Message-ID: <556D82FE.4010102@linaro.org>
Date: Tue, 02 Jun 2015 15:48:38 +0530
From: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
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To: Lee Jones <lee.jones@linaro.org>
CC: linux-arm-kernel@lists.infradead.org, robh+dt@kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        rtc-linux@googlegroups.com, sameo@linux.intel.com,
        a.zummo@towertech.it, alexandre.belloni@free-electrons.com,
        Chao Xie <chao.xie@marvell.com>
Subject: Re: [PATCH 4/4] mfd: 88pm800: allocate pdata->rtc if not allocated
 earlier
References: <1432937962-4537-1-git-send-email-vaibhav.hiremath@linaro.org> <1432937962-4537-5-git-send-email-vaibhav.hiremath@linaro.org> <20150601082200.GC3329@x1> <556D3A14.6050505@linaro.org> <20150602074004.GH3329@x1> <556D71F6.4030608@linaro.org> <20150602093323.GI3329@x1> <556D7C32.9080806@linaro.org> <20150602100739.GK3329@x1>
In-Reply-To: <20150602100739.GK3329@x1>
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On Tuesday 02 June 2015 03:37 PM, Lee Jones wrote:
> On Tue, 02 Jun 2015, Vaibhav Hiremath wrote:
>> On Tuesday 02 June 2015 03:03 PM, Lee Jones wrote:
>>> On Tue, 02 Jun 2015, Vaibhav Hiremath wrote:
>>>> On Tuesday 02 June 2015 01:10 PM, Lee Jones wrote:
>>>>> On Tue, 02 Jun 2015, Vaibhav Hiremath wrote:
>>>>>> On Monday 01 June 2015 01:52 PM, Lee Jones wrote:
>>>>>>> On Sat, 30 May 2015, Vaibhav Hiremath wrote:
>>>>>>>
>>>>>>>> RTC in pmic 88PM800 can run even the core is powered off, and user
>>>>>>>> can set alarm in RTC. When the alarm is timed out, the PMIC will power up
>>>>>>>> the core, and the whole system will boot up. And during PMIC driver probe,
>>>>>>>> it will read some register to find out whether this boot is caused by RTC
>>>>>>>> timeout or not, and pass on this information to the RTC driver.
>>>>>>>>
>>>>>>>> So we need rtc platform data to be existed in PMIC driver to pass this
>>>>>>>> information.
>>>>>>>>
>>>>>>>> Signed-off-by: Chao Xie <chao.xie@marvell.com>
>>>>>>>> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
>>>>>>>> ---
>>>>>>>>   drivers/mfd/88pm800.c | 19 +++++++++++++++++++
>>>>>>>>   1 file changed, 19 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/mfd/88pm800.c b/drivers/mfd/88pm800.c
>>>>>>>> index 8ea4467..34546a1 100644
>>>>>>>> --- a/drivers/mfd/88pm800.c
>>>>>>>> +++ b/drivers/mfd/88pm800.c
>>>>>>>> @@ -586,6 +586,25 @@ static int pm800_probe(struct i2c_client *client,
>>>>>>>>   			return ret;
>>>>>>>>   	}
>>>>>>>>
>>>>>>>> +	/*
>>>>>>>> +	 * RTC in pmic can run even the core is powered off, and user can set
>>>>>>>> +	 * alarm in RTC. When the alarm is time out, the PMIC will power up
>>>>>>>> +	 * the core, and the whole system will boot up. When PMIC driver is
>>>>>>>> +	 * probed, it will read out some register to find out whether this
>>>>>>>> +	 * boot is caused by RTC timeout or not, and it need pass this
>>>>>>>> +	 * information to RTC driver.
>>>>>>>> +	 * So we need rtc platform data to be existed to pass this information.
>>>>>>>> +	 */
>>>>>>>> +	if (!pdata->rtc) {
>>>>>>>> +		pdata->rtc = devm_kzalloc(&client->dev,
>>>>>>>> +					  sizeof(*(pdata->rtc)), GFP_KERNEL);
>>>>>>>> +		if (!pdata->rtc) {
>>>>>>>> +			dev_err(&client->dev,
>>>>>>>> +					"failed to allocate memory for rtc\n");
>>>>>>>> +			return -ENOMEM;
>>>>>>>> +		}
>>>>>>>> +	}
>>>>>>>> +
>>>>>>>
>>>>>>> Where is this memory first used?
>>>>>>>
>>>>>>
>>>>>> In the same file, look for field "rtc_wakeup".
>>>>>>
>>>>>> FYI,
>>>>>>
>>>>>> This field is used in two files,
>>>>>>
>>>>>> drivers/mfd/88pm800.c
>>>>>> and
>>>>>> drivers/rtc/rtc-88pm800.c	[sets the "platform_data" field]
>>>>>
>>>>> Then were is the platform_data field subsequently used?
>>>>
>>>> Currently not used, but it is for future use, where we would be
>>>> interested to know that the wakeup is really from reset or RTC wakeup.
>>>
>>> Well it was introduced 3 years ago, so the chances of it being "used
>>> in the future" are probably pretty low.  Unless of course, you are
>>> planning on submitting that code.  In which case, you can add this
>>> patch to that set and I can re-review it then.
>>>
>>>>> Looking at the RTC platform data declaration I see:
>>>>>
>>>>> struct pm80x_rtc_pdata {
>>>>>      int             vrtc;
>>>>>      int             rtc_wakeup;
>>>>> };
>>>>>
>>>>> Is 'vrtc' even used?  If so, where?
>>>>
>>>> No, it is not.
>>>
>>> So either submit a patch-set that makes use of them, or let me know
>>> that you're not going to do that and I'll remove it altogether.
>>> Likewise for rtc_wakeup.
>>>
>>
>> I am ok with vrtc field, we can remove it.
>
> Okay, I will do so, thanks.
>
>> But,
>> I would recommend _not_ to remove rtc_wakeup, as it may not be used
>> immediately, but still have logical significance.
>>
>> Consuming rtc_wakeup in the code is dependant on overall power
>> management support, which is always long pole for development. As you
>> would have seen, we have just started with baseport for pxa1928 and I
>> am starting on upstreaming driver part.
>>
>>
>>  From hardware perspective, this is important feature, where it indicate
>> whether the boot was triggered by reset assertion or by RTC wakeup. So
>> as of now from driver perspective I feel no harm to have one field for
>> this.
>>
>> Finally, its your call. I will let you decide.
>> The field can be added later when it actually gets consumed.
>
> I will not remove the wake-up field.  Equally, I will not accept code
> which allocates memory for it whilst it is not being used.
>


Not an issue.
As I said, it can be added later when we actually consume it.

Thanks,
Vaibhav
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