* Re: [PATCH RFT 1/2] regulator: twl: Fix the formula to calculate vsel and voltage for twl6030ldo
[not found] ` <1341831686.4343.7.camel@phoenix>
@ 2012-07-15 21:00 ` Mark Brown
2012-07-16 9:11 ` Rajendra Nayak
1 sibling, 0 replies; 3+ messages in thread
From: Mark Brown @ 2012-07-15 21:00 UTC (permalink / raw)
To: Axel Lin
Cc: Rajendra Nayak, Peter Ujfalusi, Liam Girdwood, linux-kernel,
linux-omap
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On Mon, Jul 09, 2012 at 07:01:26PM +0800, Axel Lin wrote:
> I found a problem that before commit 3e3d3be79c, the voltage tables were
> not linear mapping. So why we can convert these voltage mapping table to
> Voltage(in mV) = 1000mv + 100mv * (vsel - 1)?
Guys, it's pretty concerning that there's been no response at all to
this. Looking at the changes Axel's statement above is accurate for at
least VAUX1 and VMMC, I didn't check all the regulators, so either the
original code was buggy or there's an issue that needs fixing in the
current code.
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH RFT 1/2] regulator: twl: Fix the formula to calculate vsel and voltage for twl6030ldo
[not found] ` <1341831686.4343.7.camel@phoenix>
2012-07-15 21:00 ` [PATCH RFT 1/2] regulator: twl: Fix the formula to calculate vsel and voltage for twl6030ldo Mark Brown
@ 2012-07-16 9:11 ` Rajendra Nayak
2012-07-16 10:20 ` Axel Lin
1 sibling, 1 reply; 3+ messages in thread
From: Rajendra Nayak @ 2012-07-16 9:11 UTC (permalink / raw)
To: Axel Lin; +Cc: Mark Brown, Peter Ujfalusi, Liam Girdwood, linux-kernel, loml
Hi Axel,
My apologies for the delay in responding to this one.
On Monday 09 July 2012 04:31 PM, Axel Lin wrote:
> 於 一，2012-07-09 於 11:22 +0800，Axel Lin 提到：
>> In twl6030ldo_set_voltage, current code use below formula to calculate vsel:
>> vsel = (min_uV/1000 - 1000)/100 + 1;
>> This is worng because when min_uV is 1000000 uV, vsel is 1.
>> It should be 0 in this case.
Why? Do you know of any documentation which states this?
I am referring to the twl6030 Top Functional spec version 1.18
and Table - 223 "LDO Output Voltage Selection Code" clearly
states that the vsel should be 1 when voltage expected is 1000000 uV.
Also refer to equation 3 "LDO Output Voltage Selection Code" in the
same document and you will see this mentioned..
Absolute Voltage value = 1.0V + 0.1V * (binary value – 00000001)
>> Fix it by change the equation to: (This equation is common for linear mapping)
>> vsel = DIV_ROUND_UP(min_uV - rdev->desc->min_uV, rdev->desc->uV_step);
>>
>> In twl6030ldo_get_voltage, current code use below formula to calculate voltage:
>> mV = 1000mv + 100mv * (vsel - 1)
>> This is worng because when vsel is 0, mV is 900mV. Note the min_uV is 1000mV.
>> Fix it by change the equation to: (This equation is common for linear mapping)
>> return rdev->desc->min_uV + vsel * rdev->desc->uV_step;
>
> While I'm thinking I need to rework this patch so that it doesn't use
> rdev->desc->min_uV and rdev->desc->uV_step and then can be applied
> to current Linus' tree.
>
> But while I am tracking back to commit 3e3d3be79c
> Author: Rajendra Nayak<rnayak@ti.com>
> Date: Thu Apr 22 14:18:32 2010 +0530
>
> twl6030: regulator: Remove vsel tables and use formula for
> calculation
>
> All twl6030 regulators can be programmed from 1.0v to 3.3v
> with 100mV steps.
> The below formula can be used to calculate the vsel values
> to be programmed in the VREG_VOLTAGE registers.
>
> Voltage(in mV) = 1000mv + 100mv * (vsel - 1)
>
> Ex: if vsel = 0x9, mV = 1000 + 100 * (9 -1) = 1800mV.
>
> This patch removes all existing VSEL tables for twl6030 adjustable
> regulators and just uses the formula directly for vsel calculations
> after verifing they fall in the allowed range.
>
> Signed-off-by: Rajendra Nayak<rnayak@ti.com>
>
> I found a problem that before commit 3e3d3be79c, the voltage tables were
> not linear mapping. So why we can convert these voltage mapping table to
> Voltage(in mV) = 1000mv + 100mv * (vsel - 1)?
>
> Did I miss something?
All voltage tables before commit '3e3d3be79c' for twl6030 regulators
were clearly wrong. They assumed similarity with twl4030 regulators
which was not right.
regards,
Rajendra
>
> Regards,
> Axel
>
>
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^ permalink raw reply [flat|nested] 3+ messages in thread