linux-kernel - Re: [PATCH 1/2] PCI: dwc: dra7xx: Create functional dependency between PCIe and PHY

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Date:   Tue, 10 Oct 2017 10:59:18 +0300
From:   Roger Quadros <rogerq@...com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     <linux-omap@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <nsekhar@...com>
Subject: Re: [PATCH 1/2] PCI: dwc: dra7xx: Create functional dependency
 between PCIe and PHY


Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

On 10/10/17 10:42, Kishon Vijay Abraham I wrote:
> Roger,
> 
> On Tuesday 10 October 2017 12:49 PM, Roger Quadros wrote:
>> On 09/10/17 12:03, Kishon Vijay Abraham I wrote:
>>> PCI core access configuration space registers in resume_noirq callbacks.
>>> In the case of dra7xx, PIPE3 PHY connected to PCIe controller has to be
>>> enabled before accessing configuration space registers. Since
>>> PIPE3 PHY is enabled by only configuring control module registers, no
>>> aborts has been observed so far (though during noirq stage, interface
>>> clock of PIPE3 PHY is not enabled).
>>>
>>> With new TRM updates, PIPE3 PHY has to be initialized (PIPE3 PHY
>>> registers has to be accessed) as well which requires the interface
>>> clock of PIPE3 PHY to be enabled. The interface clock of PIPE3 PHY is
>>> derived from OCP2SCP and hence PCIe PHY is modeled as a child of
>>> OCP2SCP. Since pm_runtime is not enabled during noirq stage,
>>> pm_runtime_get_sync done in phy_init doesn't enable
>>> OCP2SCP clocks resulting in abort when PIPE3 PHY registers are
>>> accessed.
>>
>> This could be the case not only with PCIe but even with USB and SATA?
> 
> right, if USB/SATA driver has no_irq callbacks then the same issue might occur.

OK. Is this something that we should document in Documentation/phy.txt?

> But looks like none of them uses no_irq callbacks.

>> Maybe today it doesn't complain because USB/SATA is being resumed (by chance) after PHY?
> 
> But once pm_runtime is enabled, USB/SATA can enable PHY which in turn will
> enable OCP2SCP and PHY can be accessed without any issues.
> 
> Thanks
> Kishon
> 

-- 
cheers,
-roger