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

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Date:   Sat, 12 Nov 2016 12:40:10 +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>
Subject: Re: [PATCH 3/4] PCI: dra7xx: Add support to force RC to work in GEN1
 mode

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?

Thanks
Kishon