linux-kernel - [PATCH v2 1/2] clk: meson: gxbb: Prepare the GPU clock tree to change at runtime

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Date:   Tue, 14 Apr 2020 21:50:30 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     jbrunet@...libre.com, linux-amlogic@...ts.infradead.org,
        linux-clk@...r.kernel.org
Cc:     narmstrong@...libre.com, mturquette@...libre.com, sboyd@...nel.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: gxbb: 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 propagate set_rate requests from the gate to the divider and from
the divider to the the mux so the GPU clock frequency can be updated at
runtime (which will be required for GPU DVFS). Don't propagate rate
changes to the mux parents because we don't want to change the MPLL
clocks (these are reserved for audio).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
---
 drivers/clk/meson/gxbb.c | 40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

diff --git a/drivers/clk/meson/gxbb.c b/drivers/clk/meson/gxbb.c
index 5fd6a574f8c3..0a68af6eec3d 100644
--- a/drivers/clk/meson/gxbb.c
+++ b/drivers/clk/meson/gxbb.c
@@ -957,7 +957,9 @@ static struct clk_regmap gxbb_sar_adc_clk = {
 
 /*
  * 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 gxbb_mali_0_1_parent_data[] = {
@@ -980,14 +982,15 @@ static struct clk_regmap gxbb_mali_0_sel = {
 	.hw.init = &(struct clk_init_data){
 		.name = "mali_0_sel",
 		.ops = &clk_regmap_mux_ops,
-		/*
-		 * bits 10:9 selects from 8 possible parents:
-		 * xtal, gp0_pll, mpll2, mpll1, fclk_div7,
-		 * fclk_div4, fclk_div3, fclk_div5
-		 */
 		.parent_data = gxbb_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,
 	},
 };
 
@@ -1004,7 +1007,7 @@ static struct clk_regmap gxbb_mali_0_div = {
 			&gxbb_mali_0_sel.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		.flags = CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -1020,7 +1023,7 @@ static struct clk_regmap gxbb_mali_0 = {
 			&gxbb_mali_0_div.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_GATE | CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -1033,14 +1036,15 @@ static struct clk_regmap gxbb_mali_1_sel = {
 	.hw.init = &(struct clk_init_data){
 		.name = "mali_1_sel",
 		.ops = &clk_regmap_mux_ops,
-		/*
-		 * bits 10:9 selects from 8 possible parents:
-		 * xtal, gp0_pll, mpll2, mpll1, fclk_div7,
-		 * fclk_div4, fclk_div3, fclk_div5
-		 */
 		.parent_data = gxbb_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,
 	},
 };
 
@@ -1057,7 +1061,7 @@ static struct clk_regmap gxbb_mali_1_div = {
 			&gxbb_mali_1_sel.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		.flags = CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -1073,7 +1077,7 @@ static struct clk_regmap gxbb_mali_1 = {
 			&gxbb_mali_1_div.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_GATE | CLK_SET_RATE_PARENT,
 	},
 };
 
@@ -1093,7 +1097,7 @@ static struct clk_regmap gxbb_mali = {
 		.ops = &clk_regmap_mux_ops,
 		.parent_hws = gxbb_mali_parent_hws,
 		.num_parents = 2,
-		.flags = CLK_SET_RATE_NO_REPARENT,
+		.flags = CLK_SET_RATE_PARENT,
 	},
 };
 
-- 
2.26.0