linux-kernel - [PATCH] clk: meson: g12a: Fix kernel warnings when no display attached

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Message-Id: <20250213221702.606-1-linux@martijnvandeventer.nl>
Date: Thu, 13 Feb 2025 23:17:01 +0100
From: Martijn van Deventer <linux@...tijnvandeventer.nl>
To: Neil Armstrong <neil.armstrong@...aro.org>,
	Jerome Brunet <jbrunet@...libre.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Kevin Hilman <khilman@...libre.com>,
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc: linux-amlogic@...ts.infradead.org,
	linux-clk@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] clk: meson: g12a: Fix kernel warnings when no display attached

When booting SM1 or G12A boards without a dislay attached to HDMI,
the kernel shows the following warning:

[CRTC:46:meson_crtc] vblank wait timed out
WARNING: CPU: 2 PID: 265 at drivers/gpu/drm/drm_atomic_helper.c:1682 drm_atomic_helper_wait_for_vblanks.part.0+0x240/0x264
CPU: 2 UID: 0 PID: 265 Comm: setfont Tainted: G         C
Tainted: [C]=CRAP
pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : drm_atomic_helper_wait_for_vblanks.part.0+0x240/0x264
lr : drm_atomic_helper_wait_for_vblanks.part.0+0x240/0x264
Call trace:
 drm_atomic_helper_wait_for_vblanks.part.0+0x240/0x264
 drm_atomic_helper_commit_tail_rpm+0x84/0xa0
 commit_tail+0xa4/0x18c
 drm_atomic_helper_commit+0x164/0x178
 drm_atomic_commit+0xb4/0xec
 drm_client_modeset_commit_atomic+0x210/0x270
 drm_client_modeset_commit_locked+0x5c/0x188
 drm_fb_helper_pan_display+0xb8/0x1d4
 fb_pan_display+0x7c/0x120
 bit_update_start+0x20/0x48
 fbcon_switch+0x418/0x54c
 el0t_64_sync+0x194/0x198

This happens when the kernel disables the unused clocks.
Sometimes this causes the boot to hang.

By (re)adding the flag CLK_IGNORE_UNUSED to the VCLK2 clocks, these
clocks will not be disabled.

This partially reverts commit b70cb1a21a54 ("clk: meson: g12a:
make VCLK2 and ENCL clock path configurable by CCF").

Fixes: b70cb1a21a54 ("clk: meson: g12a: make VCLK2 and ENCL clock path configurable by CCF").
Signed-off-by: Martijn van Deventer <linux@...tijnvandeventer.nl>
---
 drivers/clk/meson/g12a.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/meson/g12a.c b/drivers/clk/meson/g12a.c
index cfffd434e998..1651898658f5 100644
--- a/drivers/clk/meson/g12a.c
+++ b/drivers/clk/meson/g12a.c
@@ -3234,7 +3234,7 @@ static struct clk_regmap g12a_vclk2_div = {
 			&g12a_vclk2_input.hw
 		},
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_GATE,
+		.flags = CLK_SET_RATE_GATE | CLK_IGNORE_UNUSED,
 	},
 };
 
@@ -3270,7 +3270,7 @@ static struct clk_regmap g12a_vclk2 = {
 		.ops = &meson_vclk_gate_ops,
 		.parent_hws = (const struct clk_hw *[]) { &g12a_vclk2_div.hw },
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED,
 	},
 };
 
@@ -3354,7 +3354,7 @@ static struct clk_regmap g12a_vclk2_div1 = {
 		.ops = &clk_regmap_gate_ops,
 		.parent_hws = (const struct clk_hw *[]) { &g12a_vclk2.hw },
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED,
 	},
 };
 
@@ -3368,7 +3368,7 @@ static struct clk_regmap g12a_vclk2_div2_en = {
 		.ops = &clk_regmap_gate_ops,
 		.parent_hws = (const struct clk_hw *[]) { &g12a_vclk2.hw },
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED,
 	},
 };
 
@@ -3382,7 +3382,7 @@ static struct clk_regmap g12a_vclk2_div4_en = {
 		.ops = &clk_regmap_gate_ops,
 		.parent_hws = (const struct clk_hw *[]) { &g12a_vclk2.hw },
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED,
 	},
 };
 
@@ -3396,7 +3396,7 @@ static struct clk_regmap g12a_vclk2_div6_en = {
 		.ops = &clk_regmap_gate_ops,
 		.parent_hws = (const struct clk_hw *[]) { &g12a_vclk2.hw },
 		.num_parents = 1,
-		.flags = CLK_SET_RATE_PARENT,
+		.flags = CLK_SET_RATE_PARENT | CLK_IGNORE_UNUSED,
 	},
 };
 
-- 
2.39.2