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From: Martin Blumenstingl <>
	Martin Blumenstingl <>
Subject: [RFC v1 5/7] clk: meson: meson8b: mark the CPU clock as CLK_IS_CRITICAL
Date: Wed, 14 Nov 2018 23:57:23 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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 <>
 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 |

  parent reply	other threads:[~2018-11-14 22:58 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-14 22:57 [RFC v1 0/7] Meson8b: make the CPU clock mutable Martin Blumenstingl
2018-11-14 22:57 ` [RFC v1 1/7] clk: meson: meson8b: run from the XTAL when changing the CPU frequency Martin Blumenstingl
2018-11-15  9:53   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 2/7] clk: meson: meson8b: do not use cpu_div3 for cpu_scale_out_sel Martin Blumenstingl
2018-11-15  9:42   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 3/7] clk: meson: clk-pll: check if the clock is already enabled Martin Blumenstingl
2018-11-15  9:14   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 4/7] clk: meson: clk-pll: add the is_enabled function in the clk_ops Martin Blumenstingl
2018-11-15  9:16   ` Jerome Brunet
2018-11-14 22:57 ` Martin Blumenstingl [this message]
2018-11-15  9:46   ` [RFC v1 5/7] clk: meson: meson8b: mark the CPU clock as CLK_IS_CRITICAL Jerome Brunet
2018-11-14 22:57 ` [RFC v1 6/7] clk: meson: meson8b: add support for more M/N values in sys_pll Martin Blumenstingl
2018-11-15  9:41   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 7/7] clk: meson: meson8b: allow changing the CPU clock tree Martin Blumenstingl
2018-11-15  9:46   ` Jerome Brunet
2018-11-15 10:08 ` [RFC v1 0/7] Meson8b: make the CPU clock mutable Neil Armstrong

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