From b609a5959f5ee44342d08ad37faba11bfbeb8b92 Mon Sep 17 00:00:00 2001
From: H Hartley Sweeten <hsweeten@visionengravers.com>
Date: Wed, 18 Sep 2013 11:48:41 -0700
Subject: [PATCH] staging: comedi: adl_pci6208: don't deadlock while waiting to
write ao data
Remove a possible deadlock while waiting to write the analog output data.
The data transfer rate for every D/A data write in this driver is 2.2us.
Wait up to 10us for the board to be ready then and return -ETIME.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/staging/comedi/drivers/adl_pci6208.c | 25 ++++++++++++++++----
1 file changed, 21 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/comedi/drivers/adl_pci6208.c b/drivers/staging/comedi/drivers/adl_pci6208.c
index 9150582fad068..059d7ea9503d1 100644
--- a/drivers/staging/comedi/drivers/adl_pci6208.c
+++ b/drivers/staging/comedi/drivers/adl_pci6208.c
@@ -39,6 +39,7 @@ References:
*/
#include <linux/module.h>
+#include <linux/delay.h>
#include <linux/pci.h>
#include "../comedidev.h"
@@ -82,6 +83,21 @@ struct pci6208_private {
unsigned int ao_readback[PCI6208_MAX_AO_CHANNELS];
};
+static int pci6208_ao_wait_for_data_send(struct comedi_device *dev,
+ unsigned int timeout)
+{
+ unsigned int status;
+
+ while (timeout--) {
+ status = inw(dev->iobase + PCI6208_AO_STATUS);
+ if ((status & PCI6208_AO_STATUS_DATA_SEND) == 0)
+ return 0;
+ udelay(1);
+ }
+
+ return -ETIME;
+}
+
static int pci6208_ao_winsn(struct comedi_device *dev,
struct comedi_subdevice *s,
struct comedi_insn *insn, unsigned int *data)
@@ -90,15 +106,16 @@ static int pci6208_ao_winsn(struct comedi_device *dev,
int chan = CR_CHAN(insn->chanspec);
unsigned int invert = 1 << (16 - 1);
unsigned int val = devpriv->ao_readback[chan];
- unsigned short status;
+ int ret;
int i;
for (i = 0; i < insn->n; i++) {
val = data[i];
- do {
- status = inw(dev->iobase + PCI6208_AO_STATUS);
- } while (status & PCI6208_AO_STATUS_DATA_SEND);
+ /* D/A transfer rate is 2.2us, wait up to 10us */
+ ret = pci6208_ao_wait_for_data_send(dev, 10);
+ if (ret)
+ return ret;
outw(val ^ invert, dev->iobase + PCI6208_AO_CONTROL(chan));
}
--
2.30.2