gmux is a microcontroller built into dual GPU MacBook Pros. On pre-retina MBPs, if we're the inactive GPU, we need apple-gmux to temporarily switch DDC so that we can probe the panel's EDID.
The checks for CONFIG_VGA_ARB and CONFIG_VGA_SWITCHEROO are necessary because if either of them is disabled but gmux is present, the driver would never load, even if we're the active GPU. (vga_default_device() would evaluate to NULL and vga_switcheroo_handler_flags() would evaluate to 0.) Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=88861 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=61115 Tested-by: Lukas Wunner <lukas at wunner.de> [MBP 9,1 2012 intel IVB + nvidia GK107 pre-retina 15"] Signed-off-by: Lukas Wunner <lukas at wunner.de> --- drivers/gpu/drm/i915/i915_drv.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c index 3ac616d..4a5fc5d 100644 --- a/drivers/gpu/drm/i915/i915_drv.c +++ b/drivers/gpu/drm/i915/i915_drv.c @@ -35,9 +35,12 @@ #include "i915_trace.h" #include "intel_drv.h" +#include <linux/apple-gmux.h> #include <linux/console.h> #include <linux/module.h> #include <linux/pm_runtime.h> +#include <linux/vgaarb.h> +#include <linux/vga_switcheroo.h> #include <drm/drm_crtc_helper.h> static struct drm_driver driver; @@ -967,6 +970,15 @@ static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent) if (PCI_FUNC(pdev->devfn)) return -ENODEV; + /* + * apple-gmux is needed on dual GPU MacBook Pro + * to probe the panel if we're the inactive GPU. + */ + if (IS_ENABLED(CONFIG_VGA_ARB) && IS_ENABLED(CONFIG_VGA_SWITCHEROO) && + apple_gmux_present() && pdev != vga_default_device() && + !vga_switcheroo_handler_flags()) + return -EPROBE_DEFER; + return drm_get_pci_dev(pdev, ent, &driver); } -- 1.8.5.2 (Apple Git-48)
