> -----Original Message----- > From: linux-omap-ow...@vger.kernel.org [mailto:linux-omap- > ow...@vger.kernel.org] On Behalf Of Kevin Hilman > Sent: Monday, August 09, 2010 9:01 PM > To: Basak, Partha > Cc: Paul Walmsley; linux-omap@vger.kernel.org; Kalliguddi, Hema; Raja, > Govindraj; Varadarajan, Charulatha > Subject: Re: Issues with calling pm_runtime functions in > platform_pm_suspend_noirq/IRQ disabled context. > > "Basak, Partha" <p-bas...@ti.com> writes: > > >> Finally, we have omap_sram_idle(): > >> > >> > In particular, for USB, while executing SRAM_Idle, is we use > pm_runtime > >> > functions, we see spurious IO-Pad interrupts. > >> > >> Your message doesn't specify what PM runtime functions you are > executing. > >> But if those functions are calling mutex_lock(), then they obviously > must > >> not be called from omap_sram_idle() in interrupt context. > >> > >> It's not clear from your message why you need to call PM runtime > functions > >> from the idle loop. I'd suggest that you post the problematic code in > >> question to the list. > >> > > > > USB issue: > > > > Please refer to the USB patch attached (will be sent to the list as well > in a few minutes) > > As I mentioned previously, few drivers like GPIO, USB & UART have clock- > disable/enable + context save/restore in Idle path(omap_sram_idle()). > > > > In particular, I am referring to calling of the functions > pm_runtime_put_sync() & pm_runtime_get_sync() for USB around wfi. > > > > Now, the following call sequence from omap_sram_idle()will enable IRQs: > > pm_runtime_put_sync--> > > __pm_runtime_put--> > > pm_runtime_idle--> > > spin_unlock_irq(), > > __pm_runtime_idle(),--> > > spin_unlock_irq, > > spin_unlock_irq > > > > The functions pm_runtime_idle() & __ pm_runtime_idle() do not use > > spin_lock_irqsave & spin_unlock_irqrestore. This leads to enabling of > > the interrupts in omap_sram_idle unconditionally, which for USB in > > particular is leading to IO-pad interrupt being triggered which does > > not come otherwise. > > You seem to have correctly identified the problem. Can you try the > patch below (untested) which attempts to address the root cause you've > identified? > > Kevin > > > To work around this problem, instead of using Runtime APIs, we are using > omap_device_enable/disable, which in-turn call to __omap_hwmod_enable/idle > > > > Simply put, I am not talking about grabbing a mutex when interrupts are > disabled, rather of a scenario where interrupts are getting enabled as a > side-effect of calling these functions in omap_sram_idle(). > > From be3aeea5f8d29c8ce2fa278f48aef849eb682282 Mon Sep 17 00:00:00 2001 > From: Kevin Hilman <khil...@deeprootsystems.com> > Date: Mon, 9 Aug 2010 08:12:39 -0700 > Subject: [PATCH] PM: allow runtime PM get/put from interrupts-disabled > context > > When using runtime PM in combination with CPUidle, the runtime PM > transtions of some devices may be triggered during the idle path. > Late in the idle sequence, interrupts may already be disabled when > runtime PM for these devices is initiated (using the _sync versions of > the runtime PM API.) > > Currently, the runtime PM core assumes methods are called with > interrupts enabled. However, if it is called with interrupts > disabled, the internal locking unconditionally enables interrupts, for > example: > > pm_runtime_put_sync() > __pm_runtime_put() > pm_runtime_idle() > spin_lock_irq() > __pm_runtime_idle() > spin_unlock_irq() <--- interrupts unconditionally > enabled > dev->bus->pm->runtime_idle() > spin_lock_irq() > spin_unlock_irq() > > To fix, use the save/restore versions of the spinlock API. > Similar thing was thought when this problem was encountered but there was a concern that it may lead to interrupts are being disable for longer times
Are all run time PM APIs are short enough to keep interrupts disabled without impacting interrupt latency? -- 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
