Quoting Samuel Holland (2019-02-28 21:29:40) > The msgbox clock is critical because the hardware is shared between > Linux and system firmware. The message box may be used by the EL3 secure > monitor's PSCI implementation. On 64-bit sunxi SoCs, this is provided by > ARM TF-A; 32-bit SoCs use a different implementation. The secure monitor > uses the message box to forward requests to power management firmware > running on a separate CPU. > > It is not enough for the secure monitor to enable the clock each time > Linux performs a SMC into EL3, as both the firmware and Linux can run > concurrently on separate CPUs. So it is never safe for Linux to turn > this clock off, and it should be marked as critical. > > At this time, such power management firmware only exists for the A64. > However, it makes sense to take care of all CCU drivers now for > consistency, and to ease the transition in the future, once firmware is > ported to the other SoCs. > > Signed-off-by: Samuel Holland <sam...@sholland.org> > --- > drivers/clk/sunxi-ng/ccu-sun50i-a64.c | 2 +- > drivers/clk/sunxi-ng/ccu-sun50i-h6.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c > b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c > index 932836d26e2b..7780e855c56f 100644 > --- a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c > +++ b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c > @@ -350,7 +350,7 @@ static SUNXI_CCU_GATE(bus_de_clk, "bus-de", > "ahb1", > static SUNXI_CCU_GATE(bus_gpu_clk, "bus-gpu", "ahb1", > 0x064, BIT(20), 0); > static SUNXI_CCU_GATE(bus_msgbox_clk, "bus-msgbox", "ahb1", > - 0x064, BIT(21), 0); > + 0x064, BIT(21), CLK_IS_CRITICAL);
Please add a comment explaining why CLK_IS_CRITICAL is used. It helps us remember years from now without having to dig in the git history.
