On Tuesday 04 March 2014, Lucas Stach wrote: > > > On i.MX6 the clock names (which I have to agree are pretty bad) map as > > > follows: > > > pcie_axi: host controller main register/bus access clock > > > pcie_ref_125m: pcie phy reference clock > > > > > > sata_ref_100m: pcie bus 100MHz reference clock > > > > That doesn't explain why it's called "sata_ref_100m". > > > I agree this is bad naming. It's called this way because someone decided > to name it like the internal clock it is sourced from on most boards. > This really should be pcie_ref, or something. I suspect this corresponds > to the pcie_bus clock in the Exynos binding in which case we should just > name it this way. Ok, so Exynos is missing one of the other clocks then? Or is the pcie_ref_125m clock something that should actually be listed under the node of the PHY? > > > lvds_gate: bad abstraction. Decides if the reference clock is sourced > > > internal (i.e. the 100MHz ref clock above) or from an SoC external > > > source. We should really find a better way of representing this in the > > > clock tree. > > > > I don't understand this description at all. Can you try to explain that > > with different words? > > > On i.MX6 the PCIe reference clock is routed through a generic clock pad, > which can be configured either as input or output. When the i.MX is the > PCI master we source the clock from sata_ref_100m and configure this pad > as clock output. > Somebody decided to abstract the input/output switch as a gate, which is > arguably wrong, this should be a mux deciding between internal or > external clock source. > > The PCIe host driver should really only need the clk pad clock, > activation of the sata_ref_100m clock should be handled through > parent<->child relationship of those clocks in the clock tree, which > isn't properly handled right now. I'll try to fix this up, but it won't > be backward compatible in any way. Is it possible to treat this clock as a "global" clock rather than a device specific one, and pass NULL as the device for clk_get? That's not nice, but at least it gives you a way to keep it out of the binding, and "just" creates a dependency between the specific PCI host controller and the way that clock is wired up on a particular SoC. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
