Re: [PM-WIP-OPP] [PATCH] cleaner ceil function for uv to vsel conversion
>> The description of the problem is "Cleaner ceil function for uv to vsel >> conversion". >> >> I think this patch is simple enough for people on this list to understand the >> optimization. I am sorry I cant be more descriptive. >> >> > here is a try: > - > > From patchwork Thu Dec 31 13:29:05 2009 > Content-Type: text/plain; charset="utf-8" > MIME-Version: 1.0 > Content-Transfer-Encoding: 7bit > Subject: [pm-wip-opp] [PATCH] opp: twl/tps: optimize uv to vsel function > Date: Thu, 31 Dec 2009 13:29:05 - > From: Dasgupta, Romit > X-Patchwork-Id: 70374 > > > 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 > Wow that is nice... Please send it if you can and add your Signed-off for the work! -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PM-WIP-OPP] [PATCH] cleaner ceil function for uv to vsel conversion
Romit Dasgupta said the following on 01/12/2010 02:58 AM:
Kevin Hilman wrote:
Romit Dasgupta writes:
Cleaner ceil function.
Needs better subject and better changelog.
Subject should probably be something like: OMAP:
[PATCH] OPP: TWL/TPS: optimize uv to vsel function
And changelog should describe the motiviation for the patch or a
description of the problem you're trying to solve.
The description of the problem is "Cleaner ceil function for uv to vsel
conversion".
I think this patch is simple enough for people on this list to understand the
optimization. I am sorry I cant be more descriptive.
here is a try:
-
From patchwork Thu Dec 31 13:29:05 2009
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [pm-wip-opp] [PATCH] opp: twl/tps: optimize uv to vsel function
Date: Thu, 31 Dec 2009 13:29:05 -
From: Dasgupta, Romit
X-Patchwork-Id: 70374
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
---
Currently putting signed-off in --- section. If Romit is ok, please
re-send as needed.
Signed-off-by: Dasgupta, Romit
diff --git a/arch/arm/plat-omap/opp_twl_tps.c
b/arch/arm/plat-omap/opp_twl_tps.c
index e0db39b..43dee2d 100644
--- a/arch/arm/plat-omap/opp_twl_tps.c
+++ b/arch/arm/plat-omap/opp_twl_tps.c
@@ -36,14 +36,7 @@ unsigned long omap_twl_vsel_to_uv(const u8 vsel)
*/
u8 omap_twl_uv_to_vsel(unsigned long uv)
{
-u8 vsel;
+/* Takes care of precision loss due to integer division */
+return (((uv + 99) / 100 - 6000) + 124) / 125;
-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;
}
--
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Re: [PM-WIP-OPP] [PATCH] cleaner ceil function for uv to vsel conversion
Kevin Hilman wrote: > Romit Dasgupta writes: > >> Cleaner ceil function. > > Needs better subject and better changelog. > > Subject should probably be something like: OMAP: > > [PATCH] OPP: TWL/TPS: optimize uv to vsel function > > And changelog should describe the motiviation for the patch or a > description of the problem you're trying to solve. The description of the problem is "Cleaner ceil function for uv to vsel conversion". I think this patch is simple enough for people on this list to understand the optimization. I am sorry I cant be more descriptive. > IOW, is this a > correctness fix, or an optimization, etc. Looks to me like it's tring > to compensate for some rounding issues, but please describe in detail > in the changelog. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PM-WIP-OPP] [PATCH] cleaner ceil function for uv to vsel conversion
Romit Dasgupta writes:
> Cleaner ceil function.
Needs better subject and better changelog.
Subject should probably be something like: OMAP:
[PATCH] OPP: TWL/TPS: optimize uv to vsel function
And changelog should describe the motiviation for the patch or a
description of the problem you're trying to solve. IOW, is this a
correctness fix, or an optimization, etc. Looks to me like it's tring
to compensate for some rounding issues, but please describe in detail
in the changelog.
Thanks,
Kevin
> Signed-off-by: Romit Dasgupta
> ---
> diff --git a/arch/arm/plat-omap/opp_twl_tps.c
> b/arch/arm/plat-omap/opp_twl_tps.c
> index e0db39b..1caa414 100644
> --- a/arch/arm/plat-omap/opp_twl_tps.c
> +++ b/arch/arm/plat-omap/opp_twl_tps.c
> @@ -36,14 +36,7 @@ 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;
> + return (((uv + 99) / 100 - 6000) + 124) / 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;
> }
--
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[PM-WIP-OPP] [PATCH] cleaner ceil function for uv to vsel conversion
Cleaner ceil function.
Signed-off-by: Romit Dasgupta
---
diff --git a/arch/arm/plat-omap/opp_twl_tps.c b/arch/arm/plat-omap/opp_twl_tps.c
index e0db39b..1caa414 100644
--- a/arch/arm/plat-omap/opp_twl_tps.c
+++ b/arch/arm/plat-omap/opp_twl_tps.c
@@ -36,14 +36,7 @@ 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;
+ return (((uv + 99) / 100 - 6000) + 124) / 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;
}
--
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