drm/i915/aux: use polling when irqs are unavailable

PTL with physically disconnected display was observed to have 40s longer
execution time when testing xe_fault_injection@xe_guc_mmio_send_recv.
The issue has not been seen when reverting commit 40a9f77a28fa ("Revert
"drm/i915/dp: change aux_ctl reg read to polling read"").

Apparently the configuration suffers from not having AUX enabled when
using interrupts. One probable cause can be xe enabling interrupts too
late: interrupts need memory allocations which currently can't be done
before the display FB takeover is done.

As for now, use polling for AUX in case interrupts are unavailable.

Fixes: 40a9f77a28fa ("Revert "drm/i915/dp: change aux_ctl reg read to polling read"")
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Michał Grzelak <michal.grzelak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260416163744.288107-1-michal.grzelak@intel.com
(cherry picked from commit 05e0550b65cd1604bd515fbc65f522bce4c10a87)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index b20ec3e589fadc4972efb77286978f38a527bd1c..9c9b6410366d5ca3558a3aad1e8dc34dde47e9c0 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -12,6 +12,7 @@
 #include "intel_dp.h"
 #include "intel_dp_aux.h"
 #include "intel_dp_aux_regs.h"
+#include "intel_parent.h"
 #include "intel_pps.h"
 #include "intel_quirks.h"
 #include "intel_tc.h"
@@ -60,18 +61,29 @@ intel_dp_aux_wait_done(struct intel_dp *intel_dp)
        struct intel_display *display = to_intel_display(intel_dp);
        i915_reg_t ch_ctl = intel_dp->aux_ch_ctl_reg(intel_dp);
        const unsigned int timeout_ms = 10;
+       bool done = true;
        u32 status;
-       bool done;
+       int ret;
 
+       if (intel_parent_irq_enabled(display)) {
 #define C (((status = intel_de_read_notrace(display, ch_ctl)) & DP_AUX_CH_CTL_SEND_BUSY) == 0)
-       done = wait_event_timeout(display->gmbus.wait_queue, C,
-                                 msecs_to_jiffies_timeout(timeout_ms));
+               done = wait_event_timeout(display->gmbus.wait_queue, C,
+                                         msecs_to_jiffies_timeout(timeout_ms));
+
+#undef C
+       } else {
+               ret = intel_de_wait_ms(display, ch_ctl,
+                                      DP_AUX_CH_CTL_SEND_BUSY, 0,
+                                      timeout_ms, &status);
+
+               if (ret == -ETIMEDOUT)
+                       done = false;
+       }
 
        if (!done)
                drm_err(display->drm,
                        "%s: did not complete or timeout within %ums (status 0x%08x)\n",
                        intel_dp->aux.name, timeout_ms, status);
-#undef C
 
        return status;
 }