Messages in this thread | | | Date | Mon, 16 Jul 2012 14:41:06 +0530 | From | Rajendra Nayak <> | Subject | Re: [PATCH RFT 1/2] regulator: twl: Fix the formula to calculate vsel and voltage for twl6030ldo |
| |
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 > >
-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |