"Mark A. Greer" <mgreer@xxxxxxxxxxxxxxx> writes: > On Tue, Apr 24, 2012 at 01:51:05PM -0700, Mark A. Greer wrote: >> On Wed, Apr 11, 2012 at 03:37:47PM -0600, Paul Walmsley wrote: >> > Hi >> >> Hi Paul, Kevin. >> >> > On Wed, 11 Apr 2012, Mark A. Greer wrote: >> > >> > > From: "Mark A. Greer" <mgreer@xxxxxxxxxxxxxxx> >> > > >> > > Currently, the OMAP3 cpuidle driver calls omap3_enter_idle() >> > > which calls omap_sram_idle(). omap_sram_idle() eventually >> > > causes a 'wfi' instruction to be executed effectively putting >> > > the system to sleep. It is assumed that an I/O wake-up event >> > > will occur to wake the system up again. This doesn't work on >> > > systems that don't support I/O wake-ups (indicated by >> > > omap3_has_io_wakeup() returning false). >> > > >> > > To handle this, follow the same path in omap3_enter_idle() >> > > that would be followed if an interrupt were pending. >> > >> > I don't quite understand this patch. Are you saying that AM3517/3505 >> > can't wake from WFI? That would seem odd. >> > >> > There are other sources of wakeup on the system other than I/O wakeup. >> > I/O wakeup only applies to wakeups from the I/O pads when the chip is in >> > RETENTION or OFF. And as I understand it, neither of those apply to >> > AM3517/3505? >> > >> > Even if I/O wakeups aren't supported, many of the IP blocks on the system >> > should be able to cause the ARM to exit WFI by asserting their >> > SWAKEUP lines and raising their interrupt lines. >> >> I have changed the code to keep everything in the ON state and use >> cpu_do_idle()--basically a wfi, cpu_v7_do_idle() in this case--and everything >> works well (except networking, see below) when using an mmc-based rootfs. >> >> The issue is with the emac--it can't wake the system up unless there >> is an irq from the PHY to a wakeup-enabled GPIO (confirmed by h/w engr). >> So, when using networking or using an nfs-based rootfs, there are all >> kinds of timeouts, etc. Basically, doing a wfi (i.e., pm_idle or cpuidle) >> and expecting the emac to wake the system back up won't work. >> >> How would you like me to proceed (to avoid the wfi in pm_idle & cpuidle)? > > Just thinking out loud... > > We could chose whether pm_idle & cpuidle issue a wfi based on > whether there is a davinci-emac present. The issue with that is > that someday there may be another SoC that has a davinci-emac that > can wake up the system. I know cpu_is_xxx() is frowned upon but > this does seem like a proper usage of it--the deciding factor > really is whether its an am35x or not (and CONFIG_TI_DAVINCI_EMAC > is enabled). The presence of the davinci_emac is probably overkill, avoiding WFI should really only be done when the davinci_emac is *active*. e.g. using an am35x with an EMAC *present*, but not in use because there's an MMC rootfs for example. If there's a good way to detect an in-use davinci_emac, then disable_hlt() can be used to avoid WFI. When the davinci_emac is not in use (e.g. module unloaded etc.) then enable_hlt() can be used to (re)allow WFI. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
