linux-kernel - [RFC v1 2/5] clk: meson: g12a: Prepare the GPU clock tree to change at runtime

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Date:   Tue, 31 Mar 2020 00:11:01 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     linux-amlogic@...ts.infradead.org, khilman@...libre.com,
        jbrunet@...libre.com, narmstrong@...libre.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [RFC v1 2/5] clk: meson: g12a: Prepare the GPU clock tree to change at runtime

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.
Also populate set_rate requests from the divider to the mux so the GPU
clock frequency can be updated at runtime (which will be required for
GPU DVFS).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
---
 drivers/clk/meson/g12a.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/meson/g12a.c b/drivers/clk/meson/g12a.c
index fad616cac01e..30c15766ebb1 100644
--- a/drivers/clk/meson/g12a.c
+++ b/drivers/clk/meson/g12a.c
@@ -3702,7 +3702,9 @@ static struct clk_regmap g12a_hdmi = {
 
 /*
  * The MALI IP is clocked by two identical clocks (mali_0 and mali_1)
- * muxed by a glitch-free switch.
+ * muxed by a glitch-free switch. The CCF can 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.
  */
 static const struct clk_parent_data g12a_mali_0_1_parent_data[] = {
 	{ .fw_name = "xtal", },
@@ -3726,7 +3728,13 @@ static struct clk_regmap g12a_mali_0_sel = {
 		.ops = &clk_regmap_mux_ops,
 		.parent_data = g12a_mali_0_1_parent_data,
 		.num_parents = 8,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		/*
+		 * Don't request the parent to change the rate because
+		 * all GPU frequencies can be derived from the fclk_*
+		 * clocks and one special GP0_PLL setting. This is
+		 * important because we need the MPLL clocks for audio.
+		 */
+		.flags = 0,
 	},
 };
 
@@ -3743,7 +3751,7 @@ static struct clk_regmap g12a_mali_0_div = {
 			&g12a_mali_0_sel.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		.flags = CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -3759,7 +3767,7 @@ static struct clk_regmap g12a_mali_0 = {
 			&g12a_mali_0_div.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_GATE | CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -3774,7 +3782,13 @@ static struct clk_regmap g12a_mali_1_sel = {
 		.ops = &clk_regmap_mux_ops,
 		.parent_data = g12a_mali_0_1_parent_data,
 		.num_parents = 8,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		/*
+		 * Don't request the parent to change the rate because
+		 * all GPU frequencies can be derived from the fclk_*
+		 * clocks and one special GP0_PLL setting. This is
+		 * important because we need the MPLL clocks for audio.
+		 */
+		.flags = 0,
 	},
 };
 
@@ -3791,7 +3805,7 @@ static struct clk_regmap g12a_mali_1_div = {
 			&g12a_mali_1_sel.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		.flags = CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -3807,7 +3821,7 @@ static struct clk_regmap g12a_mali_1 = {
 			&g12a_mali_1_div.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_GATE | CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -3827,7 +3841,7 @@ static struct clk_regmap g12a_mali = {
 		.ops = &clk_regmap_mux_ops,
 		.parent_hws = g12a_mali_parent_hws,
 		.num_parents = 2,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		.flags = CLK_SET_RATE_PARENT,
 	},
 };
 
-- 
2.26.0