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>]

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.

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.