linux-kernel - Re: [PATCH v2 2/4] clk: rockchip: rk3228: make noc and some special clk as critical

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Date:   Thu, 30 Mar 2017 15:19:28 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     Elaine Zhang <zhangqing@...k-chips.com>, xf@...k-chips.com,
        huangtao@...k-chips.com, mturquette@...libre.com,
        sboyd@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        xxx@...k-chips.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/4] clk: rockchip: rk3228: make noc and some special
 clk as critical_clocks

On Thu, Mar 30, 2017 at 03:10:24PM +0200, Heiko Stuebner wrote:
> Am Donnerstag, 30. März 2017, 14:44:17 CEST schrieb Maxime Ripard:
> > On Tue, Mar 28, 2017 at 06:06:52PM +0800, Elaine Zhang wrote:
> > > Signed-off-by: Elaine Zhang <zhangqing@...k-chips.com>
> > > ---
> > >  drivers/clk/rockchip/clk-rk3228.c | 30 +++++++++++++++++++++++++++++-
> > >  1 file changed, 29 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/clk/rockchip/clk-rk3228.c b/drivers/clk/rockchip/clk-rk3228.c
> > > index db6e5a9e6de6..4d3203f887e2 100644
> > > --- a/drivers/clk/rockchip/clk-rk3228.c
> > > +++ b/drivers/clk/rockchip/clk-rk3228.c
> > > @@ -445,7 +445,7 @@ enum rk3228_plls {
> > >  			RK2928_CLKGATE_CON(2), 12, GFLAGS,
> > >  			&rk3228_spdif_fracmux),
> > >  
> > > -	GATE(0, "jtag", "ext_jtag", 0,
> > > +	GATE(0, "jtag", "ext_jtag", CLK_IGNORE_UNUSED,
> > 
> > CLK_IGNORE_UNUSED only prevents a given clock from being gated at
> > late_initcall time, but will not prevent it from being gated later in
> > the life of the system, for example if a reparenting occurs, or if all
> > the clocks sharing the same clock tree become disabled.
> > 
> > If your clock really should never ever be gated in order for Linux to
> > operate properly, you should use CLK_IS_CRITICAL.
> 
> in the scope of the jtag clock, that is actually ok. As it only gates
> some clock supplied from an external source (ext_jtag).

It might, I don't know how your clocks work in general, this was just
a warning that this probably isn't sufficient if the clock is actually
critical.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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