----- Original Message ----- > From: "Nicholas Mc Guire" <der.h...@hofr.at> > Sent: Wednesday, April 1, 2015 9:24:44 AM > > On Wed, 01 Apr 2015, Aaron Sierra wrote: > > > ----- Original Message ----- > > > From: "Nicholas Mc Guire" <hof...@osadl.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 <hof...@osadl.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 ?
Storing the timeout in the private structure would use 4 or 8 bytes, but the structure is passed around as pointer reference, so there is no added overhead there. > #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? I don't have an issue with the compactness of your code. The issue to me is that msecs_to_jiffies() is a real function call, not a macro. That means that there would be a branch to that function followed by a non-trivial calculation *every* time fsl_ifc_run_command() is called. If the timeout value were calculated during init, then the cost of accessing it would simply a pointer dereference. -Aaron S. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
