[PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[Nicholas Mc Guire]

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@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));
 
 	/* ctrl->nand_stat will be updated from IRQ context */
 	if (!ctrl->nand_stat)
@@ -860,7 +860,7 @@ static void fsl_ifc_sram_init(struct fsl_ifc_mtd *priv)
 
 	/* 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));
 
 	if (ctrl->nand_stat != IFC_NAND_EVTER_STAT_OPC)
 		printk(KERN_ERR "fsl-ifc: Failed to Initialise SRAM\n");
-- 
1.7.10.4

Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[Aaron Sierra]

----- Original Message -----
> From: "Nicholas Mc Guire" <hofrat@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 <hofrat@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.

-Aaron S.

>  
>  	/* ctrl->nand_stat will be updated from IRQ context */
>  	if (!ctrl->nand_stat)
> @@ -860,7 +860,7 @@ static void fsl_ifc_sram_init(struct fsl_ifc_mtd *priv)
>  
>  	/* 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));
>  
>  	if (ctrl->nand_stat != IFC_NAND_EVTER_STAT_OPC)
>  		printk(KERN_ERR "fsl-ifc: Failed to Initialise SRAM\n");
> --
> 1.7.10.4
> 
> 

Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[Nicholas Mc Guire]

On Wed, 01 Apr 2015, Aaron Sierra wrote:

> ----- Original Message -----
> > From: "Nicholas Mc Guire" <hofrat@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 <hofrat@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 ?

#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

Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[Aaron Sierra]

----- Original Message -----
> From: "Nicholas Mc Guire" <der.herr@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" <hofrat@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 <hofrat@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.

Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[Joe Perches]

On Wed, 2015-04-01 at 10:08 -0500, Aaron Sierra wrote:
> ----- Original Message -----
> > From: "Nicholas Mc Guire" <der.herr@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" <hofrat@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 <hofrat@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 ?cho
> 
> 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.

Nicholas, any progress on that builtin_const_p variant

Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[Nicholas Mc Guire]

On Wed, 01 Apr 2015, Joe Perches wrote:

> On Wed, 2015-04-01 at 10:08 -0500, Aaron Sierra wrote:
> > ----- Original Message -----
> > > From: "Nicholas Mc Guire" <der.herr@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" <hofrat@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 <hofrat@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 ?cho
> > 
> > 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.
> 
> Nicholas, any progress on that builtin_const_p variant
>
did not get to it yet - but thats the next thing
on my fun list.

thx!
hofrat

Re: [PATCH] mtd: fsl_ifc_nand: use msecs_to_jiffies for time conversion

[Brian Norris]

On Fri, Mar 13, 2015 at 07:23:47AM -0400, Nicholas Mc Guire wrote:
> 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@osadl.org>

Pushed to l2-mtd.git.

I'm not sure the objections about an extra function call are important
right now; if they are, then it shouldn't be too hard to patch in a
__builtin_constant_p() variant of msecs_to_jiffies(), as Joe suggested.

Brian