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Subject[PATCH v3 05/18] dmaengine: dma-jz4780: Use 4-word descriptors
Date
The only information we use in the 8-word version of the hardware DMA
descriptor that is not present in the 4-word version is the transfer
type, aka. the ID of the source or recipient device.

Since the transfer type will never change for a DMA channel in use,
we can just set it once for all in the corresponding DMA register
before starting any transfer.

This has several benefits:

* the driver will handle twice as many hardware DMA descriptors;

* the driver is closer to support the JZ4740, which only supports 4-word
hardware DMA descriptors;

* the JZ4770 SoC needs the transfer type to be set in the corresponding
DMA register anyway, even if 8-word descriptors are in use.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
---
drivers/dma/dma-jz4780.c | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)

v2: No change

v3: No change

diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index 2f17a0fb1e5c..23e92d153919 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/drivers/dma/dma-jz4780.c
@@ -95,17 +95,12 @@
* @dtc: transfer count (number of blocks of the transfer size specified in DCM
* to transfer) in the low 24 bits, offset of the next descriptor from the
* descriptor base address in the upper 8 bits.
- * @sd: target/source stride difference (in stride transfer mode).
- * @drt: request type
*/
struct jz4780_dma_hwdesc {
uint32_t dcm;
uint32_t dsa;
uint32_t dta;
uint32_t dtc;
- uint32_t sd;
- uint32_t drt;
- uint32_t reserved[2];
};

/* Size of allocations for hardware descriptor blocks. */
@@ -286,7 +281,6 @@ static int jz4780_dma_setup_hwdesc(struct jz4780_dma_chan *jzchan,
desc->dcm = JZ_DMA_DCM_SAI;
desc->dsa = addr;
desc->dta = config->dst_addr;
- desc->drt = jzchan->transfer_type;

width = config->dst_addr_width;
maxburst = config->dst_maxburst;
@@ -294,7 +288,6 @@ static int jz4780_dma_setup_hwdesc(struct jz4780_dma_chan *jzchan,
desc->dcm = JZ_DMA_DCM_DAI;
desc->dsa = config->src_addr;
desc->dta = addr;
- desc->drt = jzchan->transfer_type;

width = config->src_addr_width;
maxburst = config->src_maxburst;
@@ -439,9 +432,10 @@ static struct dma_async_tx_descriptor *jz4780_dma_prep_dma_memcpy(
tsz = jz4780_dma_transfer_size(dest | src | len,
&jzchan->transfer_shift);

+ jzchan->transfer_type = JZ_DMA_DRT_AUTO;
+
desc->desc[0].dsa = src;
desc->desc[0].dta = dest;
- desc->desc[0].drt = JZ_DMA_DRT_AUTO;
desc->desc[0].dcm = JZ_DMA_DCM_TIE | JZ_DMA_DCM_SAI | JZ_DMA_DCM_DAI |
tsz << JZ_DMA_DCM_TSZ_SHIFT |
JZ_DMA_WIDTH_32_BIT << JZ_DMA_DCM_SP_SHIFT |
@@ -496,9 +490,12 @@ static void jz4780_dma_begin(struct jz4780_dma_chan *jzchan)
(jzchan->curr_hwdesc + 1) % jzchan->desc->count;
}

- /* Use 8-word descriptors. */
- jz4780_dma_chn_writel(jzdma, jzchan->id,
- JZ_DMA_REG_DCS, JZ_DMA_DCS_DES8);
+ /* Use 4-word descriptors. */
+ jz4780_dma_chn_writel(jzdma, jzchan->id, JZ_DMA_REG_DCS, 0);
+
+ /* Set transfer type. */
+ jz4780_dma_chn_writel(jzdma, jzchan->id, JZ_DMA_REG_DRT,
+ jzchan->transfer_type);

/* Write descriptor address and initiate descriptor fetch. */
desc_phys = jzchan->desc->desc_phys +
@@ -508,7 +505,7 @@ static void jz4780_dma_begin(struct jz4780_dma_chan *jzchan)

/* Enable the channel. */
jz4780_dma_chn_writel(jzdma, jzchan->id, JZ_DMA_REG_DCS,
- JZ_DMA_DCS_DES8 | JZ_DMA_DCS_CTE);
+ JZ_DMA_DCS_CTE);
}

static void jz4780_dma_issue_pending(struct dma_chan *chan)
--
2.11.0
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