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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 08 Oct 2026, 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.

Imre, can you have a look at the issue, please?

BR,
Jani.

>
> 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.
>>
>>
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-- 
Jani Nikula, Intel