1 files changed, 47 insertions, 1 deletions

diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
index 66d6d22c239c..6808715003f6 100644
--- a/drivers/platform/x86/apple-gmux.c
+++ b/drivers/platform/x86/apple-gmux.c
@@ -22,6 +22,7 @@
 #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>
 
@@ -31,6 +32,7 @@ struct apple_gmux_data {
         bool indexed;
         struct mutex index_lock;
 
+        struct pci_dev *pdev;
         struct backlight_device *bdev;
 
         /* switcheroo data */
@@ -415,6 +417,23 @@ 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 gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
 {
         struct apple_gmux_data *gmux_data;
@@ -425,6 +444,7 @@ 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;
@@ -475,7 +495,7 @@ 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\n");
+                        pr_info("gmux device not present or IO disabled\n");
                         ret = -ENODEV;
                         goto err_release;
                 }
@@ -483,6 +503,23 @@ 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);
@@ -574,6 +611,10 @@ 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);
@@ -593,6 +634,11 @@ 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);