1 files changed, 344 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_aperture.c b/drivers/gpu/drm/drm_aperture.c
new file mode 100644
index 000000000000..33bf018c3bdf
--- /dev/null
+++ b/drivers/gpu/drm/drm_aperture.c
@@ -0,0 +1,344 @@
+// SPDX-License-Identifier: MIT
+
+#include <linux/device.h>
+#include <linux/fb.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h> /* for firmware helpers */
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/vgaarb.h>
+
+#include <drm/drm_aperture.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_print.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. DRM aperture functions manage
+ * ownership of DRM framebuffer memory and hand-over between drivers.
+ *
+ * DRM drivers should call drm_aperture_remove_conflicting_framebuffers()
+ * at the top of their probe function. The function removes any generic
+ * driver that is currently associated with the given framebuffer memory.
+ * If the framebuffer is located at PCI BAR 0, the rsp code looks as in the
+ * example given below.
+ *
+ * .. code-block:: c
+ *
+ *	static int remove_conflicting_framebuffers(struct pci_dev *pdev)
+ *	{
+ *		bool primary = false;
+ *		resource_size_t base, size;
+ *		int ret;
+ *
+ *		base = pci_resource_start(pdev, 0);
+ *		size = pci_resource_len(pdev, 0);
+ *	#ifdef CONFIG_X86
+ *		primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
+ *	#endif
+ *
+ *		return drm_aperture_remove_conflicting_framebuffers(base, size, primary,
+ *		                                                    "example driver");
+ *	}
+ *
+ *	static int probe(struct pci_dev *pdev)
+ *	{
+ *		int ret;
+ *
+ *		// Remove any generic drivers...
+ *		ret = remove_conflicting_framebuffers(pdev);
+ *		if (ret)
+ *			return ret;
+ *
+ *		// ... and initialize the hardware.
+ *		...
+ *
+ *		drm_dev_register();
+ *
+ *		return 0;
+ *	}
+ *
+ * PCI device drivers should call
+ * drm_aperture_remove_conflicting_pci_framebuffers() and let it detect the
+ * framebuffer apertures automatically. Device drivers without knowledge of
+ * the framebuffer's location shall call drm_aperture_remove_framebuffers(),
+ * which removes all drivers for known framebuffer.
+ *
+ * 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
+ * given framebuffer memory. Ownership of the framebuffer memory is achived
+ * by calling devm_aperture_acquire_from_firmware(). On success, the driver
+ * is the owner of the framebuffer range. The function fails if the
+ * framebuffer is already by another driver. See below for an example.
+ *
+ * .. code-block:: c
+ *
+ *	static int acquire_framebuffers(struct drm_device *dev, struct platform_device *pdev)
+ *	{
+ *		resource_size_t base, size;
+ *
+ *		mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ *		if (!mem)
+ *			return -EINVAL;
+ *		base = mem->start;
+ *		size = resource_size(mem);
+ *
+ *		return devm_acquire_aperture_from_firmware(dev, base, size);
+ *	}
+ *
+ *	static int probe(struct platform_device *pdev)
+ *	{
+ *		struct drm_device *dev;
+ *		int ret;
+ *
+ *		// ... Initialize the device...
+ *		dev = devm_drm_dev_alloc();
+ *		...
+ *
+ *		// ... and acquire ownership of the framebuffer.
+ *		ret = acquire_framebuffers(dev, pdev);
+ *		if (ret)
+ *			return ret;
+ *
+ *		drm_dev_register(dev, 0);
+ *
+ *		return 0;
+ *	}
+ *
+ * The generic driver is now subject to forced removal by other drivers. This
+ * only works for platform drivers that support hot unplug.
+ * When a driver calls drm_aperture_remove_conflicting_framebuffers() et al
+ * for the registered framebuffer range, the aperture helpers call
+ * platform_device_unregister() and the generic driver unloads itself. It
+ * may not access the device's registers, framebuffer memory, ROM, etc
+ * afterwards.
+ */
+
+struct drm_aperture {
+	struct drm_device *dev;
+	resource_size_t base;
+	resource_size_t size;
+	struct list_head lh;
+	void (*detach)(struct drm_device *dev);
+};
+
+static LIST_HEAD(drm_apertures);
+static DEFINE_MUTEX(drm_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 drm_aperture *ap = data;
+	bool detached = !ap->dev;
+
+	if (detached)
+		return;
+
+	mutex_lock(&drm_apertures_lock);
+	list_del(&ap->lh);
+	mutex_unlock(&drm_apertures_lock);
+}
+
+static int devm_aperture_acquire(struct drm_device *dev,
+				 resource_size_t base, resource_size_t size,
+				 void (*detach)(struct drm_device *))
+{
+	size_t end = base + size;
+	struct list_head *pos;
+	struct drm_aperture *ap;
+
+	mutex_lock(&drm_apertures_lock);
+
+	list_for_each(pos, &drm_apertures) {
+		ap = container_of(pos, struct drm_aperture, lh);
+		if (overlap(base, end, ap->base, ap->base + ap->size))
+			return -EBUSY;
+	}
+
+	ap = devm_kzalloc(dev->dev, sizeof(*ap), GFP_KERNEL);
+	if (!ap)
+		return -ENOMEM;
+
+	ap->dev = dev;
+	ap->base = base;
+	ap->size = size;
+	ap->detach = detach;
+	INIT_LIST_HEAD(&ap->lh);
+
+	list_add(&ap->lh, &drm_apertures);
+
+	mutex_unlock(&drm_apertures_lock);
+
+	return devm_add_action_or_reset(dev->dev, devm_aperture_acquire_release, ap);
+}
+
+static void drm_aperture_detach_firmware(struct drm_device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev->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_from_firmware - Acquires ownership of a firmware framebuffer
+ *                                       on behalf of a DRM driver.
+ * @dev:	the DRM device to own the framebuffer memory
+ * @base:	the framebuffer's byte offset in physical memory
+ * @size:	the framebuffer size in bytes
+ *
+ * Installs the given device as the new owner of the framebuffer. The function
+ * expects the framebuffer to be provided by a platform device that has been
+ * set up by firmware. Firmware can be any generic interface, such as EFI,
+ * VESA, VGA, etc. If the native hardware driver takes over ownership of the
+ * framebuffer range, the firmware state gets lost. Aperture helpers will then
+ * unregister the platform device automatically. Acquired apertures are
+ * released automatically if the underlying device goes away.
+ *
+ * The function fails if the framebuffer range, or parts of it, is currently
+ * owned by another driver. To evict current owners, callers should use
+ * drm_aperture_remove_conflicting_framebuffers() et al. before calling this
+ * function. The function also fails if the given device is not a platform
+ * device.
+ *
+ * Returns:
+ * 0 on success, or a negative errno value otherwise.
+ */
+int devm_aperture_acquire_from_firmware(struct drm_device *dev, resource_size_t base,
+					resource_size_t size)
+{
+	if (drm_WARN_ON(dev, !dev_is_platform(dev->dev)))
+		return -EINVAL;
+
+	return devm_aperture_acquire(dev, base, size, drm_aperture_detach_firmware);
+}
+EXPORT_SYMBOL(devm_aperture_acquire_from_firmware);
+
+static void drm_aperture_detach_drivers(resource_size_t base, resource_size_t size)
+{
+	resource_size_t end = base + size;
+	struct list_head *pos, *n;
+
+	mutex_lock(&drm_apertures_lock);
+
+	list_for_each_safe(pos, n, &drm_apertures) {
+		struct drm_aperture *ap =
+			container_of(pos, struct drm_aperture, lh);
+		struct drm_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(&drm_apertures_lock);
+}
+
+/**
+ * drm_aperture_remove_conflicting_framebuffers - remove existing framebuffers in the given range
+ * @base: the aperture's base address in physical memory
+ * @size: aperture size in bytes
+ * @primary: also kick vga16fb if present
+ * @name: requesting driver name
+ *
+ * This function removes graphics device drivers which use memory range described by
+ * @base and @size.
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise
+ */
+int drm_aperture_remove_conflicting_framebuffers(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
+
+	drm_aperture_detach_drivers(base, size);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);
+
+/**
+ * drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices
+ * @pdev: PCI device
+ * @name: requesting driver name
+ *
+ * This function removes graphics device drivers using memory range configured
+ * for any of @pdev's memory bars. The function assumes that PCI device with
+ * shadowed ROM drives a primary display and so kicks out vga16fb.
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise
+ */
+int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev, const char *name)
+{
+	resource_size_t base, size;
+	int bar, ret = 0;
+
+	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);
+		drm_aperture_detach_drivers(base, size);
+	}
+
+	/*
+	 * 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);
+#endif
+	if (ret == 0)
+		ret = vga_remove_vgacon(pdev);
+	return ret;
+}
+EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);