On Sat, 28 Feb 2015, Maxime Coquelin wrote: > Hi Lee, > > On 02/27/2015 10:14 PM, Lee Jones wrote: > >Lots of platforms contain clocks which if turned off would prove fatal. > >The only way to recover from these catastrophic failures is to restart > >the board(s). Now, when a clock is registered with the framework it is > >compared against a list of provided always-on clock names which must be > >kept ungated. If it matches, we enable the existing CLK_IGNORE_UNUSED > >flag, which will prevent the common clk framework from attempting to > >gate it during the clk_disable_unused() procedure. > > Please correct me if I'm wrong, but your patch does not fix the > issue you had initially. > Let's take an example: > A clock is critical for the system, and should never be gated, so > you add the CLK_IGNORE_UNUSED > flag so that it is not disabled by clk_disable_unused() procedure. > The same clock is also used by other IPs, for example spi 0 instance. > When starting a spi transfer, clk_enable() is called on this clock, > so its usecount becomes 1. > Once transfer done, clk_disable() is called, usecount becomes 0 and > the clock gets disabled: system freeze. You're right. I also need to extend clk_core_disable() to take notice of CLK_IGNORE_UNUSED. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
