linux-kernel - [PATCH v2] dmaengine: at_xdmac: Fix wrongfull report of a channel as in use

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Message-ID: <20190123163339.17506-1-codrin.ciubotariu@microchip.com>
Date:   Wed, 23 Jan 2019 16:33:47 +0000
From:   <Codrin.Ciubotariu@...rochip.com>
To:     <Ludovic.Desroches@...rochip.com>, <vkoul@...nel.org>
CC:     <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Codrin.Ciubotariu@...rochip.com>
Subject: [PATCH v2] dmaengine: at_xdmac: Fix wrongfull report of a channel as
 in use

From: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>

atchan->status variable is used to store two different information:
 - pass channel interrupts status from interrupt handler to tasklet;
 - channel information like whether it is cyclic or paused;

This causes a bug when device_terminate_all() is called,
(AT_XDMAC_CHAN_IS_CYCLIC cleared on atchan->status) and then a late End
of Block interrupt arrives (AT_XDMAC_CIS_BIS), which sets bit 0 of
atchan->status. Bit 0 is also used for AT_XDMAC_CHAN_IS_CYCLIC, so when
a new descriptor for a cyclic transfer is created, the driver reports
the channel as in use:

if (test_and_set_bit(AT_XDMAC_CHAN_IS_CYCLIC, &atchan->status)) {
	dev_err(chan2dev(chan), "channel currently used\n");
	return NULL;
}

This patch fixes the bug by adding a different struct member to keep
the interrupts status separated from the channel status bits.

Fixes: e1f7c9eee707 ("dmaengine: at_xdmac: creation of the atmel eXtended DMA Controller driver")
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
---
 drivers/dma/at_xdmac.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 4e557684f792..fe69dccfa0c0 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -203,6 +203,7 @@ struct at_xdmac_chan {
 	u32				save_cim;
 	u32				save_cnda;
 	u32				save_cndc;
+	u32				irq_status;
 	unsigned long			status;
 	struct tasklet_struct		tasklet;
 	struct dma_slave_config		sconfig;
@@ -1580,8 +1581,8 @@ static void at_xdmac_tasklet(unsigned long data)
 	struct at_xdmac_desc	*desc;
 	u32			error_mask;
 
-	dev_dbg(chan2dev(&atchan->chan), "%s: status=0x%08lx\n",
-		 __func__, atchan->status);
+	dev_dbg(chan2dev(&atchan->chan), "%s: status=0x%08x\n",
+		__func__, atchan->irq_status);
 
 	error_mask = AT_XDMAC_CIS_RBEIS
 		     | AT_XDMAC_CIS_WBEIS
@@ -1589,15 +1590,15 @@ static void at_xdmac_tasklet(unsigned long data)
 
 	if (at_xdmac_chan_is_cyclic(atchan)) {
 		at_xdmac_handle_cyclic(atchan);
-	} else if ((atchan->status & AT_XDMAC_CIS_LIS)
-		   || (atchan->status & error_mask)) {
+	} else if ((atchan->irq_status & AT_XDMAC_CIS_LIS)
+		   || (atchan->irq_status & error_mask)) {
 		struct dma_async_tx_descriptor  *txd;
 
-		if (atchan->status & AT_XDMAC_CIS_RBEIS)
+		if (atchan->irq_status & AT_XDMAC_CIS_RBEIS)
 			dev_err(chan2dev(&atchan->chan), "read bus error!!!");
-		if (atchan->status & AT_XDMAC_CIS_WBEIS)
+		if (atchan->irq_status & AT_XDMAC_CIS_WBEIS)
 			dev_err(chan2dev(&atchan->chan), "write bus error!!!");
-		if (atchan->status & AT_XDMAC_CIS_ROIS)
+		if (atchan->irq_status & AT_XDMAC_CIS_ROIS)
 			dev_err(chan2dev(&atchan->chan), "request overflow error!!!");
 
 		spin_lock(&atchan->lock);
@@ -1652,7 +1653,7 @@ static irqreturn_t at_xdmac_interrupt(int irq, void *dev_id)
 			atchan = &atxdmac->chan[i];
 			chan_imr = at_xdmac_chan_read(atchan, AT_XDMAC_CIM);
 			chan_status = at_xdmac_chan_read(atchan, AT_XDMAC_CIS);
-			atchan->status = chan_status & chan_imr;
+			atchan->irq_status = chan_status & chan_imr;
 			dev_vdbg(atxdmac->dma.dev,
 				 "%s: chan%d: imr=0x%x, status=0x%x\n",
 				 __func__, i, chan_imr, chan_status);
@@ -1666,7 +1667,7 @@ static irqreturn_t at_xdmac_interrupt(int irq, void *dev_id)
 				 at_xdmac_chan_read(atchan, AT_XDMAC_CDA),
 				 at_xdmac_chan_read(atchan, AT_XDMAC_CUBC));
 
-			if (atchan->status & (AT_XDMAC_CIS_RBEIS | AT_XDMAC_CIS_WBEIS))
+			if (atchan->irq_status & (AT_XDMAC_CIS_RBEIS | AT_XDMAC_CIS_WBEIS))
 				at_xdmac_write(atxdmac, AT_XDMAC_GD, atchan->mask);
 
 			tasklet_schedule(&atchan->tasklet);
-- 
2.17.1