On Tue, 2 Nov 2021 at 03:16, ChiaWei Wang <chiawei_w...@aspeedtech.com> wrote: > > Hi Jae, > > > From: linux-arm-kernel <linux-arm-kernel-boun...@lists.infradead.org> On > > > > From: Jae Hyun Yoo <jae.hyun....@linux.intel.com> > > > > If LPC KCS driver is registered ahead of lpc-ctrl module, LPC KCS block > > will be > > enabled without heart beating of LCLK until lpc-ctrl enables the LCLK. This > > issue causes improper handling on host interrupts when the host sends > > interrupts in that time frame. > > Then kernel eventually forcibly disables the interrupt with dumping stack > > and > > printing a 'nobody cared this irq' message out. > > > > To prevent this issue, all LPC sub drivers should enable LCLK individually > > so this > > patch adds clock control logic into the LPC KCS driver. > > Have all LPC sub drivers could result in entire LPC block down if any of them > disables the clock (e.g. driver unload). > The LPC devices such as SIO can be used before kernel booting, even without > any BMC firmware. > Thereby, we recommend to make LCLK critical or guarded by protected clock > instead of having all LPC sub drivers hold the LCLK control. > > The previous discussion for your reference: > https://lkml.org/lkml/2020/9/28/153
Please read the entire thread. The conclusion: https://lore.kernel.org/all/cacpk8xdbmkhz8mcsfmdafv8k7qj7ajbl8tvkfk8c+5aneum...@mail.gmail.com/ That is, for the devices that have a driver loaded can enable the clock. When they are unloaded, they will reduce the reference count until the last driver is unloaded. eg: https://elixir.bootlin.com/linux/latest/source/drivers/clk/clk.c#L945 There was another fork to the thread, where we suggested that a protected clocks binding could be added: https://lore.kernel.org/all/160269577311.884498.8429245140509326...@swboyd.mtv.corp.google.com/ If you wish to use this mechanism for eg. SIO clocks, then I encourage Aspeed to submit a patch to do that. Cheers, Joel _______________________________________________ Openipmi-developer mailing list Openipmi-developer@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openipmi-developer
