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

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Message-ID: <d0ec285d-6a27-4f28-b622-6048a9dcb6e8@linaro.org>
Date: Fri, 14 Feb 2025 12:15:14 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Martijn van Deventer <linux@...tijnvandeventer.nl>,
 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: Re: [PATCH] clk: meson: g12a: Fix kernel warnings when no display
 attached

On 13/02/2025 23:17, Martijn van Deventer wrote:
> 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,
>   	},
>   };
>   

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>