1 files changed, 351 insertions, 0 deletions
diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
new file mode 100644
index 000000000000..538f2d40acda
--- /dev/null
+++ b/drivers/video/aperture.c
@@ -0,0 +1,351 @@
+// SPDX-License-Identifier: MIT
+
+#include <linux/aperture.h>
+#include <linux/device.h>
+#include <linux/fb.h> /* for old fbdev helpers */
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/vgaarb.h>
+
+/**
+ * DOC: overview
+ *
+ * A graphics device might be supported by different drivers, but only one
+ * driver can be active at any given time. Many systems load a generic
+ * graphics drivers, such as EFI-GOP or VESA, early during the boot process.
+ * During later boot stages, they replace the generic driver with a dedicated,
+ * hardware-specific driver. To take over the device the dedicated driver
+ * first has to remove the generic driver. Aperture functions manage
+ * ownership of framebuffer memory and hand-over between drivers.
+ *
+ * Graphics drivers should call aperture_remove_conflicting_devices()
+ * at the top of their probe function. The function removes any generic
+ * driver that is currently associated with the given framebuffer memory.
+ * An example for a graphics device on the platform bus is shown below.
+ *
+ * .. code-block:: c
+ *
+ *	static int example_probe(struct platform_device *pdev)
+ *	{
+ *		struct resource *mem;
+ *		resource_size_t base, size;
+ *		int ret;
+ *
+ *		mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ *		if (!mem)
+ *			return -ENODEV;
+ *		base = mem->start;
+ *		size = resource_size(mem);
+ *
+ *		ret = aperture_remove_conflicting_devices(base, size, false, "example");
+ *		if (ret)
+ *			return ret;
+ *
+ *		// Initialize the hardware
+ *		...
+ *
+ *		return 0;
+ *	}
+ *
+ *	static const struct platform_driver example_driver = {
+ *		.probe = example_probe,
+ *		...
+ *	};
+ *
+ * The given example reads the platform device's I/O-memory range from the
+ * device instance. An active framebuffer will be located within this range.
+ * The call to aperture_remove_conflicting_devices() releases drivers that
+ * have previously claimed ownership of the range and are currently driving
+ * output on the framebuffer. If successful, the new driver can take over
+ * the device.
+ *
+ * While the given example uses a platform device, the aperture helpers work
+ * with every bus that has an addressable framebuffer. In the case of PCI,
+ * device drivers can also call aperture_remove_conflicting_pci_devices() and
+ * let the function detect the apertures automatically. Device drivers without
+ * knowledge of the framebuffer's location can call
+ * aperture_remove_all_conflicting_devices(), which removes all known devices.
+ *
+ * Drivers that are susceptible to being removed by other drivers, such as
+ * generic EFI or VESA drivers, have to register themselves as owners of their
+ * framebuffer apertures. Ownership of the framebuffer memory is achieved
+ * by calling devm_aperture_acquire_for_platform_device(). If successful, the
+ * driveris the owner of the framebuffer range. The function fails if the
+ * framebuffer is already owned by another driver. See below for an example.
+ *
+ * .. code-block:: c
+ *
+ *	static int generic_probe(struct platform_device *pdev)
+ *	{
+ *		struct resource *mem;
+ *		resource_size_t base, size;
+ *
+ *		mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ *		if (!mem)
+ *			return -ENODEV;
+ *		base = mem->start;
+ *		size = resource_size(mem);
+ *
+ *		ret = devm_aperture_acquire_for_platform_device(pdev, base, size);
+ *		if (ret)
+ *			return ret;
+ *
+ *		// Initialize the hardware
+ *		...
+ *
+ *		return 0;
+ *	}
+ *
+ *	static int generic_remove(struct platform_device *)
+ *	{
+ *		// Hot-unplug the device
+ *		...
+ *
+ *		return 0;
+ *	}
+ *
+ *	static const struct platform_driver generic_driver = {
+ *		.probe = generic_probe,
+ *		.remove = generic_remove,
+ *		...
+ *	};
+ *
+ * The similar to the previous example, the generic driver claims ownership
+ * of the framebuffer memory from its probe function. This will fail if the
+ * memory range, or parts of it, is already owned by another driver.
+ *
+ * If successful, the generic driver is now subject to forced removal by
+ * another driver. This only works for platform drivers that support hot
+ * unplugging. When a driver calls aperture_remove_conflicting_devices()
+ * et al for the registered framebuffer range, the aperture helpers call
+ * platform_device_unregister() and the generic driver unloads itself. The
+ * generic driver also has to provide a remove function to make this work.
+ * Once hot unplugged fro mhardware, it may not access the device's
+ * registers, framebuffer memory, ROM, etc afterwards.
+ */
+
+struct aperture_range {
+	struct device *dev;
+	resource_size_t base;
+	resource_size_t size;
+	struct list_head lh;
+	void (*detach)(struct device *dev);
+};
+
+static LIST_HEAD(apertures);
+static DEFINE_MUTEX(apertures_lock);
+
+static bool overlap(resource_size_t base1, resource_size_t end1,
+		    resource_size_t base2, resource_size_t end2)
+{
+	return (base1 < end2) && (end1 > base2);
+}
+
+static void devm_aperture_acquire_release(void *data)
+{
+	struct aperture_range *ap = data;
+	bool detached = !ap->dev;
+
+	if (detached)
+		return;
+
+	mutex_lock(&apertures_lock);
+	list_del(&ap->lh);
+	mutex_unlock(&apertures_lock);
+}
+
+static int devm_aperture_acquire(struct device *dev,
+				 resource_size_t base, resource_size_t size,
+				 void (*detach)(struct device *))
+{
+	size_t end = base + size;
+	struct list_head *pos;
+	struct aperture_range *ap;
+
+	mutex_lock(&apertures_lock);
+
+	list_for_each(pos, &apertures) {
+		ap = container_of(pos, struct aperture_range, lh);
+		if (overlap(base, end, ap->base, ap->base + ap->size)) {
+			mutex_unlock(&apertures_lock);
+			return -EBUSY;
+		}
+	}
+
+	ap = devm_kzalloc(dev, sizeof(*ap), GFP_KERNEL);
+	if (!ap) {
+		mutex_unlock(&apertures_lock);
+		return -ENOMEM;
+	}
+
+	ap->dev = dev;
+	ap->base = base;
+	ap->size = size;
+	ap->detach = detach;
+	INIT_LIST_HEAD(&ap->lh);
+
+	list_add(&ap->lh, &apertures);
+
+	mutex_unlock(&apertures_lock);
+
+	return devm_add_action_or_reset(dev, devm_aperture_acquire_release, ap);
+}
+
+static void aperture_detach_platform_device(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+
+	/*
+	 * Remove the device from the device hierarchy. This is the right thing
+	 * to do for firmware-based DRM drivers, such as EFI, VESA or VGA. After
+	 * the new driver takes over the hardware, the firmware device's state
+	 * will be lost.
+	 *
+	 * For non-platform devices, a new callback would be required.
+	 *
+	 * If the aperture helpers ever need to handle native drivers, this call
+	 * would only have to unplug the DRM device, so that the hardware device
+	 * stays around after detachment.
+	 */
+	platform_device_unregister(pdev);
+}
+
+/**
+ * devm_aperture_acquire_for_platform_device - Acquires ownership of an aperture
+ *                                             on behalf of a platform device.
+ * @pdev:	the platform device to own the aperture
+ * @base:	the aperture's byte offset in physical memory
+ * @size:	the aperture size in bytes
+ *
+ * Installs the given device as the new owner of the aperture. The function
+ * expects the aperture to be provided by a platform device. If another
+ * driver takes over ownership of the aperture, aperture helpers will then
+ * unregister the platform device automatically. All acquired apertures are
+ * released automatically when the underlying device goes away.
+ *
+ * The function fails if the aperture, or parts of it, is currently
+ * owned by another device. To evict current owners, callers should use
+ * remove_conflicting_devices() et al. before calling this function.
+ *
+ * Returns:
+ * 0 on success, or a negative errno value otherwise.
+ */
+int devm_aperture_acquire_for_platform_device(struct platform_device *pdev,
+					      resource_size_t base,
+					      resource_size_t size)
+{
+	return devm_aperture_acquire(&pdev->dev, base, size, aperture_detach_platform_device);
+}
+EXPORT_SYMBOL(devm_aperture_acquire_for_platform_device);
+
+static void aperture_detach_devices(resource_size_t base, resource_size_t size)
+{
+	resource_size_t end = base + size;
+	struct list_head *pos, *n;
+
+	mutex_lock(&apertures_lock);
+
+	list_for_each_safe(pos, n, &apertures) {
+		struct aperture_range *ap = container_of(pos, struct aperture_range, lh);
+		struct device *dev = ap->dev;
+
+		if (WARN_ON_ONCE(!dev))
+			continue;
+
+		if (!overlap(base, end, ap->base, ap->base + ap->size))
+			continue;
+
+		ap->dev = NULL; /* detach from device */
+		list_del(&ap->lh);
+
+		ap->detach(dev);
+	}
+
+	mutex_unlock(&apertures_lock);
+}
+
+/**
+ * aperture_remove_conflicting_devices - remove devices in the given range
+ * @base: the aperture's base address in physical memory
+ * @size: aperture size in bytes
+ * @primary: also kick vga16fb if present; only relevant for VGA devices
+ * @name: a descriptive name of the requesting driver
+ *
+ * This function removes devices that own apertures within @base and @size.
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise
+ */
+int aperture_remove_conflicting_devices(resource_size_t base, resource_size_t size,
+					bool primary, const char *name)
+{
+#if IS_REACHABLE(CONFIG_FB)
+	struct apertures_struct *a;
+	int ret;
+
+	a = alloc_apertures(1);
+	if (!a)
+		return -ENOMEM;
+
+	a->ranges[0].base = base;
+	a->ranges[0].size = size;
+
+	ret = remove_conflicting_framebuffers(a, name, primary);
+	kfree(a);
+
+	if (ret)
+		return ret;
+#endif
+
+	aperture_detach_devices(base, size);
+
+	return 0;
+}
+EXPORT_SYMBOL(aperture_remove_conflicting_devices);
+
+/**
+ * aperture_remove_conflicting_pci_devices - remove existing framebuffers for PCI devices
+ * @pdev: PCI device
+ * @name: a descriptive name of the requesting driver
+ *
+ * This function removes devices that own apertures within any of @pdev's
+ * memory bars. The function assumes that PCI device with shadowed ROM
+ * drives a primary display and therefore kicks out vga16fb as well.
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise
+ */
+int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *name)
+{
+	resource_size_t base, size;
+	int bar, ret;
+
+	/*
+	 * WARNING: Apparently we must kick fbdev drivers before vgacon,
+	 * otherwise the vga fbdev driver falls over.
+	 */
+#if IS_REACHABLE(CONFIG_FB)
+	ret = remove_conflicting_pci_framebuffers(pdev, name);
+	if (ret)
+		return ret;
+#endif
+	ret = vga_remove_vgacon(pdev);
+	if (ret)
+		return ret;
+
+	for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
+		if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
+			continue;
+		base = pci_resource_start(pdev, bar);
+		size = pci_resource_len(pdev, bar);
+		aperture_detach_devices(base, size);
+	}
+
+	return 0;
+
+}
+EXPORT_SYMBOL(aperture_remove_conflicting_pci_devices);