• Stephen Boyd's avatar
    ARM: 6993/1: platsmp: Allow secondary cpu hotplug with maxcpus=1 · 7fa22bd5
    Stephen Boyd authored
    If an ARM system has multiple cpus in the same socket and the
    kernel is booted with maxcpus=1, secondary cpus are possible but
    not present due to how platform_smp_prepare_cpus() is called.
    Since most typical ARM processors don't actually support physical
    hotplug, initialize the present map to be equal to the possible
    map in generic ARM SMP code. Also, always call
    platform_smp_prepare_cpus() as long as max_cpus is non-zero (0
    means no SMP) to allow platform code to do any SMP setup.
    
    After applying this patch it's possible to boot an ARM system
    with maxcpus=1 on the command line and then hotplug in secondary
    cpus via sysfs. This is more in line with how x86 does things.
    Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
    Cc: Paul Mundt <lethal@linux-sh.org>
    Cc: Kukjin Kim <kgene.kim@samsung.com>
    Cc: David Brown <davidb@codeaurora.org>
    Cc: Tony Lindgren <tony@atomide.com>
    Cc: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
    Cc: Linus Walleij <linus.walleij@stericsson.com>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    7fa22bd5
platsmp.c 4.31 KB