| Message ID | 1371739146-32639-4-git-send-email-f.fainelli@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Jun 20, 2013 at 03:39:06PM +0100, Florian Fainelli wrote: > ARM CPU device tree nodes may contain a "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 deduced the CPU capacity. The "clocks" > property, if present shall be a phandle to a valid clock node. > > Document thes properties to avoid any possible confusion on the > clock-frequency unit and also specify that "device_type" is also > used by the topology code. > > Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> > --- > Documentation/devicetree/bindings/arm/cpus.txt | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt > index f32494d..1ce1ace 100644 > --- a/Documentation/devicetree/bindings/arm/cpus.txt > +++ b/Documentation/devicetree/bindings/arm/cpus.txt > @@ -10,7 +10,7 @@ http://devicetree.org > > For the ARM architecture every CPU node must contain the following properties: > > -- device_type: must be "cpu" > +- device_type: must be "cpu". Use by the topology code. No. These are DT bindings, they are not related to kernel code and must be defined independently. > - reg: property matching the CPU MPIDR[23:0] register bits > reg[31:24] bits must be set to 0 > - compatible: should be one of: > @@ -45,6 +45,11 @@ For the ARM architecture every CPU node must contain the following properties: > "marvell,xsc3" > "marvell,xscale" > > +- clocks: phandle and clock specifier for the CPU clock, used if > + "device_type" is present. "device_type" must be present, no "if" there (see latest bindings that are on their way to the kernel) git://linux-arm.org/linux-2.6-lp.git dt-cpus-bindings Then we can see if a "clocks" property is suitable here, and try to understand what needs to happen when a platform has DVFS capabilities. I need to think more about this. > +- clock-frequency: the frequency of the CPU, in Hz. Mandatory if "device_type" > + is also present, used as fallback is "clocks" is not present. We should not define bindings to fix kernel code. Either "clock-frequency" is required or it is not, it should not depend on "device_type" being present and "device_type" is mandatory anyway. As I mentioned above, we still have to check how to handle multiple frequencies, and how to do it. I will give it more thought on my side. Lorenzo
2013/6/21 Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>: > On Thu, Jun 20, 2013 at 03:39:06PM +0100, Florian Fainelli wrote: >> ARM CPU device tree nodes may contain a "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 deduced the CPU capacity. The "clocks" >> property, if present shall be a phandle to a valid clock node. >> >> Document thes properties to avoid any possible confusion on the >> clock-frequency unit and also specify that "device_type" is also >> used by the topology code. >> >> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> >> --- >> Documentation/devicetree/bindings/arm/cpus.txt | 7 ++++++- >> 1 file changed, 6 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt >> index f32494d..1ce1ace 100644 >> --- a/Documentation/devicetree/bindings/arm/cpus.txt >> +++ b/Documentation/devicetree/bindings/arm/cpus.txt >> @@ -10,7 +10,7 @@ http://devicetree.org >> >> For the ARM architecture every CPU node must contain the following properties: >> >> -- device_type: must be "cpu" >> +- device_type: must be "cpu". Use by the topology code. > > No. These are DT bindings, they are not related to kernel code and must > be defined independently. Ok. > >> - reg: property matching the CPU MPIDR[23:0] register bits >> reg[31:24] bits must be set to 0 >> - compatible: should be one of: >> @@ -45,6 +45,11 @@ For the ARM architecture every CPU node must contain the following properties: >> "marvell,xsc3" >> "marvell,xscale" >> >> +- clocks: phandle and clock specifier for the CPU clock, used if >> + "device_type" is present. > > "device_type" must be present, no "if" there (see latest bindings that are on > their way to the kernel) > > git://linux-arm.org/linux-2.6-lp.git dt-cpus-bindings > > Then we can see if a "clocks" property is suitable here, and try to understand > what needs to happen when a platform has DVFS capabilities. I need to think > more about this. > >> +- clock-frequency: the frequency of the CPU, in Hz. Mandatory if "device_type" >> + is also present, used as fallback is "clocks" is not present. > We should not define bindings to fix kernel code. Either "clock-frequency" > is required or it is not, it should not depend on "device_type" being > present and "device_type" is mandatory anyway. As I mentioned above, we > still have to check how to handle multiple frequencies, and how to do it. > > I will give it more thought on my side. Sure. On the short term, I think it would be wise to clarify that "clock-frequency" must be in Hz so that people that define their binding now get it correctly.
diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt index f32494d..1ce1ace 100644 --- a/Documentation/devicetree/bindings/arm/cpus.txt +++ b/Documentation/devicetree/bindings/arm/cpus.txt @@ -10,7 +10,7 @@ http://devicetree.org For the ARM architecture every CPU node must contain the following properties: -- device_type: must be "cpu" +- device_type: must be "cpu". Use by the topology code. - reg: property matching the CPU MPIDR[23:0] register bits reg[31:24] bits must be set to 0 - compatible: should be one of: @@ -45,6 +45,11 @@ For the ARM architecture every CPU node must contain the following properties: "marvell,xsc3" "marvell,xscale" +- clocks: phandle and clock specifier for the CPU clock, used if + "device_type" is present. +- clock-frequency: the frequency of the CPU, in Hz. Mandatory if "device_type" + is also present, used as fallback is "clocks" is not present. + Example: cpus {
ARM CPU device tree nodes may contain a "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 deduced the CPU capacity. The "clocks" property, if present shall be a phandle to a valid clock node. Document thes properties to avoid any possible confusion on the clock-frequency unit and also specify that "device_type" is also used by the topology code. Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> --- Documentation/devicetree/bindings/arm/cpus.txt | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)