Re: [PATCH] PM / OPP: Don't check not plugged in CPUs to avoid error

[Stephen Boyd <sboyd@codeaurora.org>]

On 07/13, Waldemar Rymarkiewicz wrote:
> On systems where not all possible CPUs are available for Linux call to
> dev_pm_opp_of_get_sharing_cpus() will fail as cannot find a cpu device
> for not present (not available) CPUs.
> 
> Example (real use case):
> 2 physical MIPS cores, 4 VPE, cpu0/2 run Linux and cpu1/3 are not available
> for linux. cpufreq-dt driver + opp v2 fail to register opp_table due to the
> fact there is no struct device for cpu1 (cpu1 not available for Linux).
> 
> Solve the problem by iterating over cpu_present_mask instead of
> cpu_possible_mask.
> 
> Signed-off-by: Waldemar Rymarkiewicz <waldemarx.rymarkiewicz@intel.com>

Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>

> ---
>  drivers/base/power/opp/of.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/power/opp/of.c b/drivers/base/power/opp/of.c
> index 57eec1c..389c924 100644
> --- a/drivers/base/power/opp/of.c
> +++ b/drivers/base/power/opp/of.c
> @@ -589,7 +589,7 @@ int dev_pm_opp_of_get_sharing_cpus(struct device *cpu_dev,
>  	if (!of_property_read_bool(np, "opp-shared"))
>  		goto put_cpu_node;
>  
> -	for_each_possible_cpu(cpu) {
> +	for_each_present_cpu(cpu) {
>  		if (cpu == cpu_dev->id)
>  			continue;
>  

Is there some way to iterate through all cpu nodes in DT without
using devices? I suppose some sort of loop on top of
of_get_cpu_node().

I worry that we may have some problem where we want to know about
all the CPUs that are sharing a particular OPP table but they
haven't been physically hotplugged yet. This also raises the
question about what the DT looks like before and after a CPU is
inserted into a system. If the non-present CPU nodes are in DT
all the time, then it may make sense for cpufreq-dt to intersect
the OPP sharing mask with the cpu_present_mask.

Probably nobody cares about knowing this difference though,
because we pretty much forward the result to cpufreq, so moving
to the present mask is good enough.

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