linux-kernel - Re: [PATCH v3 19/19] drm/amd/display: Add HDMI VRR desktop mode

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Message-ID: <ee4a21fc-3625-4086-b2d0-9acf20b5d2ef@amd.com>
Date: Fri, 6 Feb 2026 13:58:20 -0500
From: Harry Wentland <harry.wentland@....com>
To: Tomasz Pakuła <tomasz.pakula.oficjalny@...il.com>,
 alexander.deucher@....com, sunpeng.li@....com
Cc: maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
 tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
 siqueira@...lia.com, dri-devel@...ts.freedesktop.org,
 amd-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 bernhard.berger@...il.com, michel.daenzer@...lbox.org, daniel@...ishbar.org,
 admin@...1337.dev
Subject: Re: [PATCH v3 19/19] drm/amd/display: Add HDMI VRR desktop mode

On 2026-02-03 13:56, Tomasz Pakuła wrote:
> [Why]
> Many TVs and other HDMI sinks suffer from blanking and possibly other
> glitches when VRR is toggled. With FreeSync present on such sinks, they
> behave like the signal is always variable, even in fixed refresh rate
> situations.
> 
> [How]
> Keep HDMI VRR toggled if it's supported and not explicitly disabled.
> Additionnally, add module parameter which allows users to configure HDMI
> VRR triggering to only happen when the signal is truly asking for
> variable state. This is useful if end user has a TV that automatically
> toggles ALLM/Game mode when VRR is active and such user doesn't want
> gaming mode in normal desktop usage.
> 

Can't this already be done by the compositor by simply setting the
VRR_ENABLED property on a crtc?

I don't like doing behavior behind the backs of compositors that
they might not be expecting.

Harry

> Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@...il.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h                 |  1 +
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c             | 13 +++++++++++++
>  .../amd/display/modules/info_packet/info_packet.c   |  9 +++++++--
>  3 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 312aa32064d5..d49cd55e0f35 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -269,6 +269,7 @@ extern int amdgpu_rebar;
>  extern int amdgpu_wbrf;
>  extern int amdgpu_user_queue;
>  extern uint amdgpu_allm_mode;
> +extern bool amdgpu_hdmi_vrr_desktop_mode;
>  
>  extern uint amdgpu_hdmi_hpd_debounce_delay_ms;
>  
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 4b038c8bbf9f..f53c2ffeffa2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -249,6 +249,7 @@ int amdgpu_rebar = -1; /* auto */
>  int amdgpu_user_queue = -1;
>  uint amdgpu_hdmi_hpd_debounce_delay_ms;
>  uint amdgpu_allm_mode = 1;
> +bool amdgpu_hdmi_vrr_desktop_mode = true;
>  
>  DECLARE_DYNDBG_CLASSMAP(drm_debug_classes, DD_CLASS_TYPE_DISJOINT_BITS, 0,
>  			"DRM_UT_CORE",
> @@ -1146,6 +1147,18 @@ module_param_named(hdmi_hpd_debounce_delay_ms, amdgpu_hdmi_hpd_debounce_delay_ms
>  MODULE_PARM_DESC(allm_mode, "Changes ALLM trigger mode (0 = disable, 1 = enable (default), 2 = force enable)");
>  module_param_named(allm_mode, amdgpu_allm_mode, uint, 0644);
>  
> +/**
> + * DOC: hdmi_vrr_on_dekstop (bool)
> + * Enables FreeSync behavior mimicking by keeping HDMI VRR signalling active in
> + * fixed refresh rate conditions like normal desktop work/web browsing.
> + * Possible values:
> + *
> + * - false = HDMI VRR is only enabled if refresh rate is truly variable
> + * - true  = Mimics FreeSync behavior and keeps HDMI VRR always active
> + */
> +MODULE_PARM_DESC(hdmi_vrr_desktop_mode, "Changes HDMI VRR desktop mode (false = disable, true = enable (default))");
> +module_param_named(hdmi_vrr_desktop_mode, amdgpu_hdmi_vrr_desktop_mode, bool, 0644);
> +
>  /* These devices are not supported by amdgpu.
>   * They are supported by the mach64, r128, radeon drivers
>   */
> diff --git a/drivers/gpu/drm/amd/display/modules/info_packet/info_packet.c b/drivers/gpu/drm/amd/display/modules/info_packet/info_packet.c
> index 5fd9e8aadc98..b41e2240e1ae 100644
> --- a/drivers/gpu/drm/amd/display/modules/info_packet/info_packet.c
> +++ b/drivers/gpu/drm/amd/display/modules/info_packet/info_packet.c
> @@ -654,8 +654,13 @@ static void build_vtem_infopacket_data(const struct dc_stream_state *stream,
>  	bool vrr_active = false;
>  	bool rb = false;
>  
> -	vrr_active = vrr->state == VRR_STATE_ACTIVE_VARIABLE ||
> -		     vrr->state == VRR_STATE_ACTIVE_FIXED;
> +	if (amdgpu_hdmi_vrr_desktop_mode) {
> +		vrr_active = vrr->state != VRR_STATE_UNSUPPORTED &&
> +			     vrr->state != VRR_STATE_DISABLED;
> +	} else {
> +		vrr_active = vrr->state == VRR_STATE_ACTIVE_VARIABLE ||
> +			     vrr->state == VRR_STATE_ACTIVE_FIXED;
> +	}
>  
>  	infopacket->sb[VTEM_MD0] = VTEM_M_CONST << VTEM_M_CONST_BIT;
>  	infopacket->sb[VTEM_MD0] |= VTEM_FVA_FACTOR << VTEM_FVA_BIT;