Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752388AbaAPLa5 (ORCPT ); Thu, 16 Jan 2014 06:30:57 -0500 Received: from mail.mev.co.uk ([62.49.15.74]:53550 "EHLO mail.mev.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751535AbaAPLax (ORCPT ); Thu, 16 Jan 2014 06:30:53 -0500 Message-ID: <52D7C2E8.9060204@mev.co.uk> Date: Thu, 16 Jan 2014 11:30:48 +0000 From: Ian Abbott User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Chase Southwood , "gregkh@linuxfoundation.org" CC: Ian Abbott , "hsweeten@visionengravers.com" , "devel@driverdev.osuosl.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v7] Staging: comedi: convert while loop to timeout in ni_mio_common.c References: <1389669228-15090-1-git-send-email-chase.southwood@yahoo.com> <1389813752-3009-1-git-send-email-chase.southwood@yahoo.com> In-Reply-To: <1389813752-3009-1-git-send-email-chase.southwood@yahoo.com> Content-Type: text/plain; charset="us-ascii"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > > 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 > #include > #include > +#include > #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: )=- -=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/