dmaengine: dw: Initialize min and max burst DMA device capability

According to the DW APB DMAC data book the minimum burst transaction
length is 1 and it's true for any version of the controller since
isn't parametrised in the coreAssembler so can't be changed at the
IP-core synthesis stage. The maximum burst transaction can vary from
channel to channel and from controller to controller depending on a
IP-core parameter the system engineer activated during the IP-core
synthesis. Let's initialise both min_burst and max_burst members of the
DMA controller descriptor with extreme values so the DMA clients could
use them to properly optimize the DMA requests. The channels and
controller-specific max_burst length initialization will be introduced
by the follow-up patches.

Signed-off-by: Serge Semin <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: fancer

drivers/dma/dw/core.c

@@ -1223,6 +1223,8 @@ int do_dma_probe(struct dw_dma_chip *chip)
 	dw->dma.device_issue_pending = dwc_issue_pending;
 
 	/* DMA capabilities */
+	dw->dma.min_burst = DW_DMA_MIN_BURST;
+	dw->dma.max_burst = DW_DMA_MAX_BURST;
 	dw->dma.src_addr_widths = DW_DMA_BUSWIDTHS;
 	dw->dma.dst_addr_widths = DW_DMA_BUSWIDTHS;
 	dw->dma.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV) |

include/linux/platform_data/dma-dw.h

@@ -12,6 +12,8 @@
 
 #define DW_DMA_MAX_NR_MASTERS	4
 #define DW_DMA_MAX_NR_CHANNELS	8
+#define DW_DMA_MIN_BURST	1
+#define DW_DMA_MAX_BURST	256
 
 /**
  * struct dw_dma_slave - Controller-specific information about a slave