linux-kernel - Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to

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Date:	Wed, 1 Apr 2015 16:24:44 +0200
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Aaron Sierra <asierra@...-inc.com>
Cc:	Nicholas Mc Guire <hofrat@...dl.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	Joe Schultz <jschultz@...-inc.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time
	conversion

On Wed, 01 Apr 2015, Aaron Sierra wrote:

> ----- Original Message -----
> > From: "Nicholas Mc Guire" <hofrat@...dl.org>
> > Sent: Friday, March 13, 2015 6:23:47 AM
> > 
> > This is only an API consolidation and should make things more readable
> > it replaces var * HZ / 1000 by msecs_to_jiffies(var) which helps readability
> > and also handles all corner-cases properly.
> > 
> > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> > ---
> > 
> > Patch was compile tested with corenet64_smp_defconfig
> > (implies CONFIG_MTD_NAND_FSL_IFC=y)
> > 
> > Patch is against 4.0-rc3 (localversion-next is -next-20150313
> > 
> >  drivers/mtd/nand/fsl_ifc_nand.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/fsl_ifc_nand.c
> > b/drivers/mtd/nand/fsl_ifc_nand.c
> > index 4c05f4f..51394e5 100644
> > --- a/drivers/mtd/nand/fsl_ifc_nand.c
> > +++ b/drivers/mtd/nand/fsl_ifc_nand.c
> > @@ -317,7 +317,7 @@ static void fsl_ifc_run_command(struct mtd_info *mtd)
> >  
> >  	/* wait for command complete flag or timeout */
> >  	wait_event_timeout(ctrl->nand_wait, ctrl->nand_stat,
> > -			   IFC_TIMEOUT_MSECS * HZ/1000);
> > +			   msecs_to_jiffies(IFC_TIMEOUT_MSECS));
> 
> Nicholas,
> Your patch makes me think that this timeout value should be calculated
> once during initialization and stored in a new member of
> struct fsl_ifc_mtd. That would improve readability AND have some
> positive impact on performance.
>

is it not a bit wasteful to put it into struct fsl_ifc_mtd
which is used quite often in here ?

#define IFC_TIMEOUT msecs_to_jiffies(500)

sould do - its only referenced twice and would achieve what you
suggested - initializing it in one location and improved readability

	wait_event_timeout(ctrl->nand_wait, ctrl->nand_stat, IFC_TIMEOUT);

would there be any disadvantage of this solution?

thx!
hofrat
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