Re: [PATCH 11/11] ARM: tegra: pcie: Add device tree support

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On 03/08/2012 11:31 PM, Thierry Reding wrote:
> * Stephen Warren wrote:
>> On 03/08/2012 07:51 AM, Thierry Reding wrote:
>>> This commit adds support for instantiating the Tegra PCIe controller
>>> from a device tree.
>>>
>>> Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxxxxxxxxxx>
>>
>>> diff --git a/Documentation/devicetree/bindings/pci/tegra-pcie.txt b/Documentation/devicetree/bindings/pci/tegra-pcie.txt
>>
>>> +NVIDIA Tegra PCIe controller
>>> +
>>> +Required properties:
>>> +- compatible: "nvidia,tegra20-pcie"
>>> +- reg: physical base address and length of the controller's registers
>>> +- interrupts: the interrupt outputs of the controller
>>> +
>>> +Optional properties:
>>> +- pex-clk-supply: supply voltage for internal reference clock
>>> +- vdd-supply: power supply for controller (1.05V)
>>
>> Mark, Liam,
>>
>> Should those *-supply properties really be optional? I got the
>> impression talking to Mark in a different thread that all regulators
>> should exist, although their implementation may be via a fixed
>> regulator, with no GPIO, as determined by the board design.
> 
> If I read the TrimSlice code correctly, there is no regulator setup required
> to make PCIe work there presumably because they hardwire the proper voltages.

Yes. I believe that's exactly what the fixed regulator is for.

> On the other hand, maybe a better solution in this case would be to use the
> dummy regulator in those cases.

Mark indicated dummy regulators weren't the preferred mechanism:

http://lkml.org/lkml/2012/2/25/30
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