linux-kernel - [PATCH v2 03/11] dmaengine: dw: set polarity of handshake interface

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Date:	Mon, 11 Apr 2016 15:51:03 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Bryan O'Donoghue <pure.logic@...us-software.ie>,
	Peter Hurley <peter@...leysoftware.com>,
	linux-serial@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	ismo.puustinen@...el.com,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v2 03/11] dmaengine: dw: set polarity of handshake interface

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.shevchenko@...ux.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 f586ba1..57105ca 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -143,6 +143,8 @@ 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 06227d0..6196139 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;
 };
 
 /**
-- 
2.8.0.rc3