On Tue, 12 Jul 2016, Dirk Behme wrote: > Clocks described by this property are reserved for use by Xen, and the OS > must not alter their state any way, such as disabling or gating a clock, > or modifying its rate. Ensuring this may impose constraints on parent > clocks or other resources used by the clock tree. > > This property is used to proxy clocks for devices Xen has taken ownership > of, such as UARTs, for which the associated clock controller(s) remain > under the control of Dom0. > > Up to now, the workaround for this has been to use the Linux kernel > command line parameter 'clk_ignore_unused'. See Xen bug > > http://bugs.xenproject.org/xen/bug/45 > > too. > > Signed-off-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx> > --- > Changes in v4: Switch to the xen.txt description proposed by Mark: > https://www.spinics.net/lists/arm-kernel/msg516158.html > > Changes in v3: Use the xen.txt description proposed by Michael. Thanks! > > Changes in v2: Drop the Linux implementation details like clk_disable_unused > in xen.txt. > > Documentation/devicetree/bindings/arm/xen.txt | 12 +++++++ > arch/arm/xen/enlighten.c | 47 +++++++++++++++++++++++++++ > 2 files changed, 59 insertions(+) > > diff --git a/Documentation/devicetree/bindings/arm/xen.txt b/Documentation/devicetree/bindings/arm/xen.txt > index c9b9321..437e50b 100644 > --- a/Documentation/devicetree/bindings/arm/xen.txt > +++ b/Documentation/devicetree/bindings/arm/xen.txt > @@ -17,6 +17,18 @@ the following properties: > A GIC node is also required. > This property is unnecessary when booting Dom0 using ACPI. > > +Optional properties: > + > +- clocks: a list of phandle + clock-specifier pairs > + Clocks described by this property are reserved for use by Xen, and the > + OS must not alter their state any way, such as disabling or gating a > + clock, or modifying its rate. Ensuring this may impose constraints on > + parent clocks or other resources used by the clock tree. > + > + Note: this property is used to proxy clocks for devices Xen has taken > + ownership of, such as UARTs, for which the associated clock > + controller(s) remain under the control of Dom0. > + > To support UEFI on Xen ARM virtual platforms, Xen populates the FDT "uefi" node > under /hypervisor with following parameters: > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c > index 47acb36..5c546d0 100644 > --- a/arch/arm/xen/enlighten.c > +++ b/arch/arm/xen/enlighten.c > @@ -24,6 +24,7 @@ > #include <linux/of_fdt.h> > #include <linux/of_irq.h> > #include <linux/of_address.h> > +#include <linux/clk-provider.h> > #include <linux/cpuidle.h> > #include <linux/cpufreq.h> > #include <linux/cpu.h> > @@ -444,6 +445,52 @@ static int __init xen_pm_init(void) > } > late_initcall(xen_pm_init); > > +/* > + * Check if we want to register some clocks, that they > + * are not freed because unused by clk_disable_unused(). > + * E.g. the serial console clock. > + */ > +static int __init xen_arm_register_clks(void) > +{ > + struct clk *clk; > + struct device_node *xen_node; > + unsigned int i, count; > + int ret = 0; > + > + xen_node = of_find_compatible_node(NULL, NULL, "xen,xen"); > + if (!xen_node) { > + pr_err("Xen support was detected before, but it has disappeared\n"); > + return -EINVAL; > + } Given that this is a late initcall, the following should work: if (!xen_domain()) return -ENODEV; -- 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
