Adds the function ipu_idmac_enable_watermark(), which enables or disables
watermarking in the IDMAC channel. Enabling watermarking can increase a
channel's AXI bus arbitration priority.

Signed-off-by: Steve Longerbeam <steve_longerb...@mentor.com>
---
 drivers/staging/imx-drm/ipu-v3/ipu-common.c |   25 +++++++++++++++++++++++++
 include/linux/platform_data/imx-ipu-v3.h    |    1 +
 2 files changed, 26 insertions(+)

diff --git a/drivers/staging/imx-drm/ipu-v3/ipu-common.c 
b/drivers/staging/imx-drm/ipu-v3/ipu-common.c
index 32a51d6..8c5b8d3 100644
--- a/drivers/staging/imx-drm/ipu-v3/ipu-common.c
+++ b/drivers/staging/imx-drm/ipu-v3/ipu-common.c
@@ -982,6 +982,31 @@ int ipu_idmac_disable_channel(struct ipuv3_channel 
*channel)
 }
 EXPORT_SYMBOL_GPL(ipu_idmac_disable_channel);
 
+/*
+ * The imx6 rev. D TRM says that enabling the WM feature will increase
+ * a channel's priority. Refer to Table 36-8 Calculated priority value.
+ * The sub-module that is the sink or source for the channel must enable
+ * watermark signal for this to take effect (SMFC_WM for instance).
+ */
+void ipu_idmac_enable_watermark(struct ipuv3_channel *channel, bool enable)
+{
+       struct ipu_soc *ipu = channel->ipu;
+       unsigned long flags;
+       u32 val;
+
+       spin_lock_irqsave(&ipu->lock, flags);
+
+       val = ipu_idmac_read(ipu, IDMAC_WM_EN(channel->num));
+       if (enable)
+               val |= 1 << (channel->num % 32);
+       else
+               val &= ~(1 << (channel->num % 32));
+       ipu_idmac_write(ipu, val, IDMAC_WM_EN(channel->num));
+
+       spin_unlock_irqrestore(&ipu->lock, flags);
+}
+EXPORT_SYMBOL_GPL(ipu_idmac_enable_watermark);
+
 static int ipu_memory_reset(struct ipu_soc *ipu)
 {
        unsigned long timeout;
diff --git a/include/linux/platform_data/imx-ipu-v3.h 
b/include/linux/platform_data/imx-ipu-v3.h
index 681b9fd..d1def4d 100644
--- a/include/linux/platform_data/imx-ipu-v3.h
+++ b/include/linux/platform_data/imx-ipu-v3.h
@@ -202,6 +202,7 @@ void ipu_idmac_select_buffer(struct ipuv3_channel *channel, 
u32 buf_num);
 void ipu_idmac_clear_buffer(struct ipuv3_channel *channel, u32 buf_num);
 bool ipu_idmac_buffer_is_ready(struct ipuv3_channel *channel, u32 buf_num);
 int ipu_idmac_current_buffer(struct ipuv3_channel *channel);
+void ipu_idmac_enable_watermark(struct ipuv3_channel *channel, bool enable);
 
 /*
  * IPU Display Controller (dc) functions
-- 
1.7.9.5

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