<tero.kri...@nokia.com> writes: > > >>-----Original Message----- >>From: ext Kevin Hilman [mailto:khil...@deeprootsystems.com] >>Sent: 10 March, 2010 20:21 >>To: Kristo Tero (Nokia-D/Tampere) >>Cc: linux-omap@vger.kernel.org >>Subject: Re: [PATCHv6] OMAP3: Serial: Improved sleep logic >> >>Kevin Hilman <khil...@deeprootsystems.com> writes: >> >>> Tero Kristo <tero.kri...@nokia.com> writes: >>> >>>> From: Tero Kristo <tero.kri...@nokia.com> >>>> >>>> This patch contains following improvements: >>>> - Only RX interrupt will now kick the sleep prevent timer >>>> - TX fifo status is checked before disabling clocks, this >>will prevent >>>> on-going transmission to be cut >>>> - Smartidle is now enabled/disabled only while switching >>clocks, as having >>>> smartidle enabled while RX/TX prevents any wakeups from >>being received >>>> from UART module >>>> - Added workqueue for wakeup checks, as jiffy timer access >>within the >>>> idle loop results into skewed timers as jiffy timers are stopped >>>> - Added garbage_timer for ignoring the first character >>received during >>>> the first tick after clock enable, this prevents garbage >>characters to be >>>> received in low sleep states >>>> - omap_uart_enable_irqs() changed to use enable_irq / >>disable_irq instead >>>> of request / free. Using request/free changes the >>behavior after first >>>> suspend due to reversed interrupt handler ordering >>>> >>>> Signed-off-by: Tero Kristo <tero.kri...@nokia.com> >>> >>> Thanks Tero. This version looks good. >>> >>> Adding to pm-fixes queue for 2.6.34-rcX after minor change below... >>> >> >>There's still something slightly strange going on here... >> >>I noticed via powertop that the garbage timer is now one of the top >>reasons for wakeup in an idle system. Seems like the garbage timer >>is firing when it shouldn't be, and triggering unnecessary wakeups >> >>Based on powertop stats, the garbage timer is firing about 3x more >>often than the GPtimer that should be waking the system. > > You get one timer expire each wakeup cycle, but the system actually fires its > own timer for each UART, thus you get 3x. It is possible to optimize the > timer a bit by only firing it if we have a wakeup from UART, but this > probably causes occasional garbage to the console, if a wakeup from some > other source than UART and UART RX happen at the same time. Might be the > lesser of two evils though. > > I can experiment with this change a bit and see how it behaves. >
OK, the 3x makes sense, but the garbage timer should never be the cause of a wakeup. Maybe you also need to be sure that the garbage timer is disabled before clocks are disabled so it doesn't fire and cause a wakeup. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
