linux-kernel - Re: [PATCH 1/3] mtd: sh_flctl: fixup wait_for_completion

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Message-ID: <20150502064917.GA17454@opentech.at>
Date:	Sat, 2 May 2015 08:49:18 +0200
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Arnd Bergmann <arnd@...db.de>, linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mtd: sh_flctl: fixup wait_for_completion_timeout
	return handling

On Sat, 02 May 2015, Laurent Pinchart wrote:

> Hi Nicholas,
> 
> Thank you for the patch.
> 
> On Friday 01 May 2015 16:16:01 Nicholas Mc Guire wrote:
> > wait_for_completion_timeout() returns unsigned long not int so the check
> > for <= should be == and the type unsigned long. This fixes up the return
> > value handling and returns -ETIMEDOUT on timeout rather than 0 and 1 on
> > on success rather than a more or less random remaining number of jiffies.
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> > ---
> > 
> > call sites:
> > read_fiforeg,write_ec_fiforeg assume > 0 == success
> > and the comment in flctl_dma_fifo0_transfe states
> >         /* ret > 0 is success */
> >         return ret;
> > since it is only checking for > 0 in the call-sites
> > returning -ETIMEDOUT should be fine.
> > 
> > Patch was compile tested with ap325rxa_defconfig (implies
> > CONFIG_MTD_NAND_SH_FLCTL=y)
> > 
> > Patch is against 4.1-rc1 (localversion-next is -next-20150501)
> > 
> >  drivers/mtd/nand/sh_flctl.c |    9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/sh_flctl.c b/drivers/mtd/nand/sh_flctl.c
> > index c3ce81c..4450864 100644
> > --- a/drivers/mtd/nand/sh_flctl.c
> > +++ b/drivers/mtd/nand/sh_flctl.c
> > @@ -354,6 +354,7 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl
> > *flctl, unsigned long *buf, dma_cookie_t cookie = -EINVAL;
> >  	uint32_t reg;
> >  	int ret;
> > +	unsigned long time_left;
> > 
> >  	if (dir == DMA_FROM_DEVICE) {
> >  		chan = flctl->chan_fifo0_rx;
> > @@ -388,14 +389,16 @@ static int flctl_dma_fifo0_transfer(struct sh_flctl
> > *flctl, unsigned long *buf, goto out;
> >  	}
> > 
> > -	ret =
> > +	time_left =
> >  	wait_for_completion_timeout(&flctl->dma_complete,
> >  				msecs_to_jiffies(3000));
> > 
> > -	if (ret <= 0) {
> > +	if (time_left == 0) {
> >  		dmaengine_terminate_all(chan);
> >  		dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
> > -	}
> > +		ret = -ETIMEDOUT;
> > +	} else
> > +		ret = 1;	/* completion succeeded */
> 
> I'd go one step further and make this function return < 0 on error and 0 on 
> success, like usually done through the kernel API. You could then simplify the 
> code using something like
> 
>         if (!wait_for_completion_timeout(&flctl->dma_complete,
>                                          msecs_to_jiffies(3000))) {
>                 dmaengine_terminate_all(chan);
>                 dev_err(&flctl->pdev->dev, "wait_for_completion_timeout\n");
>                 ret = -ETIMEDOUT;
>         }
> 
> (pre-initializing ret to 0)
> 
> > 
> >  out:
> >  	reg = readl(FLINTDMACR(flctl));
>

ok - given that this needs some fixup anyway due to
not properly reading dmaengine_submit() - I'll fix
things up and re-submit.

thx!
hofrat
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