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Subject[PATCH v3 07/10] dmaengine: dw: Set DMA device max segment size parameter
Date
Maximum block size DW DMAC configuration corresponds to the max segment
size DMA parameter in the DMA core subsystem notation. Lets set it with a
value specific to the probed DW DMA controller. It shall help the DMA
clients to create size-optimized SG-list items for the controller. This in
turn will cause less dw_desc allocations, less LLP reinitializations,
better DMA device performance.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org

---

Changelog v2:
- This is a new patch created in place of the dropped one:
"dmaengine: dw: Add LLP and block size config accessors".

Changelog v3:
- Use the block_size found for the very first channel instead of looking for
the maximum of maximum block sizes.
- Don't define device-specific device_dma_parameters object, since it has
already been defined by the platform device core.
---
drivers/dma/dw/core.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 33e99d95b3d3..fb95920c429e 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -1229,6 +1229,13 @@ int do_dma_probe(struct dw_dma_chip *chip)
BIT(DMA_MEM_TO_MEM);
dw->dma.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;

+ /*
+ * For now there is no hardware with non uniform maximum block size
+ * across all of the device channels, so we set the maximum segment
+ * size as the block size found for the very first channel.
+ */
+ dma_set_max_seg_size(dw->dma.dev, dw->chan[0].block_size);
+
err = dma_async_device_register(&dw->dma);
if (err)
goto err_dma_register;
--
2.26.2
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