Hi Tim, Am Montag, den 21.12.2015, 13:05 -0800 schrieb Tim Harvey: > Lucas / Shawn / Sean, > > Do any of you know what should be done in order to use the LVDS2 > clock > as an 'input' for IMX6 PCIe? > > Due to the fact that Freescale's internal clock does not pass Gen2 > jitter tests, we have designed an IMX6 based board that follows > Freescale's recommendation to use an external Gen2 compliant clockgen > running to one of the LVDS clocks and now need to configure the > kernel > to use this as an input. I had this run to LVDS2 because LVDS1 is > configured by the kernel as a clock output for all IMX6 (see > 74b8031307c5d33d36742c26dd0921991bd5a255). > > My understanding is that if nothing is changed the host controller > would use its internal reference clock, and the PCIe socket would use > the external clkgen and all would be well and fine for Gen1 because > they don't need to have synchronized clocks, but if Gen2 is needed we > must change the clock routing such that LVDS2 is an input and that it > is routed to the PCIe host controller reference clock. > > I know that I can use IMX6QDL_CLK_LVDS2_IN instead of > IMX6QDL_CLK_LVDS1_GATE in the clocks property of the PCIe node in the > device-tree to configure LVDS2 as an input instead of LVDS1 as an > output, but I'm not sure what to do with the rest of the clock tree > and how to handle this dynamically at runtime. > > Any ideas would be greatly appreciated. > What you would need to do is the following, I think: 1. Overwrite the PCIe node clocks property in your board as described above. 2. Set up the right connections in the clock tree by using the "assigned-clocks" property attached to the PCIe node. This might need some additions to the imx6 clock controller so you can attach the external clockgen (abstracted as fixed-clock) as a parent to the IMX6QDL_CLK_LVDS2_IN. Regards, Lucas -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
