From mboxrd@z Thu Jan 1 00:00:00 1970 From: khilman@linaro.org (Kevin Hilman) Date: Fri, 22 Nov 2013 10:43:49 -0800 Subject: [PATCH] PM / Clocks: fix pm_clk_resume/suspend if CONFIG_PM_RUNTIME is set In-Reply-To: <528D1C49.3020301@ti.com> (Santosh Shilimkar's message of "Wed, 20 Nov 2013 15:32:09 -0500") References: <1384954307-27094-1-git-send-email-grygorii.strashko@ti.com> <528D0296.1070001@codeaurora.org> <528D082C.3040405@ti.com> <528D1327.7080205@codeaurora.org> <528D1784.8080704@ti.com> <528D1C49.3020301@ti.com> Message-ID: <87ppps6zve.fsf@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Santosh Shilimkar writes: [...] >>> It looks like even if you just remove the locks here, the PM core is >>> free to call this function with irqs disabled if pm_runtime_irq_safe() >>> has been called on the device. Perhaps runtime PM can only do the >>> clk_enable()/clk_disable() part and the clk_unprepare()/clk_prepare() >>> calls should happen in the system suspend callbacks? >> >> Even don't know what to say :( On Keystone clk_unprepare()/clk_prepare() are NOPs. >> But clk_prepare() has to be called at least once before clk_enable() :(( >> So, solution with suspend/resume will not fix current problem :( unfortunately. >> >> FYI, Now pm_clk_suspend/pm_clk_resume are called from arch/arm/mach-keystone/pm_domain.c >> (also similar solution is used by Davinci, but issue has not been detected because >> PM runtime hasn't been used by Davinci IP drivers before) >> > One way to deal with this is to have clk_unprepare()/clk_prepare() > called from dev_pm_domain ops before calling pm_clk_[suspend/resume]() if we > can't have that as part of runtime code. That doesn't solve the irq_safe problem that Stephen pointed out without being very careful. Basically, if you have _any_ potentially sleeping calls in this path, you can never allow devices to use pm_runtime_irq_safe(). Also, I don't like having the clk_enable in the PM core but the clk_prepare in the platform-specific pm_domain. That seems prone for platforms to get wrong. I'll need to think about this a little more before having any idea what to do here. Kevin