dmaengine: uniphier-xdmac: Add UniPhier external DMA controller driver

This adds external DMA controller driver implemented in Socionext
UniPhier SoCs. This driver supports DMA_MEMCPY and DMA_SLAVE modes.

Since this driver does not support the the way to transfer size
unaligned to burst width, 'src_maxburst' or 'dst_maxburst' of
dma_slave_config must be 1 to transfer arbitrary size. If transfer
size is unaligned to burst size, the transfer isn't started and
the driver displays an error message.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Link: https://lore.kernel.org/r/1582271550-3403-3-git-send-email-hayashi.kunihiko@socionext.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/Kconfig

@@ -658,6 +658,17 @@ config UNIPHIER_MDMAC
 	  UniPhier platform.  This DMA controller is used as the external
 	  DMA engine of the SD/eMMC controllers of the LD4, Pro4, sLD8 SoCs.
 
+config UNIPHIER_XDMAC
+	tristate "UniPhier XDMAC support"
+	depends on ARCH_UNIPHIER || COMPILE_TEST
+	depends on OF
+	select DMA_ENGINE
+	select DMA_VIRTUAL_CHANNELS
+	help
+	  Enable support for the XDMAC (external DMA controller) on the
+	  UniPhier platform. This DMA controller can transfer data from
+	  memory to memory, memory to peripheral and peripheral to memory.
+
 config XGENE_DMA
 	tristate "APM X-Gene DMA support"
 	depends on ARCH_XGENE || COMPILE_TEST

drivers/dma/Makefile

@@ -78,6 +78,7 @@ obj-$(CONFIG_TEGRA20_APB_DMA) += tegra20-apb-dma.o
 obj-$(CONFIG_TEGRA210_ADMA) += tegra210-adma.o
 obj-$(CONFIG_TIMB_DMA) += timb_dma.o
 obj-$(CONFIG_UNIPHIER_MDMAC) += uniphier-mdmac.o
+obj-$(CONFIG_UNIPHIER_XDMAC) += uniphier-xdmac.o
 obj-$(CONFIG_XGENE_DMA) += xgene-dma.o
 obj-$(CONFIG_ZX_DMA) += zx_dma.o
 obj-$(CONFIG_ST_FDMA) += st_fdma.o