On 13-02-2019 18:46, Thierry Reding wrote:
> On Wed, Feb 13, 2019 at 01:56:24PM +0100, Thierry Reding wrote:
>> On Wed, Feb 13, 2019 at 04:08:15PM +0530, Nagarjuna Kristam wrote:
>>>
>>>
>>> On 04-02-2019 17:18, Thierry Reding wrote:
>>>> On Thu, Jan 03, 2019 at 03:34:54PM +0530, Nagarjuna Kristam wrote:
>>>>> Add binding details regarding nvidia,usb3-port-fake
>>>>>
>>>>> Signed-off-by: Nagarjuna Kristam <nkristam@xxxxxxxxxx>
>>>>> ---
>>>>> Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt | 3 +++
>>>>> 1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
>>>>> index 3742c15..21a5541 100644
>>>>> --- a/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
>>>>> +++ b/Documentation/devicetree/bindings/phy/nvidia,tegra124-xusb-padctl.txt
>>>>> @@ -158,6 +158,9 @@ Optional properties:
>>>>> is internal. In the absence of this property the port is considered to be
>>>>> external.
>>>>> - vbus-supply: phandle to a regulator supplying the VBUS voltage.
>>>>> +- nvidia,usb3-port-fake: A integer property whose presense informs that a
>>>>> + fake USB3 port needs to be mapped for corresponding USB2 port. This entry
>>>>> + is applicable only for Tegra210 based platforms which has USB2 only ports.
>>>>
>>>> You don't provide a rationale fo why this fake USB3 port needs to be
>>>> specified. Doesn't the OTG port work without the fake USB3 port? Why
>>>> does it need to be specified and which one should be used as fake?
>>>>
>>>
>>> Yes, on Tegra210 based platforms, USB2 only device/OTG ports don't work
>>>
>>>> You mention elsewhere that an unused USB3 port is used on Jetson TX1,
>>>> but what if there are no unused ports on a platform? Can we use any
>>>> USB3 port for this purpose?
>>>>
>>>
>>> If we dont have any unused port, we cannot get device mode working on USB2 only port.
>>> We cannot use any USB3 port, we need to use an un-used USB3 port, so that we can
>>> fake that corresponding USB2 only port as USB2 and USB3 port.
>>
>> Hm... seems to me like we should be able to do this without an extra
>> device tree property. Surely we can determine at runtime which of the
>> ports are actually unused and pick one? If it doesn't matter which one,
>> we can just pick the first one that's unused, or an unused one at
>> random.
>
> It's slightly more complicated than I thought because there's an
> optimization in tegra_xusb_add_usb3_port() that will cause only used
> ports to get registered. But I think we can do something like this
> (untested) to get hold of an unused one, since we only need the index
> of the port:
>
> static int tegra_xusb_find_unused_usb3_port(struct tegra_xusb_padctl *padctl)
> {
> struct device_node *np;
> unsigned int i;
>
> for (i = 0; i < padctl->soc->ports.usb3.count; i++) {
> np = tegra_xusb_find_port_node(padctl, "usb3", i);
> if (!np || !of_device_is_available(np))
> return index;
> }
>
> return -ENODEV;
> }
>
> Thierry
>
It not just about un-used USB3 port, we need to find which usb2 port is registered as
otg/device and then check if it doesnot have any companion usb3 port. On this condition
we need to assign unused usb3 port as fake port.
Above is possible, however port_fake need is must for T210 and only for device mode operation
and not for other SOC or USB mode.
So shall i place SOC data(tegra210_xusb_padctl_soc) to read if port fake is needed ?
If yes, and no un-used port available, will mark case as warning(not error) and make probe(tegra_xusb_padctl_probe)
success irrespective of this. Since port can be otg but can be designed to use only for Host mode.
I am not sure if above complication is better than an dt entry.
Please share your info.
- Nagarjuna
