From: Frank Mori Hess <fmhess@speakeasy.net>
Date: Fri, 22 Jun 2001 15:50:42 +0000 (+0000)
Subject: dma is no longer disabled in das1800 driver when rt suppport is configured
X-Git-Tag: r0_7_60~138
X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=3236df9cd914d187ae10ebd44dbd1268ad8fc6b4;p=comedi.git

dma is no longer disabled in das1800 driver when rt suppport is configured
for comedi.  dma is instead disabled on a cmd by cmd basis when the TRIG_RT
flag is received.
---

diff --git a/Documentation/comedi/drivers.txt b/Documentation/comedi/drivers.txt
index ec6dd1a8..8f22f213 100644
--- a/Documentation/comedi/drivers.txt
+++ b/Documentation/comedi/drivers.txt
@@ -333,8 +333,7 @@ Device Names: das-1701st, das-1701st-da, das-1701ao, das-1702st,
   das-1802hr, das-1802hr-da, das-1802hc, das-1802ao
 Status: works
 
-Presently, DMA is disabled if you enable hard real-time support for
-Comedi.  The waveform analog output on the 'ao' cards is not supported.
+The waveform analog output on the 'ao' cards is not supported.
 If you need it, send me (Frank Hess) an email.
 
 Configuration options:
diff --git a/comedi/drivers/das1800.c b/comedi/drivers/das1800.c
index a920c2b8..bbf456c7 100644
--- a/comedi/drivers/das1800.c
+++ b/comedi/drivers/das1800.c
@@ -69,8 +69,6 @@ at least 1 and no more than 0x10000 == 65536
 NOTES:
 Only the DAS-1801ST has been tested by me.
 Unipolar and bipolar ranges cannot be mixed in the channel/gain list.
-For safety reasons, the driver disables dma transfers if you enable
-	real-time support in comedi.
 
 TODO:
 	Add support for analog out on 'ao' cards.
@@ -498,21 +496,11 @@ static int das1800_attach(comedi_device *dev, comedi_devconfig *it)
 	unsigned long flags;
 	int iobase = it->options[0];
 	int irq = it->options[1];
-	int dma0, dma1;
+	int dma0 = it->options[2];
+	int dma1 = it->options[3];
 	int iobase2;
 	int board;
 
-// disable unsafe isa dma if comedi real time kernel support is on
-#ifdef CONFIG_COMEDI_RT
-	dma0 = 0;
-	dma1 = 0;
-	if(it->options[2] || it->options[3])
-		printk("%s: dma disabled to avoid conflicts with RT support\n", driver_das1800.driver_name);
-#else
-	dma0 = it->options[2];
-	dma1 = it->options[3];
-#endif
-
 	/* allocate and initialize dev->private */
 	if(alloc_private(dev, sizeof(das1800_private)) < 0)
 		return -ENOMEM;
@@ -1472,20 +1460,25 @@ static int das1800_ai_do_cmd(comedi_device *dev, comedi_subdevice *s)
 		return -1;
 	}
 
+	/* disable dma on TRIG_WAKE_EOS (to reduce latency) or TRIG_RT
+	 * (because dma in handler is unsafe at hard real-time priority) */
+	if(cmd.flags & (TRIG_WAKE_EOS | TRIG_RT))
+	{
+		devpriv->irq_dma_bits &= ~DMA_ENABLED;
+	}else
+	{
+		devpriv->irq_dma_bits |= devpriv->dma_bits;
+	}
+	// interrupt on end of conversion for TRIG_WAKE_EOS
 	if(cmd.flags & TRIG_WAKE_EOS)
 	{
 		// interrupt fifo not empty
 		devpriv->irq_dma_bits &= ~FIMD;
-		// turn off dma
-		devpriv->irq_dma_bits &= ~DMA_ENABLED;
 	}else
 	{
 		// interrupt fifo half full
 		devpriv->irq_dma_bits |= FIMD;
-		// turn on dma if configured
-		devpriv->irq_dma_bits |= devpriv->dma_bits;
 	}
-
 	// determine how many conversions we need
 	if(cmd.stop_src == TRIG_COUNT)
 	{