linux-kernel - Re: [PATCH 4/4] mfd: 88pm800: allocate pdata->rtc if not allocated earlier

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Message-ID: <20150602100739.GK3329@x1>
Date:	Tue, 2 Jun 2015 11:07:39 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Vaibhav Hiremath <vaibhav.hiremath@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, robh+dt@...nel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	rtc-linux@...glegroups.com, sameo@...ux.intel.com,
	a.zummo@...ertech.it, alexandre.belloni@...e-electrons.com,
	Chao Xie <chao.xie@...vell.com>
Subject: Re: [PATCH 4/4] mfd: 88pm800: allocate pdata->rtc if not allocated
 earlier

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@...vell.com>
> >>>>>>Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@...aro.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.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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