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staging: comedi: adl_pci6208: don't deadlock while waiting to write ao data

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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>
This commit is contained in:
H Hartley Sweeten 2013-09-18 11:48:41 -07:00 committed by Greg Kroah-Hartman
parent 20fb170b29
commit b609a5959f
1 changed files with 21 additions and 4 deletions
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25
drivers/staging/comedi/drivers/adl_pci6208.c
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@ -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));
}