3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: Lukas Wunner lukas@wunner.de
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 petrihodju@yahoo.com Cc: Bjorn Helgaas bhelgaas@google.com Cc: Bruno Prémont bonbons@linux-vserver.org Cc: Andy Ritger aritger@nvidia.com Cc: Ronald Tschalär ronald@innovation.ch Tested-by: Wilfried Klaebe linux-kernel@lebenslange-mailadresse.de Signed-off-by: Lukas Wunner lukas@wunner.de Signed-off-by: Darren Hart (VMware) dvhart@infradead.org [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/platform/x86/apple-gmux.c | 48 +------------------------------ 1 file changed, 1 insertion(+), 47 deletions(-)
--- a/drivers/platform/x86/apple-gmux.c +++ b/drivers/platform/x86/apple-gmux.c @@ -22,7 +22,6 @@ #include <linux/delay.h> #include <linux/pci.h> #include <linux/vga_switcheroo.h> -#include <linux/vgaarb.h> #include <acpi/video.h> #include <asm/io.h>
@@ -32,7 +31,6 @@ struct apple_gmux_data { bool indexed; struct mutex index_lock;
- struct pci_dev *pdev; struct backlight_device *bdev;
/* switcheroo data */ @@ -417,23 +415,6 @@ static int gmux_resume(struct device *de 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 gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id) { struct apple_gmux_data *gmux_data; @@ -444,7 +425,6 @@ static int gmux_probe(struct pnp_dev *pn int ret = -ENXIO; acpi_status status; unsigned long long gpe; - struct pci_dev *pdev = NULL;
if (apple_gmux_data) return -EBUSY; @@ -495,7 +475,7 @@ static int gmux_probe(struct pnp_dev *pn 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; } @@ -503,23 +483,6 @@ static int gmux_probe(struct pnp_dev *pn 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); @@ -611,10 +574,6 @@ 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); @@ -634,11 +593,6 @@ static void gmux_remove(struct pnp_dev * &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);