Re: [PATCH v4 3/4] dt-bindings: phy: Add support for QMP phy

From: Vivek Gautam
Date: Tue Jan 24 2017 - 09:05:59 EST

On Tue, Jan 24, 2017 at 3:03 PM, Kishon Vijay Abraham I <kishon@xxxxxx> wrote:
> Hi,
> On Friday 20 January 2017 03:12 AM, Stephen Boyd wrote:
>> On 01/19, Vivek Gautam wrote:
>>> On 01/19/2017 06:10 AM, Stephen Boyd wrote:
>>>> Didn't we already move away from subnodes for lanes in an earlier
>>>> revision of these patches? I seem to recall we did that because
>>>> lanes are not devices and the whole "phy as a bus" concept not
>>>> making sense.
>>> Yea, we started out without having any sub-nodes and we
>>> argued that we don't require them since the qmp device is
>>> represented by the qmp node itself.
>>> The lanes otoh are representative of gen_phys and related properties.
>>> In the driver -
>>> "struct qmp_phy " represents the lanes and holds "struct phy",
>>> "struct qcom_qmp" represents the qmp block as a whole and holds
>>> "struct device"
>>> Does this make lanes qualify to be childs of qmp ?
>> Hmm... maybe I was recalling the DSI phy binding. I think there
>> are lanes there too but we decided to just have one node.
>>> "phy as a bus" (just trying to understand here) -
>>> let's say a usb phy controller has one HSIC phy port and one USB2 phy port.
>>> So, should this phy controller be a bus providing two ports (and so
>>> we will have
>>> couple of child nodes to the phy controller) ?
>> Typically in DT a subnode or collection of subnodes means there's
>> some sort of bus involved. Usually each node corresponds to a
>> struct device, and the parent node corresponds to the bus or
>> controller for the logical bus.
>> In this case (only PCIe though? not UFS or USB?) it seems like we
>> have multiple phys that share a common register space, but
>> otherwise they have their own register space and power
>> management. Would you have each PCIe controller point to a
>> different subnode for their associated phy? I'm trying to
>> understand the benefit of the subnodes if they aren't treated as
>> struct devices.
> Yes, instead of having all the controller having a phandle to the same PHY and
> then using other mechanisms to differentiate between the PHYs, each controller
> can have a phandle to the exact port that it is connected to.
> This also gives a better representation of the hardware and can avoid lot of
> boilerplate code in the driver.

Below is one binding that works for me.
phy@34000 {
compatible = "qcom,msm8996-qmp-pcie-phy";
reg = <0x034000 0x488>;
#clock-cells = <1>;
#address-cells = <1>;
#size-cells = <1>;

clocks = <&gcc GCC_PCIE_PHY_AUX_CLK>,
clock-names = "aux", "cfg_ahb", "ref";

vdda-phy-supply = <&pm8994_l28>;
vdda-pll-supply = <&pm8994_l12>;

resets = <&gcc GCC_PCIE_PHY_BCR>,
reset-names = "phy", "common", "cfg";

pciephy_p0: port@0 {
reg = <0x035000 0x130>,
<0x035200 0x200>,
<0x035400 0x1dc>;
#phy-cells = <0>;

clocks = <&gcc GCC_PCIE_0_PIPE_CLK>;
clock-names = "pipe0";
resets = <&gcc GCC_PCIE_0_PHY_BCR>;
reset-names = "lane0";

pciephy_p1: port@1 {
reg = <0x036000 0x130>,
<0x036200 0x200>,
<0x036400 0x1dc>;
#phy-cells = <0>;

clocks = <&gcc GCC_PCIE_1_PIPE_CLK>;
clock-names = "pipe1";
resets = <&gcc GCC_PCIE_1_PHY_BCR>;
reset-names = "lane1";

pciephy_p2: port@2 {
reg = <0x037000 0x130>,
<0x037200 0x200>,
<0x037400 0x1dc>;
#phy-cells = <0>;

clocks = <&gcc GCC_PCIE_2_PIPE_CLK>;
clock-names = "pipe2";
resets = <&gcc GCC_PCIE_2_PHY_BCR>;
reset-names = "lane2";

let me know if this looks okay.


> Thanks
> Kishon
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