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Subject[PATCH v5 4/7] dmaengine: xilinx_dma: program hardware supported buffer length
Date
From: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>

AXI-DMA IP supports configurable (c_sg_length_width) buffer length
register width, hence read buffer length (xlnx,sg-length-width) DT
property and ensure that driver doesn't program buffer length
exceeding the supported limit. For VDMA and CDMA there is no change.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Andrea Merello <andrea.merello@gmail.com> [rebase, reword]
---
Changes in v2:
- drop original patch and replace with the one in Xilinx tree
Changes in v3:
- cc DT maintainers/ML
Changes in v4:
- upper bound for the property should be 26, not 23
- add warn for width > 23 as per xilinx original patch
- rework due to changes introduced in 1/6
Changes in v5:
None
---
drivers/dma/xilinx/xilinx_dma.c | 36 +++++++++++++++++++++++++--------
1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index aaa6de8a70e4..b17f24e4ec35 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -158,7 +158,9 @@
#define XILINX_DMA_REG_BTT 0x28

/* AXI DMA Specific Masks/Bit fields */
-#define XILINX_DMA_MAX_TRANS_LEN GENMASK(22, 0)
+#define XILINX_DMA_MAX_TRANS_LEN_MIN 8
+#define XILINX_DMA_MAX_TRANS_LEN_MAX 23
+#define XILINX_DMA_V2_MAX_TRANS_LEN_MAX 26
#define XILINX_DMA_CR_COALESCE_MAX GENMASK(23, 16)
#define XILINX_DMA_CR_CYCLIC_BD_EN_MASK BIT(4)
#define XILINX_DMA_CR_COALESCE_SHIFT 16
@@ -418,6 +420,7 @@ struct xilinx_dma_config {
* @rxs_clk: DMA s2mm stream clock
* @nr_channels: Number of channels DMA device supports
* @chan_id: DMA channel identifier
+ * @max_buffer_len: Max buffer length
*/
struct xilinx_dma_device {
void __iomem *regs;
@@ -437,6 +440,7 @@ struct xilinx_dma_device {
struct clk *rxs_clk;
u32 nr_channels;
u32 chan_id;
+ u32 max_buffer_len;
};

/* Macros */
@@ -964,7 +968,7 @@ static int xilinx_dma_calc_copysize(struct xilinx_dma_chan *chan,
int size, int done)
{
size_t copy = min_t(size_t, size - done,
- XILINX_DMA_MAX_TRANS_LEN);
+ chan->xdev->max_buffer_len);

if ((copy + done < size) &&
chan->xdev->common.copy_align) {
@@ -1011,7 +1015,7 @@ static enum dma_status xilinx_dma_tx_status(struct dma_chan *dchan,
list_for_each_entry(segment, &desc->segments, node) {
hw = &segment->hw;
residue += (hw->control - hw->status) &
- XILINX_DMA_MAX_TRANS_LEN;
+ chan->xdev->max_buffer_len;
}
}
spin_unlock_irqrestore(&chan->lock, flags);
@@ -1263,7 +1267,7 @@ static void xilinx_cdma_start_transfer(struct xilinx_dma_chan *chan)

/* Start the transfer */
dma_ctrl_write(chan, XILINX_DMA_REG_BTT,
- hw->control & XILINX_DMA_MAX_TRANS_LEN);
+ hw->control & chan->xdev->max_buffer_len);
}

list_splice_tail_init(&chan->pending_list, &chan->active_list);
@@ -1366,7 +1370,7 @@ static void xilinx_dma_start_transfer(struct xilinx_dma_chan *chan)

/* Start the transfer */
dma_ctrl_write(chan, XILINX_DMA_REG_BTT,
- hw->control & XILINX_DMA_MAX_TRANS_LEN);
+ hw->control & chan->xdev->max_buffer_len);
}

list_splice_tail_init(&chan->pending_list, &chan->active_list);
@@ -1727,7 +1731,7 @@ xilinx_cdma_prep_memcpy(struct dma_chan *dchan, dma_addr_t dma_dst,
struct xilinx_cdma_tx_segment *segment;
struct xilinx_cdma_desc_hw *hw;

- if (!len || len > XILINX_DMA_MAX_TRANS_LEN)
+ if (!len || len > chan->xdev->max_buffer_len)
return NULL;

desc = xilinx_dma_alloc_tx_descriptor(chan);
@@ -2596,7 +2600,7 @@ static int xilinx_dma_probe(struct platform_device *pdev)
struct xilinx_dma_device *xdev;
struct device_node *child, *np = pdev->dev.of_node;
struct resource *io;
- u32 num_frames, addr_width;
+ u32 num_frames, addr_width, len_width;
int i, err;

/* Allocate and initialize the DMA engine structure */
@@ -2628,8 +2632,24 @@ static int xilinx_dma_probe(struct platform_device *pdev)

/* Retrieve the DMA engine properties from the device tree */
xdev->has_sg = of_property_read_bool(node, "xlnx,include-sg");
- if (xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA)
+ xdev->max_buffer_len = GENMASK(XILINX_DMA_MAX_TRANS_LEN_MAX - 1, 0);
+
+ if (xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
xdev->mcdma = of_property_read_bool(node, "xlnx,mcdma");
+ if (!of_property_read_u32(node, "xlnx,sg-length-width",
+ &len_width)) {
+ if (len_width < XILINX_DMA_MAX_TRANS_LEN_MIN ||
+ len_width > XILINX_DMA_V2_MAX_TRANS_LEN_MAX) {
+ dev_warn(xdev->dev,
+ "invalid xlnx,sg-length-width property value. Using default width\n");
+ } else {
+ if (len_width > XILINX_DMA_MAX_TRANS_LEN_MAX)
+ dev_warn(xdev->dev, "Please ensure that IP supports buffer length > 23 bits\n");
+ xdev->max_buffer_len =
+ GENMASK(len_width - 1, 0);
+ }
+ }
+ }

if (xdev->dma_config->dmatype == XDMA_TYPE_VDMA) {
err = of_property_read_u32(node, "xlnx,num-fstores",
--
2.17.1
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