linux-kernel - [PATCH v3 3/3] dmaengine: at_xdmac: only monitor overflow errors for peripheral xfer

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Date:   Wed, 3 Apr 2019 12:23:59 +0200
From:   Nicolas Ferre <nicolas.ferre@...rochip.com>
To:     <dmaengine@...r.kernel.org>, Vinod Koul <vkoul@...nel.org>
CC:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        <linux-kernel@...r.kernel.org>,
        "Nicolas Ferre" <nicolas.ferre@...rochip.com>
Subject: [PATCH v3 3/3] dmaengine: at_xdmac: only monitor overflow errors for peripheral xfer

The overflow error flag (ROI: Request Overflow Error) is only relevant
for the case when the channel handles a peripheral synchronized transfer.
Not in the case of memory to memory transfer where there is no hardware
request signal.

Remove the use of this interrupt source in such a case. It's based on
the first descriptor which holds the configuration for the whole
linked list transfer.

Signed-off-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
---
v3: no change
v2: added Ludovic's tag

 drivers/dma/at_xdmac.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 1dd7edaefbdc..06cbe54e4c30 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -308,6 +308,11 @@ static inline int at_xdmac_csize(u32 maxburst)
 	return csize;
 };
 
+static inline bool at_xdmac_chan_is_peripheral_xfer(u32 cfg)
+{
+	return cfg & AT_XDMAC_CC_TYPE_PER_TRAN;
+}
+
 static inline u8 at_xdmac_get_dwidth(u32 cfg)
 {
 	return (cfg & AT_XDMAC_CC_DWIDTH_MASK) >> AT_XDMAC_CC_DWIDTH_OFFSET;
@@ -389,7 +394,13 @@ static void at_xdmac_start_xfer(struct at_xdmac_chan *atchan,
 		 at_xdmac_chan_read(atchan, AT_XDMAC_CUBC));
 
 	at_xdmac_chan_write(atchan, AT_XDMAC_CID, 0xffffffff);
-	reg = AT_XDMAC_CIE_RBEIE | AT_XDMAC_CIE_WBEIE | AT_XDMAC_CIE_ROIE;
+	reg = AT_XDMAC_CIE_RBEIE | AT_XDMAC_CIE_WBEIE;
+	/*
+	 * Request Overflow Error is only for peripheral synchronized transfers
+	 */
+	if (at_xdmac_chan_is_peripheral_xfer(first->lld.mbr_cfg))
+		reg |= AT_XDMAC_CIE_ROIE;
+
 	/*
 	 * There is no end of list when doing cyclic dma, we need to get
 	 * an interrupt after each periods.
-- 
2.17.1