linux-kernel - Re: [PATCH 1/7 v2] dmaengine: add a simple dma library

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Date:	Fri, 27 Jan 2012 17:37:34 +0900
From:	"Shimoda, Yoshihiro" <yoshihiro.shimoda.uh@...esas.com>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org,
	Vinod Koul <vinod.koul@...el.com>,
	Magnus Damm <magnus.damm@...il.com>, linux-mmc@...r.kernel.org,
	alsa-devel@...a-project.org, linux-serial@...r.kernel.org,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH 1/7 v2] dmaengine: add a simple dma library

Hello Guennadi-san,

2012/01/26 23:56, Guennadi Liakhovetski wrote:
> This patch adds a library of functions, helping to implement dmaengine
> drivers for hardware, unable to handle scatter-gather lists natively.
> The first version of this driver only supports memcpy and slave DMA
> operation.
> 
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@....de>
> ---
> 
> v2:
> 
> 1. switch from using a tasklet to threaded IRQ, which allowed to

I tested this driver on 2 environment, but it could not work correctly.
 - renesas_usbhs driver with shdma driver on the mackerel board
 - renesas_usbhs driver with experimental SUDMAC driver

In this case, should we modify the renesas_usbhs driver?
For reference, if I changed the threaded IRQ to tasklet,
the 2 environment worked correctly:
==============
diff --git a/drivers/dma/dma-simple.c b/drivers/dma/dma-simple.c
index 49d8f7d..65a5170 100644
--- a/drivers/dma/dma-simple.c
+++ b/drivers/dma/dma-simple.c
@@ -715,16 +715,18 @@ static irqreturn_t chan_irq(int irq, void *dev)

 	spin_lock(&schan->chan_lock);

-	ret = ops->chan_irq(schan, irq) ? IRQ_WAKE_THREAD : IRQ_NONE;
+	ret = ops->chan_irq(schan, irq) ? IRQ_HANDLED : IRQ_NONE;
+	if (ret == IRQ_HANDLED)
+		tasklet_schedule(&schan->tasklet);

 	spin_unlock(&schan->chan_lock);

 	return ret;
 }

-static irqreturn_t chan_irqt(int irq, void *dev)
+static void chan_irqt(unsigned long dev)
 {
-	struct dma_simple_chan *schan = dev;
+	struct dma_simple_chan *schan = (struct dma_simple_chan *)dev;
 	const struct dma_simple_ops *ops =
 		to_simple_dev(schan->dma_chan.device)->ops;
 	struct dma_simple_desc *sdesc;
@@ -744,15 +746,13 @@ static irqreturn_t chan_irqt(int irq, void *dev)
 	spin_unlock_irq(&schan->chan_lock);

 	simple_chan_ld_cleanup(schan, false);
-
-	return IRQ_HANDLED;
 }

 int dma_simple_request_irq(struct dma_simple_chan *schan, int irq,
 			   unsigned long flags, const char *name)
 {
-	int ret = request_threaded_irq(irq, chan_irq, chan_irqt,
-				       flags, name, schan);
+	int ret = request_irq(irq, chan_irq, flags, name, schan);
+	tasklet_init(&schan->tasklet, chan_irqt, (unsigned long)schan);

 	schan->irq = ret < 0 ? ret : irq;

diff --git a/include/linux/dma-simple.h b/include/linux/dma-simple.h
index 5336674..beb1489 100644
--- a/include/linux/dma-simple.h
+++ b/include/linux/dma-simple.h
@@ -68,6 +68,7 @@ struct dma_simple_chan {
 	int id;				/* Raw id of this channel */
 	int irq;			/* Channel IRQ */
 	enum dma_simple_pm_state pm_state;
+	struct tasklet_struct tasklet;
 };

 /**
==============

Best regards,
Yoshihiro Shimoda
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