From: Lukas Wunner Date: Wed, 24 Jan 2018 18:35:45 +0000 (+0100) Subject: Revert "apple-gmux: lock iGP IO to protect from vgaarb changes" X-Git-Tag: Ubuntu-4.15.0-11.12~72 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=517ad2c05e65091b9a8f69c89947e76543122f57;p=mirror_ubuntu-bionic-kernel.git Revert "apple-gmux: lock iGP IO to protect from vgaarb changes" BugLink: http://bugs.launchpad.net/bugs/1751131 commit d6fa7588fd7a8def4c747c0c574ce85d453e3788 upstream. Commit 4eebd5a4e726 ("apple-gmux: lock iGP IO to protect from vgaarb changes") amended this driver's ->probe hook to lock decoding of normal (non-legacy) I/O space accesses to the integrated GPU on dual-GPU MacBook Pros. The lock stays in place until the driver is unbound. The change was made to work around an issue with the out-of-tree nvidia graphics driver (available at http://www.nvidia.com/object/unix.html). It contains the following sequence in nvidia/nv.c: #if defined(CONFIG_VGA_ARB) && !defined(NVCPU_PPC64LE) #if defined(VGA_DEFAULT_DEVICE) vga_tryget(VGA_DEFAULT_DEVICE, VGA_RSRC_LEGACY_MASK); #endif vga_set_legacy_decoding(dev, VGA_RSRC_NONE); #endif This code was reported to cause deadlocks with VFIO already in 2013: https://devtalk.nvidia.com/default/topic/545560 I've reported the issue to Nvidia developers once more in 2017: https://www.spinics.net/lists/dri-devel/msg138754.html On the MacBookPro10,1, this code apparently breaks backlight control (which is handled by apple-gmux via an I/O region starting at 0x700), as reported by Petri Hodju: https://bugzilla.kernel.org/show_bug.cgi?id=86121 I tried to replicate Petri's observations on my MacBook9,1, which uses the same Intel Ivy Bridge + Nvidia GeForce GT 650M architecture, to no avail. On my machine apple-gmux' I/O region remains accessible even with the nvidia driver loaded and commit 4eebd5a4e726 reverted. Petri reported that apple-gmux becomes accessible again after a suspend/resume cycle because the BIOS changed the VGA routing on the root port to the Nvidia GPU. Perhaps this is a BIOS issue after all that can be fixed with an update? In any case, the change made by commit 4eebd5a4e726 has turned out to cause two new issues: * Wilfried Klaebe reports a deadlock when launching Xorg because it opens /dev/vga_arbiter and calls vga_get(), but apple-gmux is holding a lock on I/O space indefinitely. It looks like apple-gmux' current behavior is an abuse of the vgaarb API as locks are not meant to be held for longer periods: https://bugzilla.kernel.org/show_bug.cgi?id=88861#c11 https://bugzilla.kernel.org/attachment.cgi?id=217541 * On dual GPU MacBook Pros introduced since 2013, the integrated GPU is powergated on boot und thus becomes invisible to Linux unless a custom EFI protocol is used to leave it powered on. (A patch exists but is not in mainline yet due to several negative side effects.) On these machines, locking I/O to the integrated GPU (as done by 4eebd5a4e726) fails and backlight control is therefore broken: https://bugzilla.kernel.org/show_bug.cgi?id=105051 So let's revert commit 4eebd5a4e726 please. Users experiencing the issue with the proprietary nvidia driver can comment out the above- quoted problematic code as a workaround (or try updating the BIOS). Cc: Petri Hodju Cc: Bjorn Helgaas Cc: Bruno Prémont Cc: Andy Ritger Cc: Ronald Tschalär Tested-by: Wilfried Klaebe Signed-off-by: Lukas Wunner Cc: stable@vger.kernel.org Signed-off-by: Darren Hart (VMware) Signed-off-by: Greg Kroah-Hartman Signed-off-by: Seth Forshee --- diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c index 623d322447a2..7c4eb86c851e 100644 --- a/drivers/platform/x86/apple-gmux.c +++ b/drivers/platform/x86/apple-gmux.c @@ -24,7 +24,6 @@ #include #include #include -#include #include #include @@ -54,7 +53,6 @@ struct apple_gmux_data { bool indexed; struct mutex index_lock; - struct pci_dev *pdev; struct backlight_device *bdev; /* switcheroo data */ @@ -599,23 +597,6 @@ static int gmux_resume(struct device *dev) return 0; } -static struct pci_dev *gmux_get_io_pdev(void) -{ - struct pci_dev *pdev = NULL; - - while ((pdev = pci_get_class(PCI_CLASS_DISPLAY_VGA << 8, pdev))) { - u16 cmd; - - pci_read_config_word(pdev, PCI_COMMAND, &cmd); - if (!(cmd & PCI_COMMAND_IO)) - continue; - - return pdev; - } - - return NULL; -} - static int is_thunderbolt(struct device *dev, void *data) { return to_pci_dev(dev)->is_thunderbolt; @@ -631,7 +612,6 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id) int ret = -ENXIO; acpi_status status; unsigned long long gpe; - struct pci_dev *pdev = NULL; if (apple_gmux_data) return -EBUSY; @@ -682,7 +662,7 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id) ver_minor = (version >> 16) & 0xff; ver_release = (version >> 8) & 0xff; } else { - pr_info("gmux device not present or IO disabled\n"); + pr_info("gmux device not present\n"); ret = -ENODEV; goto err_release; } @@ -690,23 +670,6 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id) pr_info("Found gmux version %d.%d.%d [%s]\n", ver_major, ver_minor, ver_release, (gmux_data->indexed ? "indexed" : "classic")); - /* - * Apple systems with gmux are EFI based and normally don't use - * VGA. In addition changing IO+MEM ownership between IGP and dGPU - * disables IO/MEM used for backlight control on some systems. - * Lock IO+MEM to GPU with active IO to prevent switch. - */ - pdev = gmux_get_io_pdev(); - if (pdev && vga_tryget(pdev, - VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM)) { - pr_err("IO+MEM vgaarb-locking for PCI:%s failed\n", - pci_name(pdev)); - ret = -EBUSY; - goto err_release; - } else if (pdev) - pr_info("locked IO for PCI:%s\n", pci_name(pdev)); - gmux_data->pdev = pdev; - memset(&props, 0, sizeof(props)); props.type = BACKLIGHT_PLATFORM; props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS); @@ -822,10 +785,6 @@ err_enable_gpe: err_notify: backlight_device_unregister(bdev); err_release: - if (gmux_data->pdev) - vga_put(gmux_data->pdev, - VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM); - pci_dev_put(pdev); release_region(gmux_data->iostart, gmux_data->iolen); err_free: kfree(gmux_data); @@ -845,11 +804,6 @@ static void gmux_remove(struct pnp_dev *pnp) &gmux_notify_handler); } - if (gmux_data->pdev) { - vga_put(gmux_data->pdev, - VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM); - pci_dev_put(gmux_data->pdev); - } backlight_device_unregister(gmux_data->bdev); release_region(gmux_data->iostart, gmux_data->iolen);