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Message-ID: <b0c20fac-9f4c-dff2-abef-cd79b1f1ae0a@roeck-us.net>
Date: Fri, 18 Nov 2016 06:09:13 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Tom Levens <tom.levens@...n.ch>
Cc: jdelvare@...e.com, robh+dt@...nel.org, mark.rutland@....com,
linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] hwmon: ltc2990: refactor value conversion
On 11/18/2016 12:18 AM, Tom Levens wrote:
> Hi Guenter,
>
> On Thu, 17 Nov 2016, Guenter Roeck wrote:
>
>> On 11/17/2016 08:23 AM, Tom Levens wrote:
>>> Hi Guenter,
>>>
>>> Thanks for taking the time to review the patch.
>>>
>>> On Thu, 17 Nov 2016, Guenter Roeck wrote:
>>>
>>> > Hi Tom,
>>> > > On 11/17/2016 04:10 AM, Tom Levens wrote:
>>> > > Conversion from raw values to signed integers has been refactored > > using
>>> > > the macros in bitops.h.
>>> > > > Please also mention that this fixes a bug in negative temperature > conversions.
>>>
>>> Yes, of course, I will include the information in v3.
>>>
>>> > > > Signed-off-by: Tom Levens <tom.levens@...n.ch>
>>> > > ---
>>> > > drivers/hwmon/ltc2990.c | 27 ++++++++++-----------------
>>> > > 1 files changed, 10 insertions(+), 17 deletions(-)
>>> > > > > diff --git a/drivers/hwmon/ltc2990.c b/drivers/hwmon/ltc2990.c
>>> > > index 8f8fe05..0ec4102 100644
>>> > > --- a/drivers/hwmon/ltc2990.c
>>> > > +++ b/drivers/hwmon/ltc2990.c
>>> > > @@ -9,8 +9,12 @@
>>> > > * This driver assumes the chip is wired as a dual current monitor, > > and
>>> > > * reports the voltage drop across two series resistors. It also > > reports
>>> > > * the chip's internal temperature and Vcc power supply voltage.
>>> > > + *
>>> > > + * Value conversion refactored
>>> > > + * by Tom Levens <tom.levens@...n.ch>
>>> > > Kind of unusual to do that for minor changes like this. Imagine if > everyone would do that.
>>> > The commit log is what gives you credit.
>>>
>>> Good point, thanks for the hint. I will remove it from v3.
>>>
>>> > > */
>>> > > > > +#include <linux/bitops.h>
>>> > > #include <linux/err.h>
>>> > > #include <linux/hwmon.h>
>>> > > #include <linux/hwmon-sysfs.h>
>>> > > @@ -34,19 +38,10 @@
>>> > > #define LTC2990_CONTROL_MODE_CURRENT 0x06
>>> > > #define LTC2990_CONTROL_MODE_VOLTAGE 0x07
>>> > > > > -/* convert raw register value to sign-extended integer in 16-bit > > range */
>>> > > -static int ltc2990_voltage_to_int(int raw)
>>> > > -{
>>> > > - if (raw & BIT(14))
>>> > > - return -(0x4000 - (raw & 0x3FFF)) << 2;
>>> > > - else
>>> > > - return (raw & 0x3FFF) << 2;
>>> > > -}
>>> > > -
>>> > > /* Return the converted value from the given register in uV or mC */
>>> > > -static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, int > > *result)
>>> > > +static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, s32 > > *result)
>>> > > {
>>> > > - int val;
>>> > > + s32 val;
>>> > > Please just leave the variable type alone. it is also used for the > return value
>>> > from i2c_smbus_read_word_swapped(), which is an int, and changing it to > s32 doesn't really make the code better.
>>>
>>> According to i2c.h the return type for i2c_smbus_read_word_swapped() is
>>> s32, which is why I modified it here. But it could be changed back if you
>>> think it is better to leave it as an int.
>>>
>> Ah, ok. Good to know. Please leave it anyway, reason being that there is no real
>> reason to change it. Effectively those are just whitespace changes (unlike the rest,
>> which is part bug fix, part cleanup).
>>
>>> > Can you send me a register map for the chip ? I would like to write a > module test.
>>>
>>> Here is an example register dump:
>>
>> I meant the output of i2cdump (something like "i2cdump -y -f <bus> <i2c-address> w").
>>
>
> The register map wraps at 0x0F, so I only sent you the first 16 bytes. But the fully expanded form is:
>
> 0 1 2 3 4 5 6 7 8 9 a b c d e f
> 00: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 10: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 20: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 30: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 40: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 50: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 60: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 70: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 80: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 90: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> a0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> b0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> c0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> d0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> e0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> f0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
Sorry, I wasn't clear. The chip uses 16-bit registers, so the
"w" in the command would be important to report the entire
register content, not just the first 8 bit of each register.
Thanks,
Guenter
>
> Cheers,
>
>> Thanks,
>> Guenter
>>
>>>
>>> 00 00 00 00
>>> 01 90 07 d0
>>> 2c cd 7d 80
>>> 7c 29 20 00
>>>
>>> The expected values in this case are:
>>>
>>> in0_input 5000
>>> in1_input 610
>>> in2_input 3500
>>> in3_input -195
>>> in4_input -299
>>> temp1_input 25000
>>> temp2_input 125000
>>> temp3_input -40000
>>> curr1_input 38840
>>> curr2_input -12428
>>>
>>> Testing with lltc,mode set to <5>, <6> and <7> should give you all
>>> measurements.
>>>
>>> > Thanks,
>>> > Guenter
>>>
>>> Cheers,
>>>
>>
>>
>
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