Re: adlp_tc_phy_connect [i915] floods logs with drm_WARN_ON(tc->mode == TC_PORT_LEGACY) call traces

["jp_2422-git@yahoo.com" <jp_2422-git@yahoo.com>]

Ok, thanks. I 'll keep it just as a private fix in the absence a suitable bios update.


On Thursday, 8 October 2026 at 12:49:19 BST, Jani Nikula <jani.nikula@linux.intel.com> wrote: 





On Thu, 08 Oct 2026, "jp_2422-git@yahoo.com" <jp_2422-git@yahoo.com> wrote:
> The issue discussed at https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/12246 affects a number of laptops and Bios combinations, and appears to be the result of buggy Bios'es where the Intel VBT table is listing non-existent Display Ports on Alder Lake laptops.
>
> The following patch skips the creation of the non-existent port early
> on in intel_ddi_init(), so preventing the logs from being flooded with
> the warnings. It uses a new i915 display parameter to allow the user
> to select the type c port to skip with a boot option, and fixes the
> problem. Please can you advise whether you would accept this patch.

Thanks for the patch, but sorry, module parameters aren't the solution
to work around issues.

BR,
Jani.

>
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index a46ab5d3d..5b9ebdecd 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -50,6 +50,7 @@
> #include "intel_ddi_buf_trans.h"
> #include "intel_de.h"
> #include "intel_dip.h"
> +#include "intel_display_params.h"
> #include "intel_display_power.h"
> #include "intel_display_regs.h"
> #include "intel_display_types.h"
> @@ -5239,6 +5240,24 @@ static const char *intel_ddi_encoder_name(struct intel_display *display,
> return seq_buf_str(s);
> }
>
> +static enum port get_skip_tc_port_param(struct intel_display *display)
> +{
> + const char *param;
> + enum port port;
> +
> + param=display->params.skip_tc_port;
> +
> + if(param==NULL)
> + return PORT_NONE;
> +
> + for_each_port(port) {
> + if (port_name(port)==*param)
> + return port;
> + }
> +
> + return PORT_NONE;
> +}
> +
> void intel_ddi_init(struct intel_display *display,
> const struct intel_bios_encoder_data *devdata)
> {
> @@ -5249,11 +5268,20 @@ void intel_ddi_init(struct intel_display *display,
> enum port port;
> enum phy phy;
> u32 ddi_buf_ctl;
> + enum port skip_tc_port_param;
>
> port = intel_bios_encoder_port(devdata);
> if (port == PORT_NONE)
> return;
>
> + skip_tc_port_param=get_skip_tc_port_param(display);
> +
> + if(port == skip_tc_port_param) {
> + drm_dbg_kms(display->drm,
> + "Skipping creation of Port %c due to the skip_tc_port parameter\n", port_name(port));
> + return;
> + }
> +
> if (!port_strap_detected(display, port)) {
> drm_dbg_kms(display->drm,
> "Port %c strap not detected\n", port_name(port));
> diff --git a/drivers/gpu/drm/i915/display/intel_display_params.c b/drivers/gpu/drm/i915/display/intel_display_params.c
> index ca0ef466b..2f516ca4e 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_params.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_params.c
> @@ -143,6 +143,10 @@ intel_display_param_named_unsafe(enable_dmc_wl, int, 0400,
> "(-1=use per-chip default, 0=disabled, 1=enabled, 2=match any register, 3=always locked) "
> "Default: -1");
>
> +intel_display_param_named_unsafe(skip_tc_port, charp, 0400,
> + "Skip the use of the specified Type-C port "
> + " (single letter in the range [A - I])");
> +
> __maybe_unused
> static void _param_print_bool(struct drm_printer *p, const char *driver_name,
> const char *name, bool val)
> diff --git a/drivers/gpu/drm/i915/display/intel_display_params.h b/drivers/gpu/drm/i915/display/intel_display_params.h
> index 5c5a1a135..6356438f6 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_params.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_params.h
> @@ -51,6 +51,7 @@ struct drm_printer;
> param(bool, psr_safest_params, false, 0400) \
> param(bool, enable_psr2_sel_fetch, true, 0400) \
> param(int, enable_dmc_wl, -1, 0400) \
> + param(char *, skip_tc_port, NULL, 0400) \
> /*
> * Debugfs-only knob (per-device): no matching module_param is registered
> * in intel_display_params.c on purpose. Runtime-toggle via debugfs.
>
>
>
>
>
>
>
>
>
>

-- 
Jani Nikula, Intel