On Thu, 17 Mar 2016, Linus Walleij linus.walleij@linaro.org wrote:
On Wed, Mar 16, 2016 at 2:34 PM, Daniel Vetter daniel@ffwll.ch wrote:
On Wed, Mar 16, 2016 at 01:27:49PM +0100, Linus Walleij wrote:
- What is a HPD interrupt?
hotplug interrupt, fires when you plug in a cable.
- What is a Type-C DP HPD?
usb type C connector can multiplex both DisplayPort and USB, you need to renegotiate the lane splitting every time the sink changes, i.e. on each hotplug.
OK I understand, thanks a lot!
- Again why can't you just use a notifier or function call?
Because windows sucks, hence all that coordination happens through hw forwarded interrupts and magic registers. Same horror story on the sound side, where the sound driver needs to know what kind of PCM stream the monitor can take. It's hilarious. Except when they screw up the design and then need to fake parts of it in software.
So the story is something like that these IRQs have been put into hardware in order to compensate for flaws in Windows device driver model, I see.
If there are such special registers in some hardware I guess I'm all for implementing some generic quirk in gpiolib for people who need to software-trigger GPIO IRQs. Could be good for testing too, as there are such registers in ARMs PL061 GPIO controller for test, just so as to simulate a GPIO IRQ.
gpiod_trig_irq() would work with me, I'm happy to support whatever the GPIO hardware can do usually.
In sound we've switched over to a proper sw interface, and we tie the different parts (drm graphics driver and alsa snd driver) using the component.c framework.
Hm is that solution or something similar proper for USB connector as well I wonder... I was thinking about just adding $random_notifier but maybe that is a bit ugly :/
What is VPG? Now it seems Intel's internal organization is being used as part of the argument to get this change in and that makes me a bit annoyed.
(...)
There was chat of usb type C support for forever, but I was always promised that we don't need any interactions on the sw side and it's all magic in hw. There hasn't been any real design discussions in the open source group. VPG is the hw/windows group and generally comes up with "interesting" designs not suitable for upstream.
Feel free to just nack this stuff, and please cc intel-gfx/dri-devel in the future (since I tend to ignore everything that's not cc'ed to mailing lists I don't care about, even when I'm on cc personally). I've added them all to cc.
Thanks a lot Daniel, I understand better now. I'm not really against adding this "interesting" workaround if that is how Windows works, we usually have to go by their standards. From the GPIO point of view it is OK, just something the GPIO can do. I would be more worried about what the USB PHY maintainer (Felipe) is going to say about this.
Adding Felipe's current address. Considering the new domain part of the address, I'm hopeful we can sort this out. ;)
BR, Jani.
Yours, Linus Walleij _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx