[PM-WIP-OPP][PATCH v3] pm: opp: twl/tps: optimize uv to vsel function

[PM-WIP-OPP][PATCH v3] pm: opp: twl/tps: optimize uv to vsel function

[Nishanth Menon]

From: Romit Dasgupta <romit@ti.com>

For integer values x and y; int div x / y causes truncation. Current
omap_twl_uv_to_vsel function implements an equivalent of ceil which
is based on an if condition to check truncation and round up. We can
do this in a more optimal manner without the if condition. The round
up is handled by adding the round off factor prior to truncation as:
(x + (y - 1)) / y

Cc: Kevin Hilman <khilman@deeprootsystems.com>
Acked-by: Nishanth Menon <nm@ti.com>

Signed-off-by: Romit Dasgupta <romit@ti.com>
---
Discussions:
v2: http://marc.info/?t=126318930800001&r=1&w=2
v1: http://marc.info/?t=126226623800006&r=1&w=2

 arch/arm/plat-omap/opp_twl_tps.c |   12 ++----------
 1 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/arch/arm/plat-omap/opp_twl_tps.c b/arch/arm/plat-omap/opp_twl_tps.c
index e0db39b..468fb97 100644
--- a/arch/arm/plat-omap/opp_twl_tps.c
+++ b/arch/arm/plat-omap/opp_twl_tps.c
@@ -36,14 +36,6 @@ unsigned long omap_twl_vsel_to_uv(const u8 vsel)
  */
 u8 omap_twl_uv_to_vsel(unsigned long uv)
 {
-	u8 vsel;
-
-	vsel = ((uv / 100) - 6000) / 125;
-
-	/* round off to higher voltage */
-	/* XXX Surely not the best way to handle this. */
-	if (uv > omap_twl_vsel_to_uv(vsel))
-		vsel++;
-
-	return vsel;
+	/* Round up to higher voltage */
+	return (((uv + 99) / 100 - 6000) + 124) / 125;
 }
-- 
1.6.3.3

Re: [PM-WIP-OPP][PATCH v3] pm: opp: twl/tps: optimize uv to vsel function

[Kevin Hilman]

Nishanth Menon <nm@ti.com> writes:

> From: Romit Dasgupta <romit@ti.com>
>
> For integer values x and y; int div x / y causes truncation. Current
> omap_twl_uv_to_vsel function implements an equivalent of ceil which
> is based on an if condition to check truncation and round up. We can
> do this in a more optimal manner without the if condition. The round
> up is handled by adding the round off factor prior to truncation as:
> (x + (y - 1)) / y
>
> Cc: Kevin Hilman <khilman@deeprootsystems.com>
> Acked-by: Nishanth Menon <nm@ti.com>
>
> Signed-off-by: Romit Dasgupta <romit@ti.com>

Thanks, adding to pm-wip-opp

Kevin

> ---
> Discussions:
> v2: http://marc.info/?t=126318930800001&r=1&w=2
> v1: http://marc.info/?t=126226623800006&r=1&w=2
>
>  arch/arm/plat-omap/opp_twl_tps.c |   12 ++----------
>  1 files changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm/plat-omap/opp_twl_tps.c b/arch/arm/plat-omap/opp_twl_tps.c
> index e0db39b..468fb97 100644
> --- a/arch/arm/plat-omap/opp_twl_tps.c
> +++ b/arch/arm/plat-omap/opp_twl_tps.c
> @@ -36,14 +36,6 @@ unsigned long omap_twl_vsel_to_uv(const u8 vsel)
>   */
>  u8 omap_twl_uv_to_vsel(unsigned long uv)
>  {
> -	u8 vsel;
> -
> -	vsel = ((uv / 100) - 6000) / 125;
> -
> -	/* round off to higher voltage */
> -	/* XXX Surely not the best way to handle this. */
> -	if (uv > omap_twl_vsel_to_uv(vsel))
> -		vsel++;
> -
> -	return vsel;
> +	/* Round up to higher voltage */
> +	return (((uv + 99) / 100 - 6000) + 124) / 125;
>  }
> -- 
> 1.6.3.3