linux-kernel - Re: [PATCH V5 10/16] dt-bindings: PCI: tegra: Add device tree support for T194

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Message-ID: <4b1fe488-c99f-3deb-e6f0-a67eb65b2278@nvidia.com>
Date:   Tue, 14 May 2019 11:55:48 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     Rob Herring <robh@...nel.org>
CC:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        <linux-pci@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>, <kthota@...dia.com>,
        Manikanta Maddireddy <mmaddireddy@...dia.com>,
        <sagar.tv@...il.com>
Subject: Re: [PATCH V5 10/16] dt-bindings: PCI: tegra: Add device tree support
 for T194

On 5/13/2019 8:50 PM, Rob Herring wrote:
> On Tue, May 7, 2019 at 4:20 AM Vidya Sagar <vidyas@...dia.com> wrote:
>>
>> On 4/26/2019 9:13 PM, Rob Herring wrote:
>>> On Wed, Apr 24, 2019 at 10:49:58AM +0530, Vidya Sagar wrote:
>>>> Add support for Tegra194 PCIe controllers. These controllers are based
>>>> on Synopsys DesignWare core IP.
>>>>
>>>> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
>>>> ---
> 
>>>> +- nvidia,bpmp: Must contain a phandle to BPMP controller node.
>>>> +- nvidia,controller-id : Controller specific ID
>>>> +    0: C0
>>>> +    1: C1
>>>> +    2: C2
>>>> +    3: C3
>>>> +    4: C4
>>>> +    5: C5
>>>
>>> We don't normal put device indexes into DT. Why do you need this.
>>> Perhaps for accessing the BPMP? If so, make nvidia,bpmp a phandle+cell.
>> BPMP needs to know the controller number to enable it hence it needs to be
>> passed to BPMP. Just for accessing BPMP, I already added 'nvidia,bpmp' property.
> 
> Then make nvidia,bpmp take the phandle and this number.
Ok. I'll take care of it in next patch series.

> 
> 
>>>> +- nvidia,disable-aspm-states: Controls advertisement of ASPM states
>>>> +    bit-0 to '1': Disables advertisement of ASPM-L0s
>>>> +    bit-1 to '1': Disables advertisement of ASPM-L1. This also disables
>>>> +                   advertisement of ASPM-L1.1 and ASPM-L1.2
>>>> +    bit-2 to '1': Disables advertisement of ASPM-L1.1
>>>> +    bit-3 to '1': Disables advertisement of ASPM-L1.2
>>>
>>> Can't this cover what 'supports-clkreq' does?
>> Well, they are related partially. i.e. if a platform doesn't have 'supports-clkreq' set,
>> then, by definition, it can't advertise support for ASPM L1.1 and L1.2 states. But, ASPM-L0s
>> and ASPM-L1 states don't depend on 'supports-clkreq' property.
>> Having this property gives more granularity as to support for which particular ASPM state
>> shouldn't be advertised by the root port.
> 
> Okay, then it should be a common property then.
I'm planning to remove this given we have sysfs way (Heiner's patch series @
http://patchwork.ozlabs.org/project/linux-pci/list/?series=107392 to control which ASPM states
can be enabled run time. In case if that is not going to work for a given use case, I'll push
patches separately for controlling ASPM states advertisement/working.

> 
> Rob
>