From: Kishon Vijay Abraham I <kishon@ti.com>
To: Grygorii Strashko <grygorii.strashko@ti.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>, <khilman@kernel.org>,
<rnayak@codeaurora.org>, Paul Walmsley <paul@pwsan.com>,
Bjorn Helgaas <helgaas@kernel.org>,
"Nori, Sekhar" <nsekhar@ti.com>, "Kristo, Tero" <t-kristo@ti.com>,
<linux-pm@vger.kernel.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Alan Stern <stern@rowland.harvard.edu>
Subject: Re: [Query] Enabling parent device clock from resume_noirq
Date: Wed, 19 Apr 2017 16:40:20 +0530 [thread overview]
Message-ID: <23a79524-0445-e9cb-2e51-2dd2e37e4f5b@ti.com> (raw)
In-Reply-To: <4c6e91e4-35fa-2fde-7915-fb922ec22567@ti.com>
Hi,
On Wednesday 19 April 2017 01:35 AM, Grygorii Strashko wrote:
> + linux-pm
>
> On 04/18/2017 01:07 AM, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> resume_noirq callbacks are used in PCIe core to restore PCI state (this
>> accesses PCI module). So the clocks of PCI module has to be enabled before
>> resume_noirq.
>>
>> The clocks for the PCI module in DRA7xx is provided by PIPE3 PHY device which
>> in turn gets it's clock from OCP2SCP device. During resume_noirq callbacks,
>> pm_runtime is disabled, so pm_runtime_get_sync is ineffective. However
>> pm_runtime can be enabled using pm_runtime_force_resume. Now the problem is
>> adding pm_runtime_force_resume() in resume_noirq callback of pci-dra7xx driver
>> will enable only the pm_runtime of PCI device but not PIPE3 PHY or OCP2SCP.
>> Adding pm_runtime_force_resume() in resume_noirq callback of PIPE3 PHY driver
>> or OCP2SCP driver will not help if the resume_noirq callbacks in PIP3PHY driver
>> and OCP2SCP driver are invoked after the resume_noirq of pci-dra7xx driver.
>>
>> How to enable the pm_runtime of parent devices in resume_noirq callback? Does
>> existing pm_runtime framework has support for that?
>>
>
> Most probably you've hit the issue described in [1].
> In general, if pci-dra7xx is consumer of PIPE3 PHY device and
> PIPE3 PHY device is child of OCP2SCP then suspend/resume order should be
> - pci-dra7xx
> - PIPE3 PHY
> - OCP2SCP
> and resume
> - OCP2SCP
> - PIPE3 PHY
> - pci-dra7xx
> and in this case pm_runtime_force_x() might work.
>
> Hence, approach [1] was not accepted (personally I still like it) and
> "Functional dependencies tracking support" was introduced instead by commit 9ed9895 [2]
> you can try it.
>
> But, as per code, I'm not sure that Functional dependencies properly tracked in
> pm_runtime_force_x() functions.
>
> PS: you can try to reorder device's nodes in DT and place PCI node after "ocp2scp" :P
reordering helps ;-) I'll try the functional dependencies.
Thanks for the hint :-)
Cheers
Kishon
prev parent reply other threads:[~2017-04-19 11:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-18 6:07 [Query] Enabling parent device clock from resume_noirq Kishon Vijay Abraham I
2017-04-18 20:05 ` Grygorii Strashko
2017-04-19 11:10 ` Kishon Vijay Abraham I [this message]
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