[PATCH 2/3] dmaengine: Add core function and capability check for DMA_MEMCPY_SG

Adrian Larumbe
2021-11-01T18:31:41Z

This is the old DMA_SG interface that was removed in commit
c678fa66341c ("dmaengine: remove DMA_SG as it is dead code in kernel"). It
has been renamed to DMA_MEMCPY_SG to better match the MEMSET and MEMSET_SG
naming convention.

It should only be used for mem2mem copies, either main system memory or
CPU-addressable device memory (like video memory on a PCI graphics card).

Bringing back this interface was prompted by the need to use the Xilinx
CDMA device for mem2mem SG transfers.

Signed-off-by: Adrian Larumbe <adrianml@alumnos.upm.es>
---
drivers/dma/dmaengine.c | 7 +++++++
include/linux/dmaengine.h | 20 ++++++++++++++++++++
2 files changed, 27 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index d9f7c097cfd6..2cfa8458b51b 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -1159,6 +1159,13 @@ int dma_async_device_register(struct dma_device *device)
return -EIO;
}

+ if (dma_has_cap(DMA_MEMCPY_SG, device->cap_mask) && !device->device_prep_dma_memcpy_sg) {
+ dev_err(device->dev,
+ "Device claims capability %s, but op is not defined\n",
+ "DMA_MEMCPY_SG");
+ return -EIO;
+ }
+
if (dma_has_cap(DMA_XOR, device->cap_mask) && !device->device_prep_dma_xor) {
dev_err(device->dev,
"Device claims capability %s, but op is not defined\n",
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 9000f3ffce8b..554a86665de9 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -50,6 +50,7 @@ enum dma_status {
*/
enum dma_transaction_type {
DMA_MEMCPY,
+ DMA_MEMCPY_SG,
DMA_XOR,
DMA_PQ,
DMA_XOR_VAL,
@@ -891,6 +892,11 @@ struct dma_device {
struct dma_async_tx_descriptor *(*device_prep_dma_memcpy)(
struct dma_chan *chan, dma_addr_t dst, dma_addr_t src,
size_t len, unsigned long flags);
+ struct dma_async_tx_descriptor *(*device_prep_dma_memcpy_sg)(
+ struct dma_chan *chan,
+ struct scatterlist *dst_sg, unsigned int dst_nents,
+ struct scatterlist *src_sg, unsigned int src_nents,
+ unsigned long flags);
struct dma_async_tx_descriptor *(*device_prep_dma_xor)(
struct dma_chan *chan, dma_addr_t dst, dma_addr_t *src,
unsigned int src_cnt, size_t len, unsigned long flags);
@@ -1051,6 +1057,20 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_memcpy(
len, flags);
}

+static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_memcpy_sg(
+ struct dma_chan *chan,
+ struct scatterlist *dst_sg, unsigned int dst_nents,
+ struct scatterlist *src_sg, unsigned int src_nents,
+ unsigned long flags)
+{
+ if (!chan || !chan->device || !chan->device->device_prep_dma_memcpy_sg)
+ return NULL;
+
+ return chan->device->device_prep_dma_memcpy_sg(chan, dst_sg, dst_nents,
+ src_sg, src_nents,
+ flags);
+}
+
static inline bool dmaengine_is_metadata_mode_supported(struct dma_chan *chan,
enum dma_desc_metadata_mode mode)
{
--
2.33.1