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Message-ID: <f19af3c6-f865-4758-8c50-aba40ec1cf68@amd.com>
Date: Fri, 6 Feb 2026 13:52:29 -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 16/19] drm/amd/display: Add parameter to control ALLM
behavior
On 2026-02-03 13:56, Tomasz Pakuła wrote:
> [Why]
> Some users prefer to always manually control ALLM/Gaming mode while
> others might want it permanently forced on.
>
> [How]
> Since there isn't yet an API to control this, expose module parameter
>
> Changes in v3:
> - Include a fix for possible NULL pointer dereference by Peter
>
> Closes: https://github.com/CachyOS/linux-cachyos/issues/680
>
> Co-developed-by: Peter Jung <admin@...1337.dev>
> Signed-off-by: Peter Jung <admin@...1337.dev>
> 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 | 14 +++++-
> .../gpu/drm/amd/display/dc/core/dc_resource.c | 7 +--
> .../amd/display/modules/inc/mod_info_packet.h | 1 +
> .../display/modules/info_packet/info_packet.c | 46 ++++++++++++++++---
> 5 files changed, 56 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 447e734c362b..312aa32064d5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -268,6 +268,7 @@ extern int amdgpu_rebar;
>
> extern int amdgpu_wbrf;
> extern int amdgpu_user_queue;
> +extern uint amdgpu_allm_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 d6d0a6e34c6b..4b038c8bbf9f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -248,6 +248,7 @@ int amdgpu_umsch_mm_fwlog;
> int amdgpu_rebar = -1; /* auto */
> int amdgpu_user_queue = -1;
> uint amdgpu_hdmi_hpd_debounce_delay_ms;
> +uint amdgpu_allm_mode = 1;
>
> DECLARE_DYNDBG_CLASSMAP(drm_debug_classes, DD_CLASS_TYPE_DISJOINT_BITS, 0,
> "DRM_UT_CORE",
> @@ -1124,7 +1125,7 @@ module_param_named(rebar, amdgpu_rebar, int, 0444);
> MODULE_PARM_DESC(user_queue, "Enable user queues (-1 = auto (default), 0 = disable, 1 = enable, 2 = enable UQs and disable KQs)");
> module_param_named(user_queue, amdgpu_user_queue, int, 0444);
>
> -/*
> +/**
> * DOC: hdmi_hpd_debounce_delay_ms (uint)
> * HDMI HPD disconnect debounce delay in milliseconds.
> *
> @@ -1134,6 +1135,17 @@ module_param_named(user_queue, amdgpu_user_queue, int, 0444);
> MODULE_PARM_DESC(hdmi_hpd_debounce_delay_ms, "HDMI HPD disconnect debounce delay in milliseconds (0 to disable (by default), 1500 is common)");
> module_param_named(hdmi_hpd_debounce_delay_ms, amdgpu_hdmi_hpd_debounce_delay_ms, uint, 0644);
>
> +/**
> + * DOC: allm_mode (int)
> + * Changes ALLM triggering mode (if sink supports ALLM). Possible values:
> + *
> + * - 0 = ALLM disabled
> + * - 1 = ALLM dynamically triggered based on VRR state / Game Content Type Hint
> + * - 2 = ALLM forced always on
> + */
> +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);
> +
> /* These devices are not supported by amdgpu.
> * They are supported by the mach64, r128, radeon drivers
> */
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> index 4a7c9f810e35..b779aac28dfa 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
> @@ -44,6 +44,7 @@
> #include "clk_mgr.h"
> #include "dc_state_priv.h"
> #include "dc_stream_priv.h"
> +#include "modules/inc/mod_info_packet.h"
Architecturally DC can't have a dependency on modules.
Is there a different way we can handle this?
Could we do the determination in amdgpu_dm (with help of
the module) and then set a flag on the stream?
Harry
>
> #include "virtual/virtual_link_hwss.h"
> #include "link/hwss/link_hwss_dio.h"
> @@ -4503,8 +4504,6 @@ static void set_avi_info_frame(
> unsigned int vic = pipe_ctx->stream->timing.vic;
> unsigned int rid = pipe_ctx->stream->timing.rid;
> unsigned int fr_ind = pipe_ctx->stream->timing.fr_index;
> - enum dc_timing_3d_format format;
> - bool allm;
>
> if (stream->avi_infopacket.valid) {
> *info_packet = stream->avi_infopacket;
> @@ -4658,10 +4657,8 @@ static void set_avi_info_frame(
> ///VIC
> if (pipe_ctx->stream->timing.hdmi_vic != 0)
> vic = 0;
> - format = stream->timing.timing_3d_format;
> - allm = stream->link->local_sink->edid_caps.allm;
> /*todo, add 3DStereo support*/
> - if ((format != TIMING_3D_FORMAT_NONE) || allm) {
> + if (!is_hdmi_vic_mode(pipe_ctx->stream)) {
> // Based on HDMI specs hdmi vic needs to be converted to cea vic when 3D is enabled
> switch (pipe_ctx->stream->timing.hdmi_vic) {
> case 1:
> diff --git a/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h b/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h
> index 306eb7355c25..9ec123ecc7c4 100644
> --- a/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h
> +++ b/drivers/gpu/drm/amd/display/modules/inc/mod_info_packet.h
> @@ -41,6 +41,7 @@ void set_vsc_packet_colorimetry_data(
> enum dc_color_space cs,
> enum color_transfer_func tf);
>
> +bool is_hdmi_vic_mode(const struct dc_stream_state *stream);
> void mod_build_vsc_infopacket(const struct dc_stream_state *stream,
> struct dc_info_packet *info_packet,
> enum dc_color_space cs,
> 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 53e488fdb4ea..829cce9455db 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
> @@ -23,12 +23,13 @@
> *
> */
>
> -#include "mod_info_packet.h"
> +#include "amdgpu.h"
> #include "core_types.h"
> -#include "dc_types.h"
> -#include "mod_shared.h"
> -#include "mod_freesync.h"
> #include "dc.h"
> +#include "dc_types.h"
> +#include "mod_freesync.h"
> +#include "mod_info_packet.h"
> +#include "mod_shared.h"
>
> enum vsc_packet_revision {
> vsc_packet_undefined = 0,
> @@ -54,6 +55,12 @@ enum vsc_packet_revision {
> #define HF_VSIF_3D_BIT 0
> #define HF_VSIF_ALLM_BIT 1
>
> +enum allm_trigger_mode {
> + ALLM_MODE_DISABLED = 0,
> + ALLM_MODE_ENABLED_DYNAMIC = 1,
> + ALLM_MODE_ENABLED_FORCED = 2,
> +};
> +
> // VTEM Byte Offset
> #define VTEM_PB0 0
> #define VTEM_PB1 1
> @@ -499,7 +506,32 @@ void mod_build_vsc_infopacket(const struct dc_stream_state *stream,
> }
> }
>
> -static bool is_hdmi_vic_mode(const struct dc_stream_state *stream)
> +static bool is_hdmi_allm_mode(const struct dc_stream_state *stream)
> +{
> + /* No local sink */
> + if (!stream->link->local_sink)
> + return false;
> +
> + /* Sink doesn't expose ALLM support in edid */
> + if (!stream->link->local_sink->edid_caps.allm)
> + return false;
> +
> + switch (amdgpu_allm_mode) {
> + case ALLM_MODE_DISABLED:
> + return false;
> +
> + case ALLM_MODE_ENABLED_DYNAMIC:
> + break;
> +
> + case ALLM_MODE_ENABLED_FORCED:
> + return true;
> + }
> +
> + return stream->content_type == DISPLAY_CONTENT_TYPE_GAME ||
> + stream->vrr_active_variable;
> +}
> +
> +bool is_hdmi_vic_mode(const struct dc_stream_state *stream)
> {
> if (stream->timing.hdmi_vic == 0)
> return false;
> @@ -512,7 +544,7 @@ static bool is_hdmi_vic_mode(const struct dc_stream_state *stream)
> if (stream->view_format != VIEW_3D_FORMAT_NONE)
> return false;
>
> - if (stream->link->local_sink->edid_caps.allm)
> + if (is_hdmi_allm_mode(stream))
> return false;
>
> return true;
> @@ -541,7 +573,7 @@ void mod_build_hf_vsif_infopacket(const struct dc_stream_state *stream,
>
> info_packet->valid = false;
>
> - allm = stream->link->local_sink->edid_caps.allm;
> + allm = is_hdmi_allm_mode(stream);
> format = stream->view_format == VIEW_3D_FORMAT_NONE ?
> TIMING_3D_FORMAT_NONE :
> stream->timing.timing_3d_format;
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