[PATCH v7 14/26] drm/i915/display: Make set_pipeconf use the fw variants

Maarten Lankhorst
2026-03-10T11:57:46Z

The calls are used inside the critical section when updating
the gamma mode, and thus should use the _fw variants to prevent
locks.

Fixes following splat:
| BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
| in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 2115, name: modprobe
| preempt_count: 0, expected: 0
| RCU nest depth: 0, expected: 0
| 4 locks held by modprobe/2115:
| #0: ffff99b9425161a0 (&dev->mutex){....}-{4:4}, at: __driver_attach+0xaf/0x1c0
| #1: ffffaa224810f6c0 (crtc_ww_class_acquire){+.+.}-{0:0}, at: intel_initial_commit+0x4c/0x200 [i915]
| #2: ffffaa224810f6e8 (crtc_ww_class_mutex){+.+.}-{4:4}, at: intel_initial_commit+0x4c/0x200 [i915]
| #3: ffff99b94a6c9030 (&uncore->lock){+.+.}-{3:3}, at: gen6_write32+0x50/0x290 [i915]
| irq event stamp: 513344
| hardirqs last enabled at (513343): [<ffffffff8ba8d84c>] _raw_spin_unlock_irqrestore+0x4c/0x60
| hardirqs last disabled at (513344): [<ffffffffc1543646>] intel_pipe_update_start+0x216/0x2c0 [i915]
| softirqs last enabled at (512766): [<ffffffff8af045cf>] __local_bh_enable_ip+0x10f/0x170
| softirqs last disabled at (512712): [<ffffffffc14dfb6a>] __i915_request_queue+0x3a/0x70 [i915]
| CPU: 3 UID: 0 PID: 2115 Comm: modprobe Tainted: G W 6.18.0-rc1+ #17 PREEMPT_{RT,(lazy)}
| Tainted: [W]=WARN
| Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./Z68 Pro3-M, BIOS P2.30 06/29/2012
| Call Trace:
| <TASK>
| dump_stack_lvl+0x68/0x90
| __might_resched.cold+0xf0/0x12b
| rt_spin_lock+0x5f/0x200
| gen6_write32+0x50/0x290 [i915]
| ilk_set_pipeconf+0x12d/0x230 [i915]
| ilk_color_commit_arm+0x2d/0x70 [i915]
| intel_update_crtc+0x15b/0x690 [i915]
| intel_commit_modeset_enables+0xa6/0xd0 [i915]
| intel_atomic_commit_tail+0xd55/0x19a0 [i915]
| intel_atomic_commit+0x25d/0x2a0 [i915]
| drm_atomic_commit+0xad/0xe0 [drm]
| intel_initial_commit+0x16c/0x200 [i915]
| intel_display_driver_probe+0x2e/0x80 [i915]
| i915_driver_probe+0x791/0xc10 [i915]
| i915_pci_probe+0xd7/0x190 [i915]

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
---
drivers/gpu/drm/i915/display/intel_display.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 9cfa3fa915cf5..3a0cab5db2490 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -3035,8 +3035,9 @@ void i9xx_set_pipeconf(const struct intel_crtc_state *crtc_state)

val |= TRANSCONF_FRAME_START_DELAY(crtc_state->framestart_delay - 1);

- intel_de_write(display, TRANSCONF(display, cpu_transcoder), val);
- intel_de_posting_read(display, TRANSCONF(display, cpu_transcoder));
+ intel_de_write_fw(display, TRANSCONF(display, cpu_transcoder), val);
+ /* posting read */
+ intel_de_read_fw(display, TRANSCONF(display, cpu_transcoder));
}

static enum intel_output_format
@@ -3231,8 +3232,9 @@ void ilk_set_pipeconf(const struct intel_crtc_state *crtc_state)
val |= TRANSCONF_FRAME_START_DELAY(crtc_state->framestart_delay - 1);
val |= TRANSCONF_MSA_TIMING_DELAY(crtc_state->msa_timing_delay);

- intel_de_write(display, TRANSCONF(display, cpu_transcoder), val);
- intel_de_posting_read(display, TRANSCONF(display, cpu_transcoder));
+ intel_de_write_fw(display, TRANSCONF(display, cpu_transcoder), val);
+ /* posting read */
+ intel_de_read_fw(display, TRANSCONF(display, cpu_transcoder));
}

static void hsw_set_transconf(const struct intel_crtc_state *crtc_state)
--
2.51.0