In Host PC that have USB Type C Ports is it correct to assume that they will be implemented with PD controllers and thus :-
Use the CC lines to decide whether to provide VBUS (and in the worse case may even not provide VBUS power) ?
Once proper validation with the device connected then will be able to provide +5V upto 3A on the VBUS lines ?
In Host PC that have USB Type C Ports is it correct to assume that they will be implemented with PD controllers
No, it is not correct to assume that every Type-C port uses PD - power delivery specifications. Power Delivery is independent and optional feature.
- Use the CC lines to decide whether to provide VBUS (and in the worse case may even not provide VBUS power) ?
This is the standard function of a Type-C port. No need for PD here.
- Once proper validation with the device connected then will be able to provide +5V upto 3A on the VBUS lines ?
Again, this is the standard function of a Type-C port, no Power Delivery is necessary. If the port carries the USB host function and is designed to drive up to 3 A power, it should "advertise" this capability by having 10k pullups on CC lines. If the port can source only 1.5 A, it should have 22k pull-up. If there is enough power only for 500 mA, the port should have 56k pull-up to 5V. A simple voltage comparator of device side is sufficient to determine source port power capability. The PD (or its subset) is required only if 5 A is designed in, or higher voltages are used.
A type C port can signal 5V power availability with the CC lines. The options are 3A, 1.5A, or legacy power. (Legacy power is 900mA for USB3, or 500mA for USB2...but you need to stick with 500 unless you're going to negotiate over the USB data lines.)
The primary reason for the CC line encoding is so that your phone can get a charge without negotiating over the data lines. Higher voltages and currents can be negotiated by a device with data capability, including the reverse--charging the laptop through its own USB port.
Although most type C ports are 3A, some aren't...some HP Zbooks, for example, erroneously advertise 1.5A but only supply 900mA.
In Host PC that have USB Type C Ports is it correct to assume that they will be implemented with PD controllers
It is up to manufacturer whether they support PD or not. Having said that, I suspect all new devices with Type C will support it.
Use the CC lines to decide whether to provide VBUS (and in the worse case may even not provide VBUS power)?
Since Type C is backwards compatible it has to provide at least 500mA for old devices without the use of CC lines. I don't know whether you can use CC to negotiate cutting yourself from any power. It makes little sense so I suspect designers did not even plan for this possibility.
UPDATE:
The above statement was based upon USB PD 3.0 specification. Following the comments by @AliChen I checked Type-C 1.3 specification. Apparently, Type-C ports implement "USB Type-C-specific implementation of the USB Power Delivery Specification". And later: "USB Power Delivery optimized for the USB Type-C connector".
Specifically, Type-C port does not supply 5V until it detects attached sink device and determines its type. So, yes, in worse case it may not provide VBUS (or VCONN) power.
Note that this behavior is allowed by PD spec, which states that downstream port can source either 5V or 0V in its initial state. I suspect that 0V option was added to PD 3.0 in a hurry to accommodate Type-C spec. First, because "source 0V" sounds idiotic, and second, because in some parts of the spec it still mentions only 5V and requires DFP to tolerate 5V supplied from the other side.
Once proper validation with the device connected then will be able to provide +5V upto 3A on the VBUS lines?
If you have port with PD 2.0 and up then yes. For PD 1.0 it's 2A. In either case "You're gonna need a bigger cable". But if you need more power you can try negotiate for 20V 5A, although it is my understanding the host may limit output power to whatever their circuitry can provide.
