linux-kernel - Re: [PATCHv3] w1: omap-hdq: Simplify driver with PM runtime autosuspend

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Message-Id: <6430AF54-849E-456B-8DB0-B4478BBDB78D@goldelico.com>
Date:   Fri, 17 Apr 2020 16:52:15 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     Tony Lindgren <tony@...mide.com>,
        Evgeniy Polyakov <zbr@...emap.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Adam Ford <aford173@...il.com>,
        "Andrew F . Davis" <afd@...com>, Vignesh R <vigneshr@...com>
Subject: Re: [PATCHv3] w1: omap-hdq: Simplify driver with PM runtime autosuspend


> Am 17.04.2020 um 16:43 schrieb Andreas Kemnade <andreas@...nade.info>:
> 
> On Fri, 17 Apr 2020 16:22:47 +0200
> "H. Nikolaus Schaller" <hns@...delico.com> wrote:
> 
>>> Am 16.04.2020 um 20:46 schrieb Tony Lindgren <tony@...mide.com>:
>>> 
>>> * H. Nikolaus Schaller <hns@...delico.com> [200416 15:04]:  
>>>> Hi Tony,
>>>> it looks as if something with this patch is broken on GTA04. For v5.6 and v5.7-rc1.
>>>> 
>>>> HDQ battery access times out after ca. 15 seconds and I get temperature of -273.1°C...
>>>> 
>>>> Reverting this patch and everything is ok again.  
>>> 
>>> Hmm OK interesting.
>>> 
>>>> What is "ti,mode" about? Do we have that (indirectly) in gta04.dtsi?
>>>> Or does this patch need some CONFIGs we do not happen to have?  
>>> 
>>> Sounds like you have things working though so there should be no
>>> need for having ti,mode = "1w" in the dts.
>>> 
>>>>> 	pm_runtime_enable(&pdev->dev);
>>>>> +	pm_runtime_use_autosuspend(&pdev->dev);
>>>>> +	pm_runtime_set_autosuspend_delay(&pdev->dev, 300);  
>>> 
>>> Care to check if changing pm_runtime_set_autosuspend_delay value
>>> to -1 in probe makes the issue go away? Or change it manually
>>> to -1 via sysfs.
>>> 
>>> If that helps, likely we have a missing pm_runtime_get_sync()
>>> somewhere in the driver.  
>> 
>> Yes, it does! It suffices to set it to -1 for one readout.
>> Aything else I can test?
>> 
> How does it depend on loaded drivers?
> Is it really mainline kernel + config + devicetree or something else?

Well, I can revert the patch on the same
kernel (5.6 or 5.7-rc1) + config + devicetree + user-space
and the problem is gone.

This means that something is different between the old and the new
version which makes the hdq access delayed and failing. Of course I
don't know the reason for it and what does influence it.

> 
> Can you reproduce the problem with init=/bin/bash
> and then mount sysfs and modprobe omap_hdq?

I am not sure how quickly I can test such a setup.

> Regarding pm_runtime stuff I thought I have the worst case scenario.

What may make a difference is the sequence in which drivers are loaded.

BR,
Nikolaus