[Bug 105637] i915 crashes MacBook2,1 with commit 23ac12732825901b3fc6ac720958d8bff9a0d6ec (4.15)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105637

--- Comment #29 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
Is there an ethernet port on the machine by any change?

If yes, netconsole should be capable of giving us more of the dmesg.

If no, maybe someting like this would let you catch more of the debug output
before the hang:
diff --git a/drivers/gpu/drm/i915/intel_display.c
b/drivers/gpu/drm/i915/intel_display.c
index c13b2f5704b6..3cc0df6b5ebe 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -16164,6 +16164,8 @@ intel_modeset_setup_hw_state(struct drm_device *dev,
        /* HW state is read out, now we need to sanitize this mess. */
        get_encoder_power_domains(dev_priv);

+       msleep(5000);
+
        intel_sanitize_plane_mapping(dev_priv);

        for_each_intel_encoder(dev, encoder) {


One peculiar thing about the good logs is that there are no planes enabled when
we initialize the driver. That would suggest that it's using the VGA plane,
which is rather odd considering it's supposed to be using EFI.

This should tells whether the VGA plane is enabled or not:
diff --git a/drivers/gpu/drm/i915/intel_display.c
b/drivers/gpu/drm/i915/intel_display.c
index c13b2f5704b6..0e976dd2535f 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15311,10 +15311,13 @@ static void i915_disable_vga(struct drm_i915_private
*dev_priv)
        u8 sr1;
        i915_reg_t vga_reg = i915_vgacntrl_reg(dev_priv);

+       DRM_DEBUG_KMS("VGA = 0x%08x\n", I915_READ(vga_reg));
+
        /* WaEnableVGAAccessThroughIOPort:ctg,elk,ilk,snb,ivb,vlv,hsw */
        vga_get_uninterruptible(pdev, VGA_RSRC_LEGACY_IO);
        outb(SR01, VGA_SR_INDEX);
        sr1 = inb(VGA_SR_DATA);
+       DRM_DEBUG_KMS("SR1 = 0x%02x\n", sr1);
        outb(sr1 | 1<<5, VGA_SR_DATA);
        vga_put(pdev, VGA_RSRC_LEGACY_IO);
        udelay(300);

Another peculiarity are the !connector_state->crtc warns. Not sure what is
causing those. Maybe the whole thing was just busted back then.

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