Re: [PATCH 1/4] clk: rockchip: protect critical clocks from getting disabled

["Heiko Stübner" <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>]

Am Donnerstag, 31. Juli 2014, 17:30:25 schrieb Mike Turquette:
> Quoting Heiko Stübner (2014-07-31 16:29:34)
> 
> > Hi Mike,
> > 
> > Am Donnerstag, 31. Juli 2014, 15:45:23 schrieb Mike Turquette:
> > > Quoting Heiko Stuebner (2014-07-29 12:12:05)
> > > 
> > > > The clock-tree contains clocks that should never get disabled
> > > > automatically. One example are the base ACLKs, the base supplies for
> > > > all
> > > > peripherals.
> > > > 
> > > > Therefore add a structure similar to the sunxi clock-tree to protect
> > > > these
> > > > special clocks from being disabled.
> > > > 
> > > > Signed-off-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
> > > > ---
> > > > 
> > > >  drivers/clk/rockchip/clk-rk3188.c |  7 +++++++
> > > >  drivers/clk/rockchip/clk-rk3288.c |  7 +++++++
> > > >  drivers/clk/rockchip/clk.c        | 13 +++++++++++++
> > > >  drivers/clk/rockchip/clk.h        |  1 +
> > > >  4 files changed, 28 insertions(+)
> > > > 
> > > > diff --git a/drivers/clk/rockchip/clk-rk3188.c
> > > > b/drivers/clk/rockchip/clk-rk3188.c index a83a6d8..5aef277 100644
> > > > --- a/drivers/clk/rockchip/clk-rk3188.c
> > > > +++ b/drivers/clk/rockchip/clk-rk3188.c
> > > > @@ -599,6 +599,11 @@ static struct rockchip_clk_branch
> > > > rk3188_clk_branches[] __initdata = {>
> > > > 
> > > >         GATE(ACLK_GPS, "aclk_gps", "aclk_peri", 0,
> > > >         RK2928_CLKGATE_CON(8),
> > > >         13, GFLAGS),>
> > > >  
> > > >  };
> > > > 
> > > > +static const char *rk3188_critical_clocks[] __initconst = {
> > > > +       "aclk_cpu",
> > > > +       "aclk_peri",
> > > 
> > > I'm not against the idea of critical clocks, but I want to verify that
> > > there is no other driver out there that is a better fit for claiming
> > > these clks via clk_get and enabling them the normal way via clk_enable?
> > 
> > In the clock hierarchy of Rockchip SoCs, both aclks listed here, are
> > sources for pclk and hclk, as well as sourcing some other peripheral
> > gates further below too. So from what I've seen from the clock diagrams,
> > there is nothing that would claim these clocks directly, and it wouldn't
> > also make any sense to let them get disabled as there will always be
> > something using them (for example the dram-controller).
> 
> Sounds good. Just out of curiosity, under what circumstances would you
> want to gate them? Is there a use case for it?

hmm, I don't see a use-case for gating these at runtime right now, simply 
because there should be a user for them all the time. (both aclks combined 
have at least 68 consumers on the rk3288 and a similar number on the previous 
socs)

The only thing I could think of would be something suspend related - which we 
don't have yet. But then this would probably happen in the clock controller 
itself anyway in some late suspend-related action, so it could take into 
account them being defined as critical clocks.


Heiko
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