| Message ID | 20181114225725.2821-6-martin.blumenstingl@googlemail.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | Meson8b: make the CPU clock mutable | expand |
On Wed, 2018-11-14 at 23:57 +0100, Martin Blumenstingl wrote: > We don't want the common clock framework to disable the "cpu_clk" if > it's not used by any device. The cpufreq-dt driver does not enable the > CPU clocks. However, even if it would we would still want the CPU clock > to be enabled at all times because the CPU clock is also required even > if we disable CPU frequency scaling on a specific board. > > The reason why we want the CPU clock to be enabled is a clock further up > in the tree: > Since commit 6f888e7bc7bd58 ("clk: meson: clk-pll: add enable bit") the > sys_pll can be disabled. However, since the CPU clock is derived from > sys_pll we don't want sys_pll to get disabled. The common clock > framework takes care of that for us by enabling all parent clocks of our > CPU clock when we mark the CPU clock with CLK_IS_CRITICAL. > > Until now this is not a problem yet because all clocks in the CPU > clock's tree (including sys_pll) are read-only. However, once we allow > modifications to the clocks in that tree we will need this. > > Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> > --- > drivers/clk/meson/meson8b.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c > index 8a3c346e110d..d566dd5bc567 100644 > --- a/drivers/clk/meson/meson8b.c > +++ b/drivers/clk/meson/meson8b.c > @@ -646,7 +646,8 @@ static struct clk_regmap meson8b_cpu_clk = { > "cpu_scale_out_sel" }, > .num_parents = 2, > .flags = (CLK_SET_RATE_PARENT | > - CLK_SET_RATE_NO_REPARENT), > + CLK_SET_RATE_NO_REPARENT | > + CLK_IS_CRITICAL), > }, > }; > Acked-by: Jerome Brunet <jbrunet@baylibre.com>
diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c index 8a3c346e110d..d566dd5bc567 100644 --- a/drivers/clk/meson/meson8b.c +++ b/drivers/clk/meson/meson8b.c @@ -646,7 +646,8 @@ static struct clk_regmap meson8b_cpu_clk = { "cpu_scale_out_sel" }, .num_parents = 2, .flags = (CLK_SET_RATE_PARENT | - CLK_SET_RATE_NO_REPARENT), + CLK_SET_RATE_NO_REPARENT | + CLK_IS_CRITICAL), }, };
We don't want the common clock framework to disable the "cpu_clk" if it's not used by any device. The cpufreq-dt driver does not enable the CPU clocks. However, even if it would we would still want the CPU clock to be enabled at all times because the CPU clock is also required even if we disable CPU frequency scaling on a specific board. The reason why we want the CPU clock to be enabled is a clock further up in the tree: Since commit 6f888e7bc7bd58 ("clk: meson: clk-pll: add enable bit") the sys_pll can be disabled. However, since the CPU clock is derived from sys_pll we don't want sys_pll to get disabled. The common clock framework takes care of that for us by enabling all parent clocks of our CPU clock when we mark the CPU clock with CLK_IS_CRITICAL. Until now this is not a problem yet because all clocks in the CPU clock's tree (including sys_pll) are read-only. However, once we allow modifications to the clocks in that tree we will need this. Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> --- drivers/clk/meson/meson8b.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)