lkml.org 
[lkml]   [2019]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC 0/2] Add workaround for core wake-up on IPI for i.MX8MQ
    On Wed, 12 Jun 2019 08:14:16 +0100,
    Thomas Gleixner <tglx@linutronix.de> wrote:
    > On Mon, 10 Jun 2019, Leonard Crestez wrote:
    > > On 6/10/2019 5:08 PM, Marc Zyngier wrote:
    > > > Nobody is talking about performance here. It is strictly about
    > > > correctness, and what I read about this system is that it cannot
    > > > reliably use cpuidle.
    > > My argument was that it's fine if PPIs and LPIs are broken as long as
    > > they're not used:
    > >
    > > * PPIs are only used for local timer which is not used for wakeup.
    >
    > Huch? The timer has to bring the CPU out of idle as any other
    > interrupt.

    They use a separate hack for that, pretending that the timer is
    stopped during idle (it isn't), and setup a broadcast timer when
    entering idle. That timer uses an interrupt that can wake-up the
    target CPU, and all is well in the world. Sort of.

    Of course, this breaks as PPIs are not only used by the timer, but
    also by a number of other HW bits (PMU, GIC, guest and hypervisor
    timers), and they don't have corresponding hacks to back them up.

    Thanks,

    M.

    --
    Jazz is not dead, it just smells funny.

    \
     
     \ /
      Last update: 2019-06-12 09:37    [W:3.493 / U:0.036 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site