Re: [PATCH V2 2/2] thermal: broadcom: add Northstar thermal driver

["Rafał Miłecki" <rafal@milecki.pl>]

On 03/31/2017 04:23 PM, Jon Mason wrote:
> On Fri, Mar 31, 2017 at 3:03 AM, Rafał Miłecki <zajec5@gmail.com> wrote:
>> On 03/24/2017 03:35 PM, Jon Mason wrote:
>>>
>>> On Thu, Mar 23, 2017 at 11:30:45PM +0100, Rafał Miłecki wrote:
>>>>
>>>> diff --git a/drivers/thermal/broadcom/ns-thermal.c
>>>> b/drivers/thermal/broadcom/ns-thermal.c
>>>> new file mode 100644
>>>> index 000000000000..acf3a4de62a4
>>>> --- /dev/null
>>>> +++ b/drivers/thermal/broadcom/ns-thermal.c
>>>> @@ -0,0 +1,98 @@
>>>> +/*
>>>> + * Copyright (C) 2017 Rafał Miłecki <rafal@milecki.pl>
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License version 2 as
>>>> + * published by the Free Software Foundation.
>>>> + */
>>>> +
>>>> +#include <linux/module.h>
>>>> +#include <linux/of_address.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/thermal.h>
>>>> +
>>>> +#define PVTMON_CONTROL0                                        0x00
>>>> +#define PVTMON_CONTROL0_SEL_MASK                       0x0000000e
>>>> +#define PVTMON_CONTROL0_SEL_TEMP_MONITOR               0x00000000
>>>> +#define PVTMON_CONTROL0_SEL_TEST_MODE                  0x0000000e
>>>> +#define PVTMON_STATUS                                  0x08
>>>> +
>>>> +struct ns_thermal {
>>>> +       void __iomem *pvtmon;
>>>> +};
>>>> +
>>>> +static int ns_thermal_get_temp(void *data, int *temp)
>>>> +{
>>>> +       struct ns_thermal *ns_thermal = data;
>>>> +       u32 val;
>>>> +
>>>> +       val = readl(ns_thermal->pvtmon + PVTMON_CONTROL0);
>>>> +       if ((val & PVTMON_CONTROL0_SEL_MASK) !=
>>>> PVTMON_CONTROL0_SEL_TEMP_MONITOR) {
>>>> +               val &= ~PVTMON_CONTROL0_SEL_MASK;
>>>> +               val |= PVTMON_CONTROL0_SEL_TEMP_MONITOR;
>>>
>>>
>>> I think this is slightly confusing here.  If this was off, ORing in 0
>>> will not enable it.  I think we need to flip the #define to make it
>>> PVTMON_CONTROL0_SEL_TEMP_MONITOR_DISABLE (or a less crappy name).
>>> then use this line here to toggle it.  Something like
>>>
>>>                 val &= ~PVTMON_CONTROL0_SEL_TEMP_MONITOR_DISABLE;
>>
>>
>> I don't understand this, can you help me further?
>>
>> OR-ing with 0 is only a cosmetic thing obviously - just to make it clear
>> which
>> value we expect to be set in bits 1:3. The important part is:
>> val &= ~PVTMON_CONTROL0_SEL_MASK;
>
> You are using a side effect of the masking to clear/enable the block.
> I'm simply saying that we should be explicit about enabling it.  My
> concern is that using the side effect hides what is being done and
> could result in a bug somewhere down the line.  I think this is
> improbable based on the code, but wanted to err on the side of
> caution.

Well, I'm clearing current mode selection and "selecting" the mode I want. By
OR-ing PVTMON_CONTROL0_SEL_TEMP_MONITOR I'm clearly indicating I want temp
monitor more.

How else I could make it more obvious? Should I add some comment maybe?

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