Am Sonntag, den 30.03.2014, 19:36 +0200 schrieb Marek Vasut: > On Friday, March 28, 2014 at 05:52:53 PM, Lucas Stach wrote: > > The glue around the core designware IP is significantly > > different between the Exynos and i.MX implementation, > > which is reflected in the DT bindings. > > > > This changes the i.MX6 binding to reuse as much as > > possible from the common designware binding and > > removes old cruft. > > > > I removed the optional GPIOs with the following reasoning: > > - disable-gpio: endpoint specific GPIO, not currently > > wired up in any code. Should be handled by the PCI device > > driver, not the host controller driver. > > - wake-up-gpio: same as above. > > - power-on-gpio: No user in any upstream DT. This should > > be handled by a regulator which shouldn't be controlled > > by the host driver, but rather by the PCI device driver. > > This power-on-gpio should indeed be handled by the regulator, but the regulator > cannot be handled by the PCIe device driver. This power-on-gpio must be operated > on per-slot basis if I understand it correctly, so it cannot be controlled by > the host controller driver either. > > The reason why this cannot be controlled by the device driver is that if the > device is powered down, it won't be detected on the PCIe bus, thus it cannot > enable the regulator which will power up the slot the device is sitting in. > So we are on the same page with regard to a GPIO being the wrong abstraction for this, I think. For the regulator part I would argue that PCI is a bus that is built around the ability to inspect the bus and detect devices on the bus at probe time, so any regulator that's powering a PCI device should be boot-on. Only after the device driver is loaded it should be able to fetch the regulator to power down/up the device as it wishes. In the x86 world this is AFAIK done using ACPI methods. I think the host controller driver has no business in controlling the device power, more so as there possibly could be a lot of devices on the bus even with a single host lane. > > btw. am I blind or do I just not see devicetree-discuss on CC ? > Hm, there is devicetree@xxxxxxxxxxxxxxx on CC, which MAINTAINER says is the right list for this stuff. Regards, Lucas -- Pengutronix e.K. | Lucas Stach | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-5076 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
