Messages in this thread | | | Date | Sat, 28 Feb 2015 08:52:23 +0100 | From | Maxime Coquelin <> | Subject | Re: [STLinux Kernel] [PATCH 3/4] clk: Provide always-on clock support |
| |
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.
BR, Maxime
| |