[incubator-nuttx] branch master updated: arch: cxd56xx: Introduce CONFIG_CXD56_SPI_DMATHRESHOLD

[je...@apache.org]

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jerpelea pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/incubator-nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 52286f6  arch: cxd56xx: Introduce CONFIG_CXD56_SPI_DMATHRESHOLD
52286f6 is described below

commit 52286f6dec35728d8e055e20cc623c7bea13a164
Author: Masayuki Ishikawa <ma...@gmail.com>
AuthorDate: Mon Aug 24 16:52:25 2020 +0900

    arch: cxd56xx: Introduce CONFIG_CXD56_SPI_DMATHRESHOLD
    
    Summary:
    - This commit improves SPI performance.
    - For small data, it does not use DMA.
    
    Impact:
    - All use cases which use SPI with DMA
    
    Testing:
    - Tested with spresense:wifi and spresense:example_lcd
    
    Signed-off-by: Masayuki Ishikawa <Ma...@jp.sony.com>
---
 arch/arm/src/cxd56xx/Kconfig     | 9 +++++++++
 arch/arm/src/cxd56xx/cxd56_spi.c | 8 +++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm/src/cxd56xx/Kconfig b/arch/arm/src/cxd56xx/Kconfig
index 49839eb..62a0882 100644
--- a/arch/arm/src/cxd56xx/Kconfig
+++ b/arch/arm/src/cxd56xx/Kconfig
@@ -356,6 +356,15 @@ config CXD56_SPI_DRIVER
 		used to perform SPI bus transfers from applications.  The intent of
 		this driver is to support SPI testing.
 
+config CXD56_SPI_DMATHRESHOLD
+       int "SPI DMA threshold"
+       default 64
+       depends on CXD56_DMAC
+	---help---
+		When SPI DMA is enabled, small DMA transfers will still be performed
+		by polling logic.  But we need a threshold value to determine what
+		is small.
+
 config CXD56_SPI0
 	bool "SPI0"
 
diff --git a/arch/arm/src/cxd56xx/cxd56_spi.c b/arch/arm/src/cxd56xx/cxd56_spi.c
index 67c5fd5..b0d8ded 100644
--- a/arch/arm/src/cxd56xx/cxd56_spi.c
+++ b/arch/arm/src/cxd56xx/cxd56_spi.c
@@ -855,7 +855,13 @@ static void spi_exchange(FAR struct spi_dev_s *dev, FAR const void *txbuffer,
 #ifdef CONFIG_CXD56_DMAC
   FAR struct cxd56_spidev_s *priv = (FAR struct cxd56_spidev_s *)dev;
 
-  if (priv->dmaenable)
+#ifdef CONFIG_CXD56_SPI_DMATHRESHOLD
+  size_t dmath = CONFIG_CXD56_SPI_DMATHRESHOLD;
+#else
+  size_t dmath = 0;
+#endif
+
+  if (priv->dmaenable && dmath < nwords)
     {
       spi_dmaexchange(dev, txbuffer, rxbuffer, nwords);
     }