On 10/2/19 4:45 AM, Nicolas Saenz Julienne wrote: > Currently, in arm_dt_init_cpu_maps(), the hwid of the boot CPU is read > from MPIDR on SMP devices and set to 0 for non SMP. This value is then > matched with the DT cpu nodes' reg property in order to find the boot > CPU in DT.
The code you change is about the "mpidr" variable, yet in your commit message you refer to "hwid", that is a tad confusing for the reader. > > On MP devices build without SMP the cpu DT node contains the expected > MPIDR yet the hwid is set to 0. With this the function fails to match > the cpus and uses the default CPU logical map. Making it impossible to > get the CPU's DT node further down the line. This causes issues with > cpufreq-dt, as it triggers warnings when not finding a suitable DT node > on CPU0. > > Change the way we choose whether to get MPIDR or not. Instead of > depending on SMP check the number of CPUs defined in DT. Anything > 1 > means MPIDR will be available. Except if someone accidentally wrote their Device Tree such as to have > 1 CPU nodes, yet the CPU is not MP capable and reading the MPIDR register does return the expected value, but that is wrong anyway. > > This was seen on a Raspberry Pi 2 build with bcm2835_defconfig. > > Reported-by: "kernelci.org bot" <[email protected]> > Signed-off-by: Nicolas Saenz Julienne <[email protected]> > --- > arch/arm/kernel/devtree.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c > index 39c978698406..a924fda9abc8 100644 > --- a/arch/arm/kernel/devtree.c > +++ b/arch/arm/kernel/devtree.c > @@ -74,7 +74,7 @@ void __init arm_dt_init_cpu_maps(void) > struct device_node *cpu, *cpus; > int found_method = 0; > u32 i, j, cpuidx = 1; > - u32 mpidr = is_smp() ? read_cpuid_mpidr() & MPIDR_HWID_BITMASK : 0; > + u32 mpidr = 0; > > u32 tmp_map[NR_CPUS] = { [0 ... NR_CPUS-1] = MPIDR_INVALID }; > bool bootcpu_valid = false; > @@ -83,6 +83,9 @@ void __init arm_dt_init_cpu_maps(void) > if (!cpus) > return; > > + if (is_smp() || of_get_child_count(cpus) > 1) > + mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK; > + > for_each_of_cpu_node(cpu) { > const __be32 *cell; > int prop_bytes; > -- Florian
