dma_chan_assign_request);
+ if (rc < 0)
+ goto fail;
+
+ for (i = 0; i < rc; i++) {
+ struct dma_request *rq = chan->rqs[i];
+
+ rq->id = id++;
+ rq->chan = chan;
+ }
+
+ return 0;
+
+ fail:
+ sbitmap_free(&chan->sbmap);
+ dma_chan_free_request_resources(chan);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(dma_chan_alloc_request_resources);
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 0202d44a17a5..7bc8c3f8283f 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -12,6 +12,8 @@
#include <linux/scatterlist.h>
#include <linux/bitmap.h>
#include <linux/types.h>
+#include <linux/sbitmap.h>
+#include <linux/bvec.h>
#include <asm/page.h>

/**
@@ -176,6 +178,8 @@ struct dma_interleaved_template {
* @DMA_PREP_CMD: tell the driver that the data passed to DMA API is command
* data and the descriptor should be in different format from normal
* data descriptors.
+ * @DMA_SUBMIT_NONBLOCK: tell the driver do not wait for resources if submit
+ * is not possible.
*/
enum dma_ctrl_flags {
DMA_PREP_INTERRUPT = (1 << 0),
@@ -186,6 +190,7 @@ enum dma_ctrl_flags {
DMA_PREP_FENCE = (1 << 5),
DMA_CTRL_REUSE = (1 << 6),
DMA_PREP_CMD = (1 << 7),
+ DMA_SUBMIT_NONBLOCK = (1 << 8),
};

/**
@@ -268,6 +273,13 @@ struct dma_chan {
struct dma_router *router;
void *route_data;

+ /* DMA request */
+ int max_sgs;
+ int depth;
+ struct sbitmap sbmap;
+ struct dma_request **rqs;
+ struct list_head page_list;
+
void *private;
};

@@ -511,6 +523,25 @@ struct dma_async_tx_descriptor {
#endif
};

+struct dma_request {
+ int id;
+ struct dma_chan *chan;
+ enum dma_transaction_type cmd;
+ enum dma_ctrl_flags flags;
+ struct bio_vec bvec;
+ dma_addr_t pg_dma;
+ int sg_nents;
+ void *rq_private;
+
+ /* Set by driver */
+ dma_async_tx_callback_result callback;
+ struct dmaengine_result result;
+ void *callback_param;
+
+ /* Leave as last member for flexible array of scatterlist */
+ struct scatterlist sg[];
+};
+
#ifdef CONFIG_DMA_ENGINE
static inline void dma_set_unmap(struct dma_async_tx_descriptor *tx,
struct dmaengine_unmap_data *unmap)
@@ -1359,6 +1390,32 @@ static inline int dma_get_slave_caps(struct dma_chan *chan,
}
#endif

+#ifdef CONFIG_DMA_ENGINE_REQUEST
+struct dma_request *dma_chan_alloc_request(struct dma_chan *chan);
+void dma_chan_free_request(struct dma_chan *chan, struct dma_request *rq);
+void dma_chan_free_request_resources(struct dma_chan *chan);
+int dma_chan_alloc_request_resources(struct dma_chan *chan);
+#else
+static inline struct dma_request *dma_chan_alloc_request(struct dma_chan *chan)
+{
+ return NULL;
+}
+
+static inline void dma_chan_free_request(struct dma_chan *chan,
+ struct dma_request *rq)
+{
+}
+
+static inline void dma_chan_free_request_resources(struct dma_chan *chan)
+{
+}
+
+static inline int dma_chan_alloc_request_resources(struct dma_chan *chan)
+{
+ return -EOPNOTSUPP;
+}
+#endif
+
#define dma_request_slave_channel_reason(dev, name) dma_request_chan(dev, name)

static inline int dmaengine_desc_set_reuse(struct dma_async_tx_descriptor *tx)
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