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    ARM: OMAP2+: omap_device: call all suspend, resume callbacks when... · b7c39a3f
    Paul Walmsley authored
    ARM: OMAP2+: omap_device: call all suspend, resume callbacks when OMAP_DEVICE_NO_IDLE_ON_SUSPEND is set
    
    During system suspend, when OMAP_DEVICE_NO_IDLE_ON_SUSPEND is set on
    an omap_device, call the corresponding driver's ->suspend() and
    ->suspend_noirq() callbacks (if present).  Similarly, during resume,
    the driver's ->resume() and ->resume_noirq() callbacks must both be
    called, if present.  (The previous code only called ->suspend_noirq()
    and ->resume_noirq().)
    
    If all of these callbacks aren't called, some important driver
    suspend/resume code may not get executed.
    
    In current mainline, the bug fixed by this patch is only a problem
    under the following conditions:
    
    - the kernel is running on an OMAP4
    
    - an OMAP UART is used as a console
    
    - the kernel command line parameter 'no_console_suspend' is specified
    
    - and the system enters suspend ("echo mem > /sys/power/state").
    
    Under this combined circumstance, the system cannot be awakened via
    the serial port after commit be4b0281c
    ("tty: serial: OMAP: block idle while the UART is transferring data in
    PIO mode").  This is because the OMAP UART driver's ->suspend()
    callback is never called.  The ->suspend() callback would have called
    uart_suspend_port() which in turn would call enable_irq_wake().  Since
    enable_irq_wake() isn't called for the UART's IRQ, check_wakeup_irqs()
    would mask off the UART IRQ in the GIC.
    
    On v3.3 kernels prior to the above commit, serial resume from suspend
    presumably occurred via the PRCM interrupt.  The UART was in
    smart-idle mode, so it was able to send a PRCM wakeup which in turn
    would be converted into a PRCM interrupt to the GIC, waking up the
    kernel.  But after the above commit, when the system is suspended in
    the middle of a UART transmit, the UART IP block would be in no-idle
    mode.  In no-idle mode, the UART won't generate wakeups to the PRCM
    when incoming characters are received; only GIC interrupts.  But since
    the UART driver's ->suspend() callback is never called,
    uart_suspend_port() and enable_irq_wake() is never called; so the UART
    interrupt is masked by check_wakeup_irqs() and the UART can't wake up
    the MPU.
    
    The remaining mechanism that could have awakened the system would have
    been I/O chain wakeups.  These wouldn't be active because the console
    UART's clocks are never disabled when no_console_suspend is used,
    preventing the full chip from idling.  Also, current mainline doesn't
    yet support full chip idle states for OMAP4, so I/O chain wakeups are
    not enabled.
    
    This patch is the result of a collaboration.  John Stultz
    <johnstul@us.ibm.com> and Andy Green <andy.green@linaro.org> reported
    the serial wakeup problem that led to the discovery of this problem.
    Kevin Hilman <khilman@ti.com> narrowed the problem down to the use of
    no_console_suspend.
    Signed-off-by: default avatarPaul Walmsley <paul@pwsan.com>
    Cc: John Stultz <johnstul@us.ibm.com>
    Cc: Andy Green <andy.green@linaro.org>
    Reviewed-by: default avatarKevin Hilman <khilman@ti.com>
    Signed-off-by: default avatarKevin Hilman <khilman@ti.com>
    b7c39a3f
omap_device.c 30.6 KB