linux-kernel - Re: [PATCH 3/4] PCI: dra7xx: Add support to force RC to work in GEN1 mode

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Date:   Wed, 16 Nov 2016 22:14:00 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>, <linux-omap@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <nsekhar@...com>,
        Shawn Lin <shawn.lin@...k-chips.com>
Subject: Re: [PATCH 3/4] PCI: dra7xx: Add support to force RC to work in GEN1
 mode

Hi Bjorn,

On Tuesday 15 November 2016 02:54 AM, Bjorn Helgaas wrote:
> [+cc Shawn]
> 
> On Sat, Nov 12, 2016 at 12:40:10PM +0530, Kishon Vijay Abraham I wrote:
>> Hi,
>>
>> On Saturday 12 November 2016 02:45 AM, Bjorn Helgaas wrote:
>>> Hi Kishon,
>>>
>>> On Tue, Oct 11, 2016 at 06:28:34PM +0530, Kishon Vijay Abraham I wrote:
>>>> PCIe in AM57x/DRA7x devices is by default
>>>> configured to work in GEN2 mode.  However there
>>>> may be situations when working in GEN1 mode is
>>>> desired. One example is limitation i925 (PCIe GEN2
>>>> mode not supported at junction temperatures < 0C).
>>>>
>>>> Add support to force Root Complex to work in GEN1
>>>> mode if so desired, but don't force GEN1 mode on
>>>> any board just yet.
>>>>
>>>> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
>>>> Signed-off-by: Sekhar Nori <nsekhar@...com>
>>>> ---
>>>>  Documentation/devicetree/bindings/pci/ti-pci.txt |    1 +
>>>>  drivers/pci/host/pci-dra7xx.c                    |   27 ++++++++++++++++++++++
>>>>  2 files changed, 28 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/pci/ti-pci.txt b/Documentation/devicetree/bindings/pci/ti-pci.txt
>>>> index 60e2516..a3d6ca3 100644
>>>> --- a/Documentation/devicetree/bindings/pci/ti-pci.txt
>>>> +++ b/Documentation/devicetree/bindings/pci/ti-pci.txt
>>>> @@ -25,6 +25,7 @@ PCIe Designware Controller
>>>>  
>>>>  Optional Property:
>>>>   - gpios : Should be added if a gpio line is required to drive PERST# line
>>>> + - ti,pcie-is-gen1 : Force the PCIe controller to work in GEN1 (2.5 GT/s).
>>>
>>> Can we use "max-link-speed" so it's similar to imx6?
>>
>> yeah, maybe we should make it a generic PCI property?
> 
> I forgot that Shawn has already done this!  I had already merged those
> patches on pci/host-rockchip, but I moved them to pci/host since
> they're not Rockchip-specific.  Can you take a look at that and see if
> you can do what you need based on that pci/host branch?

Sure, I'll look at that on Monday when I'm back from vacation.

Cheers
Kishon