Romit Dasgupta said the following on 01/12/2010 02:58 AM:
Kevin Hilman wrote:
Romit Dasgupta <romit@xxxxxx> 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 -0000
From: Dasgupta, Romit <romit@xxxxxx>
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 <romit@xxxxxx>
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;
}
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
