linux-kernel - [Query] Enabling parent device clock from resume

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Message-ID: <62cd5ee0-3f0c-5e65-5f64-0c91a2a6f1e6@ti.com>
Date:   Tue, 18 Apr 2017 11:37:20 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>, <khilman@...nel.org>,
        <rnayak@...eaurora.org>, Paul Walmsley <paul@...an.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "Nori, Sekhar" <nsekhar@...com>, "Kristo, Tero" <t-kristo@...com>
Subject: [Query] Enabling parent device clock from resume_noirq

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?

Thanks
Kishon