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

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Date:   Wed, 18 Oct 2017 17:42:05 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Roger Quadros <rogerq@...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

Hi,

On Tuesday 10 October 2017 01:29 PM, Roger Quadros wrote:
> 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?

Yeah it could be but the dependency is not required for a lot of phy consumer
drivers.
Do you think it makes sense to create functional dependency between phy and
it's consumers in phy_get?

Thanks
Kishon