Add a dmaengine API to retrieve slave SG transfer limits.
The API is optionally implemented by dmaengine drivers and when
unimplemented will return a NULL pointer. A client driver using
this API provides the required dma channel, address width, and
burst size of the transfer. dma_get_slave_sg_limits() returns an
SG limits structure with the maximum number and size of SG segments
that the given channel can handle.
Signed-off-by: Matt Porter <mpor...@ti.com>
---
include/linux/dmaengine.h | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 91ac8da..a4a6aac 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -371,6 +371,18 @@ struct dma_slave_config {
unsigned int slave_id;
};
+/* struct dma_slave_sg_limits - expose SG transfer limits of a channel
+ *
+ * @max_seg_nr: maximum number of SG segments supported on a SG/SLAVE
+ * channel (0 for no maximum or not a SG/SLAVE channel)
+ * @max_seg_len: maximum length of SG segments supported on a SG/SLAVE
+ * channel (0 for no maximum or not a SG/SLAVE channel)
+ */
+struct dma_slave_sg_limits {
+ u32 max_seg_nr;
+ u32 max_seg_len;
+};
+
static inline const char *dma_chan_name(struct dma_chan *chan)
{
return dev_name(&chan->dev->device);
@@ -534,6 +546,7 @@ struct dma_tx_state {
* struct with auxiliary transfer status information, otherwise the call
* will just return a simple status code
* @device_issue_pending: push pending transactions to hardware
+ * @device_slave_sg_limits: return the slave SG capabilities
*/
struct dma_device {
@@ -602,6 +615,9 @@ struct dma_device {
dma_cookie_t cookie,
struct dma_tx_state *txstate);
void (*device_issue_pending)(struct dma_chan *chan);
+ struct dma_slave_sg_limits *(*device_slave_sg_limits)(
+ struct dma_chan *chan, enum dma_slave_buswidth addr_width,
+ u32 maxburst);
};
static inline int dmaengine_device_control(struct dma_chan *chan,
@@ -963,6 +979,29 @@ dma_set_tx_state(struct dma_tx_state *st, dma_cookie_t
last, dma_cookie_t used,
}
}
+/**
+ * dma_get_slave_sg_limits - get DMAC SG transfer capabilities
+ * @chan: target DMA channel
+ * @addr_width: address width of the DMA transfer
+ * @maxburst: maximum DMA transfer burst size
+ *
+ * Get SG transfer capabilities for a specified channel. If the dmaengine
+ * driver does not implement SG transfer capabilities then NULL is
+ * returned.
+ */
+static inline struct dma_slave_sg_limits
+*dma_get_slave_sg_limits(struct dma_chan *chan,
+ enum dma_slave_buswidth addr_width,
+ u32 maxburst)
+{
+ if (chan->device->device_slave_sg_limits)
+ return chan->device->device_slave_sg_limits(chan,
+ addr_width,
+ maxburst);
+
+ return NULL;
+}
+
enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie);
#ifdef CONFIG_DMA_ENGINE
enum dma_status dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx);
--
1.7.9.5
--
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