X-Git-Url: https://git.karo-electronics.de/?a=blobdiff_plain;f=drivers%2Fdma%2Fep93xx_dma.c;h=c64917ec313dc25d501ad41312fa8e898df8e003;hb=ce53044c68cf4fb6c50a2a0d88786be65fae7235;hp=f6e9b572b998919ee117cf154e560788da439de3;hpb=6133308ad1a386e7e7f776003a1c44e8b54e2166;p=linux-beck.git

diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index f6e9b572b998..c64917ec313d 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -71,6 +71,7 @@
 #define M2M_CONTROL_TM_SHIFT		13
 #define M2M_CONTROL_TM_TX		(1 << M2M_CONTROL_TM_SHIFT)
 #define M2M_CONTROL_TM_RX		(2 << M2M_CONTROL_TM_SHIFT)
+#define M2M_CONTROL_NFBINT		BIT(21)
 #define M2M_CONTROL_RSS_SHIFT		22
 #define M2M_CONTROL_RSS_SSPRX		(1 << M2M_CONTROL_RSS_SHIFT)
 #define M2M_CONTROL_RSS_SSPTX		(2 << M2M_CONTROL_RSS_SHIFT)
@@ -79,7 +80,22 @@
 #define M2M_CONTROL_PWSC_SHIFT		25
 
 #define M2M_INTERRUPT			0x0004
-#define M2M_INTERRUPT_DONEINT		BIT(1)
+#define M2M_INTERRUPT_MASK		6
+
+#define M2M_STATUS			0x000c
+#define M2M_STATUS_CTL_SHIFT		1
+#define M2M_STATUS_CTL_IDLE		(0 << M2M_STATUS_CTL_SHIFT)
+#define M2M_STATUS_CTL_STALL		(1 << M2M_STATUS_CTL_SHIFT)
+#define M2M_STATUS_CTL_MEMRD		(2 << M2M_STATUS_CTL_SHIFT)
+#define M2M_STATUS_CTL_MEMWR		(3 << M2M_STATUS_CTL_SHIFT)
+#define M2M_STATUS_CTL_BWCWAIT		(4 << M2M_STATUS_CTL_SHIFT)
+#define M2M_STATUS_CTL_MASK		(7 << M2M_STATUS_CTL_SHIFT)
+#define M2M_STATUS_BUF_SHIFT		4
+#define M2M_STATUS_BUF_NO		(0 << M2M_STATUS_BUF_SHIFT)
+#define M2M_STATUS_BUF_ON		(1 << M2M_STATUS_BUF_SHIFT)
+#define M2M_STATUS_BUF_NEXT		(2 << M2M_STATUS_BUF_SHIFT)
+#define M2M_STATUS_BUF_MASK		(3 << M2M_STATUS_BUF_SHIFT)
+#define M2M_STATUS_DONE			BIT(6)
 
 #define M2M_BCR0			0x0010
 #define M2M_BCR1			0x0014
@@ -426,15 +442,6 @@ static int m2p_hw_interrupt(struct ep93xx_dma_chan *edmac)
 
 /*
  * M2M DMA implementation
- *
- * For the M2M transfers we don't use NFB at all. This is because it simply
- * doesn't work well with memcpy transfers. When you submit both buffers it is
- * extremely unlikely that you get an NFB interrupt, but it instead reports
- * DONE interrupt and both buffers are already transferred which means that we
- * weren't able to update the next buffer.
- *
- * So for now we "simulate" NFB by just submitting buffer after buffer
- * without double buffering.
  */
 
 static int m2m_hw_setup(struct ep93xx_dma_chan *edmac)
@@ -543,6 +550,11 @@ static void m2m_hw_submit(struct ep93xx_dma_chan *edmac)
 	m2m_fill_desc(edmac);
 	control |= M2M_CONTROL_DONEINT;
 
+	if (ep93xx_dma_advance_active(edmac)) {
+		m2m_fill_desc(edmac);
+		control |= M2M_CONTROL_NFBINT;
+	}
+
 	/*
 	 * Now we can finally enable the channel. For M2M channel this must be
 	 * done _after_ the BCRx registers are programmed.
@@ -560,32 +572,89 @@ static void m2m_hw_submit(struct ep93xx_dma_chan *edmac)
 	}
 }
 
+/*
+ * According to EP93xx User's Guide, we should receive DONE interrupt when all
+ * M2M DMA controller transactions complete normally. This is not always the
+ * case - sometimes EP93xx M2M DMA asserts DONE interrupt when the DMA channel
+ * is still running (channel Buffer FSM in DMA_BUF_ON state, and channel
+ * Control FSM in DMA_MEM_RD state, observed at least in IDE-DMA operation).
+ * In effect, disabling the channel when only DONE bit is set could stop
+ * currently running DMA transfer. To avoid this, we use Buffer FSM and
+ * Control FSM to check current state of DMA channel.
+ */
 static int m2m_hw_interrupt(struct ep93xx_dma_chan *edmac)
 {
+	u32 status = readl(edmac->regs + M2M_STATUS);
+	u32 ctl_fsm = status & M2M_STATUS_CTL_MASK;
+	u32 buf_fsm = status & M2M_STATUS_BUF_MASK;
+	bool done = status & M2M_STATUS_DONE;
+	bool last_done;
 	u32 control;
+	struct ep93xx_dma_desc *desc;
 
-	if (!(readl(edmac->regs + M2M_INTERRUPT) & M2M_INTERRUPT_DONEINT))
+	/* Accept only DONE and NFB interrupts */
+	if (!(readl(edmac->regs + M2M_INTERRUPT) & M2M_INTERRUPT_MASK))
 		return INTERRUPT_UNKNOWN;
 
-	/* Clear the DONE bit */
-	writel(0, edmac->regs + M2M_INTERRUPT);
+	if (done) {
+		/* Clear the DONE bit */
+		writel(0, edmac->regs + M2M_INTERRUPT);
+	}
 
-	/* Disable interrupts and the channel */
-	control = readl(edmac->regs + M2M_CONTROL);
-	control &= ~(M2M_CONTROL_DONEINT | M2M_CONTROL_ENABLE);
-	writel(control, edmac->regs + M2M_CONTROL);
+	/*
+	 * Check whether we are done with descriptors or not. This, together
+	 * with DMA channel state, determines action to take in interrupt.
+	 */
+	desc = ep93xx_dma_get_active(edmac);
+	last_done = !desc || desc->txd.cookie;
 
 	/*
-	 * Since we only get DONE interrupt we have to find out ourselves
-	 * whether there still is something to process. So we try to advance
-	 * the chain an see whether it succeeds.
+	 * Use M2M DMA Buffer FSM and Control FSM to check current state of
+	 * DMA channel. Using DONE and NFB bits from channel status register
+	 * or bits from channel interrupt register is not reliable.
 	 */
-	if (ep93xx_dma_advance_active(edmac)) {
-		edmac->edma->hw_submit(edmac);
-		return INTERRUPT_NEXT_BUFFER;
+	if (!last_done &&
+	    (buf_fsm == M2M_STATUS_BUF_NO ||
+	     buf_fsm == M2M_STATUS_BUF_ON)) {
+		/*
+		 * Two buffers are ready for update when Buffer FSM is in
+		 * DMA_NO_BUF state. Only one buffer can be prepared without
+		 * disabling the channel or polling the DONE bit.
+		 * To simplify things, always prepare only one buffer.
+		 */
+		if (ep93xx_dma_advance_active(edmac)) {
+			m2m_fill_desc(edmac);
+			if (done && !edmac->chan.private) {
+				/* Software trigger for memcpy channel */
+				control = readl(edmac->regs + M2M_CONTROL);
+				control |= M2M_CONTROL_START;
+				writel(control, edmac->regs + M2M_CONTROL);
+			}
+			return INTERRUPT_NEXT_BUFFER;
+		} else {
+			last_done = true;
+		}
+	}
+
+	/*
+	 * Disable the channel only when Buffer FSM is in DMA_NO_BUF state
+	 * and Control FSM is in DMA_STALL state.
+	 */
+	if (last_done &&
+	    buf_fsm == M2M_STATUS_BUF_NO &&
+	    ctl_fsm == M2M_STATUS_CTL_STALL) {
+		/* Disable interrupts and the channel */
+		control = readl(edmac->regs + M2M_CONTROL);
+		control &= ~(M2M_CONTROL_DONEINT | M2M_CONTROL_NFBINT
+			    | M2M_CONTROL_ENABLE);
+		writel(control, edmac->regs + M2M_CONTROL);
+		return INTERRUPT_DONE;
 	}
 
-	return INTERRUPT_DONE;
+	/*
+	 * Nothing to do this time.
+	 */
+	return INTERRUPT_NEXT_BUFFER;
 }
 
 /*