Messages in this thread | | | Date | Thu, 16 Jan 2014 11:30:48 +0000 | From | Ian Abbott <> | Subject | Re: [PATCH v7] Staging: comedi: convert while loop to timeout in ni_mio_common.c |
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On 2014-01-15 19:22, Chase Southwood wrote: > This patch for ni_mio_common.c changes out a while loop for a timeout, > which is preferred. > > Signed-off-by: Chase Southwood <chase.southwood@yahoo.com> > --- > > Hartley, > I sincerely apologize for the obvious mistake, I thought I had built it > but clearly I made a mistake somewhere, as your observation is exactly > correct. It is now fixed. > > Thanks, > Chase Southwood > > 2: Changed from simple clean-up to swapping a timeout in for a while loop. > > 3: Removed extra counter variable, and added error checking. > > 4: No longer using counter variable, using jiffies instead. > > 5: udelay for 10u, instead of 1u. > > 6: Scrap udelay entirely, in favor of cpu_relax. Include asm/processor.h > in order to use cpu_relax. > > 7: Fix typo (msec vs msecs). > > drivers/staging/comedi/drivers/ni_mio_common.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c > index 457b884..ab7a74c 100644 > --- a/drivers/staging/comedi/drivers/ni_mio_common.c > +++ b/drivers/staging/comedi/drivers/ni_mio_common.c > @@ -55,6 +55,7 @@ > #include <linux/interrupt.h> > #include <linux/sched.h> > #include <linux/delay.h> > +#include <asm/processor.h> > #include "8255.h" > #include "mite.h" > #include "comedi_fc.h" > @@ -687,12 +688,21 @@ static void ni_clear_ai_fifo(struct comedi_device *dev) > { > const struct ni_board_struct *board = comedi_board(dev); > struct ni_private *devpriv = dev->private; > + unsigned long timeout; > > if (board->reg_type == ni_reg_6143) { > /* Flush the 6143 data FIFO */ > ni_writel(0x10, AIFIFO_Control_6143); /* Flush fifo */ > ni_writel(0x00, AIFIFO_Control_6143); /* Flush fifo */ > - while (ni_readl(AIFIFO_Status_6143) & 0x10) ; /* Wait for complete */ > + /* Wait for complete */ > + timeout = jiffies + msecs_to_jiffies(500); > + while (ni_readl(AIFIFO_Status_6143) & 0x10) { > + if (time_after(jiffies, timeout)) { > + comedi_error(dev, "FIFO flush timeout."); > + break; > + } > + cpu_relax(); > + } > } else { > devpriv->stc_writew(dev, 1, ADC_FIFO_Clear); > if (board->reg_type == ni_reg_625x) { >
Sorry this is your worst nightmare, Chase. Your patch is great and has been modified in all the ways various people have suggested, but I don't think it is suitable.
After examining the code, it turns out ni_clear_ai_fifo() is sometimes called from an interrupt service routine and I don't think you can wait for jiffies to change in that case. I think we need to go back to your PATCH v2 and fix up the checkpatch.pl warning that Greg mentioned.
Sorry about that.
-- -=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@mev.co.uk> )=- -=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-
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