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    • Anton Vorontsov's avatar
      rtc: set wakeup capability for I2C and SPI RTC drivers · 26b3c01f
      Anton Vorontsov authored
      
      RTC core won't allow wakeup alarms to be set if RTC devices' parent (i.e.
      i2c_client or spi_device) isn't wakeup capable.
      
      For I2C devices there is I2C_CLIENT_WAKE flag exists that we can pass via
      board info, and if set, I2C core will initialize wakeup capability.  For
      SPI devices there is no such flag at all.
      
      I believe that it's not platform code responsibility to allow or disallow
      wakeups, instead, drivers themselves should set the capability if a device
      can trigger wakeups.
      
      That's what drivers/base/power/sysfs.c says:
      
       * It is the responsibility of device drivers to enable (or disable)
       * wakeup signaling as part of changing device power states, respecting
       * the policy choices provided through the driver model.
      
      I2C and SPI RTC devices send wakeup events via interrupt lines, so we
      should set the wakeup capability if IRQ is routed.
      
      Ideally we should also check irq for wakeup capability before setting
      device's capability, i.e.
      
      	if (can_irq_wake(irq))
      		device_set_wakeup_capable(&client->dev, 1);
      
      But there is no can_irq_wake() call exist, and it is not that trivial to
      implement it for all interrupts controllers and complex/cascaded setups.
      
      drivers/base/power/sysfs.c also covers these cases:
      
       * Devices may not be able to generate wakeup events from all power
       * states.  Also, the events may be ignored in some configurations;
       * for example, they might need help from other devices that aren't
       * active
      
      So there is no guarantee that wakeup will actually work, and so I think
      there is no point in being pedantic wrt checking IRQ wakeup capability.
      
      Signed-off-by: default avatarAnton Vorontsov <avorontsov@ru.mvista.com>
      Cc: David Brownell <dbrownell@users.sourceforge.net>
      Cc: Ben Dooks <ben-linux@fluff.org>
      Cc: Jean Delvare <khali@linux-fr.org>
      Cc: Alessandro Zummo <a.zummo@towertech.it>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      26b3c01f
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