[PATCH v2 1/2] ARM: topology: Use a clock if possible to get the CPU frequency

[Vincent Guittot]

On 30 June 2014 14:49, Maxime Ripard <maxime.ripard at free-electrons.com> wrote:
> On Mon, Jun 30, 2014 at 12:39:26PM +0200, Vincent Guittot wrote:
>> On 30 June 2014 12:29, Russell King - ARM Linux <linux at arm.linux.org.uk> wrote:
>> > On Mon, Jun 30, 2014 at 12:12:22PM +0200, Maxime Ripard wrote:
>> >> The Cortex-A7 and Cortex-A15 based SoCs need a clock-frequency property in the
>> >> topology code.
>> >>
>> >> Allow to use a clock to provide the same information.
>> >>
>> >> Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>
>> >
>> > This looks fine to me, but I don't know this code.  Maybe Vincent Guittot
>> > should be on the To: list (added)?
>>
>> Thanks
>
> Ah, sorry for that.
>
>>
>> >
>> >> ---
>> >>  arch/arm/kernel/topology.c | 25 ++++++++++++++++++-------
>> >>  1 file changed, 18 insertions(+), 7 deletions(-)
>> >>
>> >> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
>> >> index 9d853189028b..268443d88094 100644
>> >> --- a/arch/arm/kernel/topology.c
>> >> +++ b/arch/arm/kernel/topology.c
>> >> @@ -11,6 +11,7 @@
>> >>   * for more details.
>> >>   */
>> >>
>> >> +#include <linux/clk.h>
>> >>  #include <linux/cpu.h>
>> >>  #include <linux/cpumask.h>
>> >>  #include <linux/export.h>
>> >> @@ -100,8 +101,8 @@ static void __init parse_dt_topology(void)
>> >>                                GFP_NOWAIT);
>> >>
>> >>       for_each_possible_cpu(cpu) {
>> >> -             const u32 *rate;
>> >> -             int len;
>> >> +             struct clk *clk;
>> >> +             u32 rate = 0;
>> >>
>> >>               /* too early to use cpu->of_node */
>> >>               cn = of_get_cpu_node(cpu, NULL);
>> >> @@ -117,14 +118,24 @@ static void __init parse_dt_topology(void)
>> >>               if (cpu_eff->compatible == NULL)
>> >>                       continue;
>> >>
>> >> -             rate = of_get_property(cn, "clock-frequency", &len);
>> >> -             if (!rate || len != 4) {
>> >> -                     pr_err("%s missing clock-frequency property\n",
>> >> -                             cn->full_name);
>> >> +             clk = of_clk_get(cn, 0);
>> >> +             if (!IS_ERR(clk))
>> >> +                     rate = clk_get_rate(clk);
>>
>> We need the max frequency as it will be used to weight the different
>> CPUs capacity. How do you ensure that the current clock rate is the
>> max one ?
>
> Hmm, the clock-frequency attribute in the ePAPR is defined at the
> current CPU frequency, not the max one.

What means current frequency in device tree when DVFS is involved ?

Vincent

>
> Maxime
>
> --
> Maxime Ripard, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com