linux-kernel - [PATCH v2 1/2] clk: meson: meson8b: make the CCF use the glitch-free "mali" mux

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Message-Id: <20191226191224.3785282-2-martin.blumenstingl@googlemail.com>
Date:   Thu, 26 Dec 2019 20:12:23 +0100
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     linux-amlogic@...ts.infradead.org, jbrunet@...libre.com,
        sboyd@...nel.org
Cc:     narmstrong@...libre.com, mturquette@...libre.com,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH v2 1/2] clk: meson: meson8b: make the CCF use the glitch-free "mali" mux

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@...glemail.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