[PATCH v2] net: ethernet: ti: cpdma: switch to use genalloc

[Grygorii Strashko]

TI CPDMA currently uses a bitmap for tracking descriptors alloactions
allocations, but The genalloc already handles the same and can be used
as with special memory (SRAM) as with DMA cherent memory chank
(dma_alloc_coherent()). Hence, switch to using genalloc and add
desc_num property for each channel for limitation of max number of
allowed descriptors for each CPDMA channel. This patch do not affect
on net throuput.

Tested-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> 
Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
---
Testing
TCP window: 256K, bandwidth in Mbits/sec:
 host: iperf -s
 device: iperf -c  172.22.39.17 -t600 -i5 -d -w128K

AM437x-idk, 1Gbps link
 before: : 341.60, after: 232+123=355
am57xx-beagle-x15, 1Gbps link
 before: : 1112.80, after: 814+321=1135
am335x-boneblack, 100Mbps link
 before: : 162.40, after: 72+93=165

changes in v2:
 - reverted change in desc_phys() to keep am3517 which has separate CPPI
   addresses from EMAC and CPU perspective
 - minor format changes.

link on v1:
 https://lkml.org/lkml/2016/6/23/353

 drivers/net/ethernet/ti/davinci_cpdma.c | 132 +++++++++++++++-----------------
 1 file changed, 60 insertions(+), 72 deletions(-)

diff --git a/drivers/net/ethernet/ti/davinci_cpdma.c b/drivers/net/ethernet/ti/davinci_cpdma.c
index 63b3009..b40a402 100644
--- a/drivers/net/ethernet/ti/davinci_cpdma.c
+++ b/drivers/net/ethernet/ti/davinci_cpdma.c
@@ -21,7 +21,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/io.h>
 #include <linux/delay.h>
-
+#include <linux/genalloc.h>
 #include "davinci_cpdma.h"
 
 /* DMA Registers */
@@ -87,9 +87,8 @@ struct cpdma_desc_pool {
 	void			*cpumap;	/* dma_alloc map */
 	int			desc_size, mem_size;
 	int			num_desc, used_desc;
-	unsigned long		*bitmap;
 	struct device		*dev;
-	spinlock_t		lock;
+	struct gen_pool		*gen_pool;
 };
 
 enum cpdma_state {
@@ -117,6 +116,7 @@ struct cpdma_chan {
 	int				chan_num;
 	spinlock_t			lock;
 	int				count;
+	u32				desc_num;
 	u32				mask;
 	cpdma_handler_fn		handler;
 	enum dma_data_direction		dir;
@@ -145,6 +145,20 @@ struct cpdma_chan {
 				 (directed << CPDMA_TO_PORT_SHIFT));	\
 	} while (0)
 
+static void cpdma_desc_pool_destroy(struct cpdma_desc_pool *pool)
+{
+	if (!pool)
+		return;
+
+	WARN_ON(pool->used_desc);
+	if (pool->cpumap) {
+		dma_free_coherent(pool->dev, pool->mem_size, pool->cpumap,
+				  pool->phys);
+	} else {
+		iounmap(pool->iomap);
+	}
+}
+
 /*
  * Utility constructs for a cpdma descriptor pool.  Some devices (e.g. davinci
  * emac) have dedicated on-chip memory for these descriptors.  Some other
@@ -155,24 +169,25 @@ static struct cpdma_desc_pool *
 cpdma_desc_pool_create(struct device *dev, u32 phys, dma_addr_t hw_addr,
 				int size, int align)
 {
-	int bitmap_size;
 	struct cpdma_desc_pool *pool;
+	int ret;
 
 	pool = devm_kzalloc(dev, sizeof(*pool), GFP_KERNEL);
 	if (!pool)
-		goto fail;
-
-	spin_lock_init(&pool->lock);
+		goto gen_pool_create_fail;
 
 	pool->dev	= dev;
 	pool->mem_size	= size;
 	pool->desc_size	= ALIGN(sizeof(struct cpdma_desc), align);
 	pool->num_desc	= size / pool->desc_size;
 
-	bitmap_size  = (pool->num_desc / BITS_PER_LONG) * sizeof(long);
-	pool->bitmap = devm_kzalloc(dev, bitmap_size, GFP_KERNEL);
-	if (!pool->bitmap)
-		goto fail;
+	pool->gen_pool = devm_gen_pool_create(dev, ilog2(pool->desc_size), -1,
+					      "cpdma");
+	if (IS_ERR(pool->gen_pool)) {
+		dev_err(dev, "pool create failed %ld\n",
+			PTR_ERR(pool->gen_pool));
+		goto gen_pool_create_fail;
+	}
 
 	if (phys) {
 		pool->phys  = phys;
@@ -185,24 +200,22 @@ cpdma_desc_pool_create(struct device *dev, u32 phys, dma_addr_t hw_addr,
 		pool->phys = pool->hw_addr; /* assumes no IOMMU, don't use this value */
 	}
 
-	if (pool->iomap)
-		return pool;
-fail:
-	return NULL;
-}
-
-static void cpdma_desc_pool_destroy(struct cpdma_desc_pool *pool)
-{
-	if (!pool)
-		return;
+	if (!pool->iomap)
+		goto gen_pool_create_fail;
 
-	WARN_ON(pool->used_desc);
-	if (pool->cpumap) {
-		dma_free_coherent(pool->dev, pool->mem_size, pool->cpumap,
-				  pool->phys);
-	} else {
-		iounmap(pool->iomap);
+	ret = gen_pool_add_virt(pool->gen_pool, (unsigned long)pool->iomap,
+				pool->phys, pool->mem_size, -1);
+	if (ret < 0) {
+		dev_err(dev, "pool add failed %d\n", ret);
+		goto gen_pool_add_virt_fail;
 	}
+
+	return pool;
+
+gen_pool_add_virt_fail:
+	cpdma_desc_pool_destroy(pool);
+gen_pool_create_fail:
+	return NULL;
 }
 
 static inline dma_addr_t desc_phys(struct cpdma_desc_pool *pool,
@@ -220,47 +233,23 @@ desc_from_phys(struct cpdma_desc_pool *pool, dma_addr_t dma)
 }
 
 static struct cpdma_desc __iomem *
-cpdma_desc_alloc(struct cpdma_desc_pool *pool, int num_desc, bool is_rx)
+cpdma_desc_alloc(struct cpdma_desc_pool *pool)
 {
-	unsigned long flags;
-	int index;
-	int desc_start;
-	int desc_end;
 	struct cpdma_desc __iomem *desc = NULL;
 
-	spin_lock_irqsave(&pool->lock, flags);
-
-	if (is_rx) {
-		desc_start = 0;
-		desc_end = pool->num_desc/2;
-	 } else {
-		desc_start = pool->num_desc/2;
-		desc_end = pool->num_desc;
-	}
-
-	index = bitmap_find_next_zero_area(pool->bitmap,
-				desc_end, desc_start, num_desc, 0);
-	if (index < desc_end) {
-		bitmap_set(pool->bitmap, index, num_desc);
-		desc = pool->iomap + pool->desc_size * index;
+	desc = (struct cpdma_desc __iomem *)gen_pool_alloc(pool->gen_pool,
+							   pool->desc_size);
+	if (desc)
 		pool->used_desc++;
-	}
 
-	spin_unlock_irqrestore(&pool->lock, flags);
 	return desc;
 }
 
 static void cpdma_desc_free(struct cpdma_desc_pool *pool,
 			    struct cpdma_desc __iomem *desc, int num_desc)
 {
-	unsigned long flags, index;
-
-	index = ((unsigned long)desc - (unsigned long)pool->iomap) /
-		pool->desc_size;
-	spin_lock_irqsave(&pool->lock, flags);
-	bitmap_clear(pool->bitmap, index, num_desc);
+	gen_pool_free(pool->gen_pool, (unsigned long)desc, pool->desc_size);
 	pool->used_desc--;
-	spin_unlock_irqrestore(&pool->lock, flags);
 }
 
 struct cpdma_ctlr *cpdma_ctlr_create(struct cpdma_params *params)
@@ -516,6 +505,7 @@ struct cpdma_chan *cpdma_chan_create(struct cpdma_ctlr *ctlr, int chan_num,
 	chan->state	= CPDMA_STATE_IDLE;
 	chan->chan_num	= chan_num;
 	chan->handler	= handler;
+	chan->desc_num = ctlr->pool->num_desc / 2;
 
 	if (is_rx_chan(chan)) {
 		chan->hdp	= ctlr->params.rxhdp + offset;
@@ -675,7 +665,13 @@ int cpdma_chan_submit(struct cpdma_chan *chan, void *token, void *data,
 		goto unlock_ret;
 	}
 
-	desc = cpdma_desc_alloc(ctlr->pool, 1, is_rx_chan(chan));
+	if (chan->count >= chan->desc_num)	{
+		chan->stats.desc_alloc_fail++;
+		ret = -ENOMEM;
+		goto unlock_ret;
+	}
+
+	desc = cpdma_desc_alloc(ctlr->pool);
 	if (!desc) {
 		chan->stats.desc_alloc_fail++;
 		ret = -ENOMEM;
@@ -722,24 +718,16 @@ EXPORT_SYMBOL_GPL(cpdma_chan_submit);
 
 bool cpdma_check_free_tx_desc(struct cpdma_chan *chan)
 {
-	unsigned long flags;
-	int index;
-	bool ret;
 	struct cpdma_ctlr	*ctlr = chan->ctlr;
 	struct cpdma_desc_pool	*pool = ctlr->pool;
+	bool			free_tx_desc;
+	unsigned long		flags;
 
-	spin_lock_irqsave(&pool->lock, flags);
-
-	index = bitmap_find_next_zero_area(pool->bitmap,
-				pool->num_desc, pool->num_desc/2, 1, 0);
-
-	if (index < pool->num_desc)
-		ret = true;
-	else
-		ret = false;
-
-	spin_unlock_irqrestore(&pool->lock, flags);
-	return ret;
+	spin_lock_irqsave(&chan->lock, flags);
+	free_tx_desc = (chan->count < chan->desc_num) &&
+			 gen_pool_avail(pool->gen_pool);
+	spin_unlock_irqrestore(&chan->lock, flags);
+	return free_tx_desc;
 }
 EXPORT_SYMBOL_GPL(cpdma_check_free_tx_desc);
 
-- 
2.9.0