linux-kernel - Re: [PATCH v2 1/5] dmaengine: add ep93xx DMA support

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Message-ID: <20111121080158.GA2713@mwesterb-mobl.ger.corp.intel.com>
Date:	Mon, 21 Nov 2011 10:01:58 +0200
From:	Mika Westerberg <mika.westerberg@....fi>
To:	Rafal Prylowski <prylowski@...asoft.pl>
Cc:	linux-arm-kernel@...ts.infradead.org, rmallon@...il.com,
	vinod.koul@...el.com, broonie@...nsource.wolfsonmicro.com,
	linux-kernel@...r.kernel.org, grant.likely@...retlab.ca,
	hsweeten@...ionengravers.com, dan.j.williams@...el.com, lrg@...com
Subject: Re: [PATCH v2 1/5] dmaengine: add ep93xx DMA support

On Mon, Nov 21, 2011 at 08:44:07AM +0100, Rafal Prylowski wrote:
> 
> I'm calling dma_terminate_all from interrupt. It seems that tasklet_kill is not
> allowed to be called from this context.

Ah, right.

One more try - this time we set a flag which prevents the tasktlet from
referencing an empty list.

diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index 6181811..f7244b3 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -155,6 +155,8 @@ struct ep93xx_dma_chan {
 	unsigned long			flags;
 /* Channel is configured for cyclic transfers */
 #define EP93XX_DMA_IS_CYCLIC		0
+/* Channel is enabled */
+#define EP93xx_DMA_IS_RUNNING		1
 
 	int				buffer;
 	dma_cookie_t			last_completed;
@@ -673,6 +675,9 @@ static void ep93xx_dma_tasklet(unsigned long data)
 	void *callback_param;
 	LIST_HEAD(list);
 
+	if (!test_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags))
+		return;
+
 	spin_lock_irq(&edmac->lock);
 	desc = ep93xx_dma_get_active(edmac);
 	if (desc->complete) {
@@ -758,6 +763,8 @@ static dma_cookie_t ep93xx_dma_tx_submit(struct dma_async_tx_descriptor *tx)
 	edmac->chan.cookie = cookie;
 	desc->txd.cookie = cookie;
 
+	set_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags);
+
 	/*
 	 * If nothing is currently prosessed, we push this descriptor
 	 * directly to the hardware. Otherwise we put the descriptor
@@ -1106,6 +1113,7 @@ static int ep93xx_dma_terminate_all(struct ep93xx_dma_chan *edmac)
 	spin_lock_irqsave(&edmac->lock, flags);
 	/* First we disable and flush the DMA channel */
 	edmac->edma->hw_shutdown(edmac);
+	clear_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags);
 	clear_bit(EP93XX_DMA_IS_CYCLIC, &edmac->flags);
 	list_splice_init(&edmac->active, &list);
 	list_splice_init(&edmac->queue, &list);
--
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