This patch changes the driver to allocate DMA descriptors when
needed. This stops memory resources to be wasted and letting
them sit idle in the free_list structure when the device doesn't
need it... This also solves the problem, that a driver has to
guess the number of how many descriptors it needs to allocate
in advance. Currently, the dma engine will just fail when put
under load by sata_dwc_460ex.
Signed-off-by: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx>
---
This patch is based on Andy Shevchenko's tree. It applies
on top of his "Fixes / cleanups in dw dmac" series.
I'm happy to report that these patches (together with the work
done by Mans) have made it possible to use sata_dwc_460ex driver
together with the DesignWare DMA engine on a current kernel.
This allows devices like Western Digital's MyBook Live or
Netgear's WNDR4700/4720 to work properly. Support for the
AmigaOne 500 is on the way as well.
---
drivers/dma/dw/core.c | 161 +++++++++++++++-----------------------------------
drivers/dma/dw/regs.h | 1 -
2 files changed, 47 insertions(+), 115 deletions(-)
diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 2b994dc..4c426ce 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -58,13 +58,6 @@
| DWC_CTLL_SMS(_sms)); \
})
-/*
- * Number of descriptors to allocate for each channel. This should be
- * made configurable somehow; preferably, the clients (at least the
- * ones using slave transfers) should be able to give us a hint.
- */
-#define NR_DESCS_PER_CHANNEL 64
-
/* The set of bus widths supported by the DMA controller */
#define DW_DMA_BUSWIDTHS \
BIT(DMA_SLAVE_BUSWIDTH_UNDEFINED) | \
@@ -84,51 +77,65 @@ static struct dw_desc *dwc_first_active(struct dw_dma_chan *dwc)
return to_dw_desc(dwc->active_list.next);
}
-static struct dw_desc *dwc_desc_get(struct dw_dma_chan *dwc)
+static dma_cookie_t dwc_tx_submit(struct dma_async_tx_descriptor *tx)
{
- struct dw_desc *desc, *_desc;
- struct dw_desc *ret = NULL;
- unsigned int i = 0;
- unsigned long flags;
+ struct dw_desc *desc = txd_to_dw_desc(tx);
+ struct dw_dma_chan *dwc = to_dw_dma_chan(tx->chan);
+ dma_cookie_t cookie;
+ unsigned long flags;
spin_lock_irqsave(&dwc->lock, flags);
- list_for_each_entry_safe(desc, _desc, &dwc->free_list, desc_node) {
- i++;
- if (async_tx_test_ack(&desc->txd)) {
- list_del(&desc->desc_node);
- ret = desc;
- break;
- }
- dev_dbg(chan2dev(&dwc->chan), "desc %p not ACKed\n", desc);
- }
+ cookie = dma_cookie_assign(tx);
+
+ /*
+ * REVISIT: We should attempt to chain as many descriptors as
+ * possible, perhaps even appending to those already submitted
+ * for DMA. But this is hard to do in a race-free manner.
+ */
+
+ dev_vdbg(chan2dev(tx->chan), "%s: queued %u\n", __func__, desc->txd.cookie);
+ list_add_tail(&desc->desc_node, &dwc->queue);
+
spin_unlock_irqrestore(&dwc->lock, flags);
- dev_vdbg(chan2dev(&dwc->chan), "scanned %u descriptors on freelist\n", i);
+ return cookie;
+}
- return ret;
+static struct dw_desc *dwc_desc_get(struct dw_dma_chan *dwc)
+{
+ struct dw_dma *dw = to_dw_dma(dwc->chan.device);
+ struct dw_desc *desc;
+ dma_addr_t phys;
+
+ desc = dma_pool_zalloc(dw->desc_pool, GFP_ATOMIC, &phys);
+ if (!desc)
+ return NULL;
+
+ dwc->descs_allocated++;
+ INIT_LIST_HEAD(&desc->tx_list);
+ dma_async_tx_descriptor_init(&desc->txd, &dwc->chan);
+ desc->txd.tx_submit = dwc_tx_submit;
+ desc->txd.flags = DMA_CTRL_ACK;
+ desc->txd.phys = phys;
+ return desc;
}
-/*
- * Move a descriptor, including any children, to the free list.
- * `desc' must not be on any lists.
- */
static void dwc_desc_put(struct dw_dma_chan *dwc, struct dw_desc *desc)
{
- unsigned long flags;
+ struct dw_dma *dw = to_dw_dma(dwc->chan.device);
+ struct dw_desc *child, *_next;
- if (desc) {
- struct dw_desc *child;
+ if (unlikely(!desc))
+ return;
- spin_lock_irqsave(&dwc->lock, flags);
- list_for_each_entry(child, &desc->tx_list, desc_node)
- dev_vdbg(chan2dev(&dwc->chan),
- "moving child desc %p to freelist\n",
- child);
- list_splice_init(&desc->tx_list, &dwc->free_list);
- dev_vdbg(chan2dev(&dwc->chan), "moving desc %p to freelist\n", desc);
- list_add(&desc->desc_node, &dwc->free_list);
- spin_unlock_irqrestore(&dwc->lock, flags);
+ list_for_each_entry_safe(child, _next, &desc->tx_list, desc_node) {
+ list_del(&child->desc_node);
+ dma_pool_free(dw->desc_pool, child, child->txd.phys);
+ dwc->descs_allocated--;
}
+
+ dma_pool_free(dw->desc_pool, desc, desc->txd.phys);
+ dwc->descs_allocated--;
}
static void dwc_initialize(struct dw_dma_chan *dwc)
@@ -282,11 +289,7 @@ dwc_descriptor_complete(struct dw_dma_chan *dwc, struct dw_desc *desc,
list_for_each_entry(child, &desc->tx_list, desc_node)
async_tx_ack(&child->txd);
async_tx_ack(&desc->txd);
-
- list_splice_init(&desc->tx_list, &dwc->free_list);
- list_move(&desc->desc_node, &dwc->free_list);
-
- dma_descriptor_unmap(txd);
+ dwc_desc_put(dwc, desc);
spin_unlock_irqrestore(&dwc->lock, flags);
if (callback)
@@ -648,30 +651,6 @@ static irqreturn_t dw_dma_interrupt(int irq, void *dev_id)
/*----------------------------------------------------------------------*/
-static dma_cookie_t dwc_tx_submit(struct dma_async_tx_descriptor *tx)
-{
- struct dw_desc *desc = txd_to_dw_desc(tx);
- struct dw_dma_chan *dwc = to_dw_dma_chan(tx->chan);
- dma_cookie_t cookie;
- unsigned long flags;
-
- spin_lock_irqsave(&dwc->lock, flags);
- cookie = dma_cookie_assign(tx);
-
- /*
- * REVISIT: We should attempt to chain as many descriptors as
- * possible, perhaps even appending to those already submitted
- * for DMA. But this is hard to do in a race-free manner.
- */
-
- dev_vdbg(chan2dev(tx->chan), "%s: queued %u\n", __func__, desc->txd.cookie);
- list_add_tail(&desc->desc_node, &dwc->queue);
-
- spin_unlock_irqrestore(&dwc->lock, flags);
-
- return cookie;
-}
-
static struct dma_async_tx_descriptor *
dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
size_t len, unsigned long flags)
@@ -1133,9 +1112,7 @@ static int dwc_alloc_chan_resources(struct dma_chan *chan)
{
struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
struct dw_dma *dw = to_dw_dma(chan->device);
- struct dw_desc *desc;
int i;
- unsigned long flags;
dev_vdbg(chan2dev(chan), "%s\n", __func__);
@@ -1166,48 +1143,15 @@ static int dwc_alloc_chan_resources(struct dma_chan *chan)
dw_dma_on(dw);
dw->in_use |= dwc->mask;
- spin_lock_irqsave(&dwc->lock, flags);
- i = dwc->descs_allocated;
- while (dwc->descs_allocated < NR_DESCS_PER_CHANNEL) {
- dma_addr_t phys;
-
- spin_unlock_irqrestore(&dwc->lock, flags);
-
- desc = dma_pool_alloc(dw->desc_pool, GFP_ATOMIC, &phys);
- if (!desc)
- goto err_desc_alloc;
-
- memset(desc, 0, sizeof(struct dw_desc));
-
- INIT_LIST_HEAD(&desc->tx_list);
- dma_async_tx_descriptor_init(&desc->txd, chan);
- desc->txd.tx_submit = dwc_tx_submit;
- desc->txd.flags = DMA_CTRL_ACK;
- desc->txd.phys = phys;
-
- dwc_desc_put(dwc, desc);
-
- spin_lock_irqsave(&dwc->lock, flags);
- i = ++dwc->descs_allocated;
- }
-
- spin_unlock_irqrestore(&dwc->lock, flags);
-
dev_dbg(chan2dev(chan), "%s: allocated %d descriptors\n", __func__, i);
return i;
-
-err_desc_alloc:
- dev_info(chan2dev(chan), "only allocated %d descriptors\n", i);
-
- return i;
}
static void dwc_free_chan_resources(struct dma_chan *chan)
{
struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
struct dw_dma *dw = to_dw_dma(chan->device);
- struct dw_desc *desc, *_desc;
unsigned long flags;
LIST_HEAD(list);
@@ -1220,8 +1164,6 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
BUG_ON(dma_readl(to_dw_dma(chan->device), CH_EN) & dwc->mask);
spin_lock_irqsave(&dwc->lock, flags);
- list_splice_init(&dwc->free_list, &list);
- dwc->descs_allocated = 0;
/* Clear custom channel configuration */
dwc->src_id = 0;
@@ -1244,11 +1186,6 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
if (!dw->in_use)
dw_dma_off(dw);
- list_for_each_entry_safe(desc, _desc, &list, desc_node) {
- dev_vdbg(chan2dev(chan), " freeing descriptor %p\n", desc);
- dma_pool_free(dw->desc_pool, desc, desc->txd.phys);
- }
-
dev_vdbg(chan2dev(chan), "%s: done\n", __func__);
}
@@ -1380,9 +1317,6 @@ struct dw_cyclic_desc *dw_dma_cyclic_prep(struct dma_chan *chan,
retval = ERR_PTR(-ENOMEM);
- if (periods > NR_DESCS_PER_CHANNEL)
- goto out_err;
-
cdesc = kzalloc(sizeof(struct dw_cyclic_desc), GFP_KERNEL);
if (!cdesc)
goto out_err;
@@ -1613,7 +1547,6 @@ int dw_dma_probe(struct dw_dma_chip *chip)
INIT_LIST_HEAD(&dwc->active_list);
INIT_LIST_HEAD(&dwc->queue);
- INIT_LIST_HEAD(&dwc->free_list);
channel_clear_bit(dw, CH_EN, dwc->mask);
diff --git a/drivers/dma/dw/regs.h b/drivers/dma/dw/regs.h
index 5b3ea2d..4b7bd78 100644
--- a/drivers/dma/dw/regs.h
+++ b/drivers/dma/dw/regs.h
@@ -236,7 +236,6 @@ struct dw_dma_chan {
unsigned long flags;
struct list_head active_list;
struct list_head queue;
- struct list_head free_list;
struct dw_cyclic_desc *cdesc;
unsigned int descs_allocated;
--
2.8.0.rc3
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