| Message ID | 1371635237-22860-1-git-send-email-f.fainelli@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jun 19, 2013 at 10:47:17AM +0100, Florian Fainelli wrote: > ARM CPU device tree nodes may contain an optional clock-frequency > property, when set, this property must contain the CPU frequency in Hz, > which is then used by the topology parsing code in > arch/arm/kernel/topology.c to infer the CPU capacity. I see that arch/arm/kernel/topology.c does a pr_err when clock-frequency isn't present. If we're documenting it as optional, should we not downgrade that or remove it entirely? Thanks, Mark. > > Document this property to avoid any possible confusion on the > clock-frequency unit. > > Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> > --- > Documentation/devicetree/bindings/arm/cpus.txt | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt > index f32494d..a33b956 100644 > --- a/Documentation/devicetree/bindings/arm/cpus.txt > +++ b/Documentation/devicetree/bindings/arm/cpus.txt > @@ -45,6 +45,8 @@ For the ARM architecture every CPU node must contain the following properties: > "marvell,xsc3" > "marvell,xscale" > > +- clock-frequency : The frequency of the CPU, in Hz. Optional. > + > Example: > > cpus { > -- > 1.8.1.2 > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
Hello Mark, 2013/6/19 Mark Rutland <mark.rutland@arm.com>: > On Wed, Jun 19, 2013 at 10:47:17AM +0100, Florian Fainelli wrote: >> ARM CPU device tree nodes may contain an optional clock-frequency >> property, when set, this property must contain the CPU frequency in Hz, >> which is then used by the topology parsing code in >> arch/arm/kernel/topology.c to infer the CPU capacity. > > I see that arch/arm/kernel/topology.c does a pr_err when clock-frequency isn't > present. If we're documenting it as optional, should we not downgrade that or > remove it entirely? Good question. I think it might be good to just dowgrade the error to a simple warning, we should clearly be fixing the binding if we have a device_type = "cpu" property but no clock-frequency property. -- Florian
On Wed, Jun 19, 2013 at 11:27:50AM +0100, Florian Fainelli wrote: > Hello Mark, > > 2013/6/19 Mark Rutland <mark.rutland@arm.com>: > > On Wed, Jun 19, 2013 at 10:47:17AM +0100, Florian Fainelli wrote: > >> ARM CPU device tree nodes may contain an optional clock-frequency > >> property, when set, this property must contain the CPU frequency in Hz, > >> which is then used by the topology parsing code in > >> arch/arm/kernel/topology.c to infer the CPU capacity. > > > > I see that arch/arm/kernel/topology.c does a pr_err when clock-frequency isn't > > present. If we're documenting it as optional, should we not downgrade that or > > remove it entirely? > > Good question. I think it might be good to just dowgrade the error to > a simple warning, we should clearly be fixing the binding if we have a > device_type = "cpu" property but no clock-frequency property. Well, this means that that pr_err will trigger as soon as the dts updates hit the mainline, now probably it is silent because cpu nodes for architectures with "arm,cortex-a15" as cpus miss device_type = "cpu". ePAPR defines "clock-frequency" as required. So either we downgrade it to optional or we are in for another slew of dts updates, I am really looking forward to that. Certainly it has to be added to the bindings. Thoughts ? Lorenzo
2013/6/19 Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>: > On Wed, Jun 19, 2013 at 11:27:50AM +0100, Florian Fainelli wrote: >> Hello Mark, >> >> 2013/6/19 Mark Rutland <mark.rutland@arm.com>: >> > On Wed, Jun 19, 2013 at 10:47:17AM +0100, Florian Fainelli wrote: >> >> ARM CPU device tree nodes may contain an optional clock-frequency >> >> property, when set, this property must contain the CPU frequency in Hz, >> >> which is then used by the topology parsing code in >> >> arch/arm/kernel/topology.c to infer the CPU capacity. >> > >> > I see that arch/arm/kernel/topology.c does a pr_err when clock-frequency isn't >> > present. If we're documenting it as optional, should we not downgrade that or >> > remove it entirely? >> >> Good question. I think it might be good to just dowgrade the error to >> a simple warning, we should clearly be fixing the binding if we have a >> device_type = "cpu" property but no clock-frequency property. > > Well, this means that that pr_err will trigger as soon as the dts > updates hit the mainline, now probably it is silent because cpu nodes > for architectures with "arm,cortex-a15" as cpus miss device_type = "cpu". > ePAPR defines "clock-frequency" as required. Correct. I am also fine with documenting this property as mandatory. > > So either we downgrade it to optional or we are in for another slew of dts > updates, I am really looking forward to that. Certainly it has to be added > to the bindings. > > Thoughts ? Well, the fix would be twofold: - for platforms which already have an "arm,cortex-a15" CPU nodes but lack a clock phandle or a clock-frequency add it - update arch/arm/kernel/toplogy.c to fetch the clock phandle and rate if specified (e.g: ecx-2000) Here is a list of platforms/DTS that would appear to need fixing: - exynos5440.dtsi - tegra114.dtsi - vexpress-v2p-ca15-tc1.dts - vexpress-v2p-ca15_a7.dts - xenvm-4.2.dts As far as I am concerned, the DTB passed to my kernel is already okay, but certainly this needs fixing for in-tree DTS files. -- Florian
diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt index f32494d..a33b956 100644 --- a/Documentation/devicetree/bindings/arm/cpus.txt +++ b/Documentation/devicetree/bindings/arm/cpus.txt @@ -45,6 +45,8 @@ For the ARM architecture every CPU node must contain the following properties: "marvell,xsc3" "marvell,xscale" +- clock-frequency : The frequency of the CPU, in Hz. Optional. + Example: cpus {
ARM CPU device tree nodes may contain an optional clock-frequency property, when set, this property must contain the CPU frequency in Hz, which is then used by the topology parsing code in arch/arm/kernel/topology.c to infer the CPU capacity. Document this property to avoid any possible confusion on the clock-frequency unit. Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> --- Documentation/devicetree/bindings/arm/cpus.txt | 2 ++ 1 file changed, 2 insertions(+)