The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x c87514a0bb0a64507412a2d98264060dc0c1562a # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025082320-stooge-trekker-dc42@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From c87514a0bb0a64507412a2d98264060dc0c1562a Mon Sep 17 00:00:00 2001 From: Imre Deak imre.deak@intel.com Date: Mon, 11 Aug 2025 11:01:50 +0300 Subject: [PATCH] drm/i915/lnl+/tc: Fix max lane count HW readout
On LNL+ for a disconnected sink the pin assignment value gets cleared by the HW/FW as soon as the sink gets disconnected, even if the PHY ownership got acquired already by the BIOS/driver (and hence the PHY itself is still connected and used by the display). During HW readout this can result in detecting the PHY's max lane count as 0 - matching the above cleared aka NONE pin assignment HW state. For a connected PHY the driver in general (outside of intel_tc.c) expects the max lane count value to be valid for the video mode enabled on the corresponding output (1, 2 or 4). Ensure this by setting the max lane count to 4 in this case. Note, that it doesn't matter if this lane count happened to be more than the max lane count with which the PHY got connected and enabled, since the only thing the driver can do with such an output - where the DP-alt sink is disconnected - is to disable the output.
v2: Rebased on change reading out the pin configuration only if the PHY is connected.
Cc: stable@vger.kernel.org # v6.8+ Reported-by: Charlton Lin charlton.lin@intel.com Tested-by: Khaled Almahallawy khaled.almahallawy@intel.com Reviewed-by: Mika Kahola mika.kahola@intel.com Signed-off-by: Imre Deak imre.deak@intel.com Link: https://lore.kernel.org/r/20250811080152.906216-4-imre.deak@intel.com (cherry picked from commit 33cf70bc0fe760224f892bc1854a33665f27d482) Signed-off-by: Tvrtko Ursulin tursulin@ursulin.net
diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c index 34435c4fc280..3f9842040bb0 100644 --- a/drivers/gpu/drm/i915/display/intel_tc.c +++ b/drivers/gpu/drm/i915/display/intel_tc.c @@ -23,6 +23,7 @@ #include "intel_modeset_lock.h" #include "intel_tc.h"
+#define DP_PIN_ASSIGNMENT_NONE 0x0 #define DP_PIN_ASSIGNMENT_C 0x3 #define DP_PIN_ASSIGNMENT_D 0x4 #define DP_PIN_ASSIGNMENT_E 0x5 @@ -308,6 +309,8 @@ static int lnl_tc_port_get_max_lane_count(struct intel_digital_port *dig_port) REG_FIELD_GET(TCSS_DDI_STATUS_PIN_ASSIGNMENT_MASK, val);
switch (pin_assignment) { + case DP_PIN_ASSIGNMENT_NONE: + return 0; default: MISSING_CASE(pin_assignment); fallthrough; @@ -1159,6 +1162,12 @@ static void xelpdp_tc_phy_get_hw_state(struct intel_tc_port *tc) tc->lock_wakeref = tc_cold_block(tc);
read_pin_configuration(tc); + /* + * Set a valid lane count value for a DP-alt sink which got + * disconnected. The driver can only disable the output on this PHY. + */ + if (tc->max_lane_count == 0) + tc->max_lane_count = 4; }
drm_WARN_ON(display->drm,