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misc: rp1-pio: Get burst size from DMA capabilities

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Although the PIO throughput benefits from larger burst sizes, only the
first two DMA channels support a burst size of 8 - the others are capped
at 4. To avoid misconfiguring the PIO hardware, retrieve the actual
max_burst value from the DMA channel's capabilities.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
This commit is contained in:
Phil Elwell
2025-10-14 09:16:46 +01:00
committed by Dom Cobley
parent a7ee0de997
commit 17db3d7b03
1 changed files with 5 additions and 2 deletions
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7
drivers/misc/rp1-pio.c
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@@ -611,6 +611,7 @@ static int rp1_pio_sm_config_xfer_internal(struct rp1_pio_client *client, uint s
struct platform_device *pdev = pio->pdev; struct platform_device *pdev = pio->pdev;
struct device *dev = &pdev->dev; struct device *dev = &pdev->dev;
struct dma_slave_config config = {}; struct dma_slave_config config = {};
struct dma_slave_caps dma_caps;
phys_addr_t fifo_addr; phys_addr_t fifo_addr;
struct dma_info *dma; struct dma_info *dma;
uint32_t dma_mask; uint32_t dma_mask;
@@ -676,10 +677,12 @@ static int rp1_pio_sm_config_xfer_internal(struct rp1_pio_client *client, uint s
config.src_addr = fifo_addr; config.src_addr = fifo_addr;
config.dst_addr = fifo_addr; config.dst_addr = fifo_addr;
config.direction = (dir == RP1_PIO_DIR_TO_SM) ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM; config.direction = (dir == RP1_PIO_DIR_TO_SM) ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM;
dma_caps.max_burst = 4;
dma_get_slave_caps(dma->chan, &dma_caps);
if (dir == RP1_PIO_DIR_TO_SM) if (dir == RP1_PIO_DIR_TO_SM)
config.dst_maxburst = 8; config.dst_maxburst = dma_caps.max_burst;
else else
config.src_maxburst = 8; config.src_maxburst = dma_caps.max_burst;
ret = dmaengine_slave_config(dma->chan, &config); ret = dmaengine_slave_config(dma->chan, &config);
if (ret) if (ret)