[PATCH v4 03/11] dmaengine: dw: set polarity of handshake interface

[Andy Shevchenko]

Intel Quark UART uses DesignWare DMA IP. Though the DMA IP is connected in such
way that handshake interface uses inverted polarity. We have to provide a
possibility to set this in the DMA driver when configuring a channel.

Introduce a new member of custom slave configuration called 'polarity' and set
active low polarity in case this value is 'true'.

Signed-off-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
---
 drivers/dma/dw/core.c                | 2 ++
 include/linux/platform_data/dma-dw.h | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 81b06df..9c7bc7a 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -150,6 +150,8 @@ static void dwc_initialize(struct dw_dma_chan *dwc)
        cfghi |= DWC_CFGH_DST_PER(dwc->dws.dst_id);
        cfghi |= DWC_CFGH_SRC_PER(dwc->dws.src_id);
 
+       cfglo |= dwc->dws.polarity ? DWC_CFGL_HS_DST_POL | DWC_CFGL_HS_SRC_POL 
: 0;
+
        channel_writel(dwc, CFG_LO, cfglo);
        channel_writel(dwc, CFG_HI, cfghi);
 
diff --git a/include/linux/platform_data/dma-dw.h 
b/include/linux/platform_data/dma-dw.h
index d15d8ba..192f3a2 100644
--- a/include/linux/platform_data/dma-dw.h
+++ b/include/linux/platform_data/dma-dw.h
@@ -23,6 +23,7 @@
  * @dst_id:    dst request line
  * @m_master:  memory master for transfers on allocated channel
  * @p_master:  peripheral master for transfers on allocated channel
+ * @polarity:  set active low polarity of handshake interface
  */
 struct dw_dma_slave {
        struct device           *dma_dev;
@@ -30,6 +31,7 @@ struct dw_dma_slave {
        u8                      dst_id;
        u8                      m_master;
        u8                      p_master;
+       bool                    polarity;
 };
 
 /**
-- 
2.8.1