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[v8,08/10] dmaengine: dw: Initialize min and max burst DMA device capability

Message ID 20200723005848.31907-9-Sergey.Semin@baikalelectronics.ru (mailing list archive)
State Accepted
Headers show
Series dmaengine: dw: Take Baikal-T1 SoC DW DMAC peculiarities into account | expand

Commit Message

Serge Semin July 23, 2020, 12:58 a.m. UTC 
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 <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

---

Changelog v4:
- This is a new patch suggested by Andy.

Changelog v5:
- Introduce macro with extreme min and max burst length supported by the
  DW DMA controller.
- Initialize max_burst length capability with extreme burst length supported
  by the DW DMAC IP-core.
---
 drivers/dma/dw/core.c                | 2 ++
 include/linux/platform_data/dma-dw.h | 2 ++
 2 files changed, 4 insertions(+)
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Patch

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index fb95920c429e..afe5a2e465af 100644
--- a/drivers/dma/dw/core.c
+++ b/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) |
diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h
index f3eaf9ec00a1..369e41e9dcc9 100644
--- a/include/linux/platform_data/dma-dw.h
+++ b/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