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Subject[PATCH v2 1/2] clk: meson: meson8b: make the CCF use the glitch-free "mali" mux
Date
The "mali_0" or "mali_1" clock trees should not be updated while the
clock is running. Enforce this by setting CLK_SET_RATE_GATE on the
"mali_0" and "mali_1" gates. This makes the CCF switch to the "mali_1"
tree when "mali_0" is currently active and vice versa, which is exactly
what the vendor driver does when updating the frequency of the mali
clock.

This fixes a potential hang when changing the GPU frequency at runtime.

Fixes: 74e1f2521f16ff ("clk: meson: meson8b: add the GPU clock tree")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
---
drivers/clk/meson/meson8b.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
index 3408297bff65..9fd31f23b2a9 100644
--- a/drivers/clk/meson/meson8b.c
+++ b/drivers/clk/meson/meson8b.c
@@ -1772,8 +1772,11 @@ static struct clk_regmap meson8b_hdmi_sys = {

/*
* The MALI IP is clocked by two identical clocks (mali_0 and mali_1)
- * muxed by a glitch-free switch on Meson8b and Meson8m2. Meson8 only
- * has mali_0 and no glitch-free mux.
+ * muxed by a glitch-free switch on Meson8b and Meson8m2. The CCF can
+ * actually manage this glitch-free mux because it does top-to-bottom
+ * updates the each clock tree and switches to the "inactive" one when
+ * CLK_SET_RATE_GATE is set.
+ * Meson8 only has mali_0 and no glitch-free mux.
*/
static const struct clk_parent_data meson8b_mali_0_1_parent_data[] = {
{ .fw_name = "xtal", .name = "xtal", .index = -1, },
@@ -1838,7 +1841,7 @@ static struct clk_regmap meson8b_mali_0 = {
&meson8b_mali_0_div.hw
},
.num_parents = 1,
- .flags = CLK_SET_RATE_PARENT,
+ .flags = CLK_SET_RATE_GATE | CLK_SET_RATE_PARENT,
},
};

@@ -1893,7 +1896,7 @@ static struct clk_regmap meson8b_mali_1 = {
&meson8b_mali_1_div.hw
},
.num_parents = 1,
- .flags = CLK_SET_RATE_PARENT,
+ .flags = CLK_SET_RATE_GATE | CLK_SET_RATE_PARENT,
},
};

--
2.24.1
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