360 lines
11 KiB
C
360 lines
11 KiB
C
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// SPDX-License-Identifier: MIT
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#include <linux/aperture.h>
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#include <linux/device.h>
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#include <linux/list.h>
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#include <linux/mutex.h>
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#include <linux/pci.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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#include <linux/sysfb.h>
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#include <linux/types.h>
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#include <linux/vgaarb.h>
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#include <video/vga.h>
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/**
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* DOC: overview
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*
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* A graphics device might be supported by different drivers, but only one
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* driver can be active at any given time. Many systems load a generic
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* graphics drivers, such as EFI-GOP or VESA, early during the boot process.
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* During later boot stages, they replace the generic driver with a dedicated,
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* hardware-specific driver. To take over the device the dedicated driver
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* first has to remove the generic driver. Aperture functions manage
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* ownership of framebuffer memory and hand-over between drivers.
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*
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* Graphics drivers should call aperture_remove_conflicting_devices()
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* at the top of their probe function. The function removes any generic
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* driver that is currently associated with the given framebuffer memory.
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* An example for a graphics device on the platform bus is shown below.
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*
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* .. code-block:: c
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*
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* static int example_probe(struct platform_device *pdev)
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* {
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* struct resource *mem;
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* resource_size_t base, size;
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* int ret;
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*
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* mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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* if (!mem)
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* return -ENODEV;
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* base = mem->start;
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* size = resource_size(mem);
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*
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* ret = aperture_remove_conflicting_devices(base, size, false, "example");
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* if (ret)
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* return ret;
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*
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* // Initialize the hardware
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* ...
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*
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* return 0;
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* }
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*
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* static const struct platform_driver example_driver = {
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* .probe = example_probe,
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* ...
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* };
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*
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* The given example reads the platform device's I/O-memory range from the
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* device instance. An active framebuffer will be located within this range.
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* The call to aperture_remove_conflicting_devices() releases drivers that
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* have previously claimed ownership of the range and are currently driving
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* output on the framebuffer. If successful, the new driver can take over
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* the device.
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*
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* While the given example uses a platform device, the aperture helpers work
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* with every bus that has an addressable framebuffer. In the case of PCI,
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* device drivers can also call aperture_remove_conflicting_pci_devices() and
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* let the function detect the apertures automatically. Device drivers without
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* knowledge of the framebuffer's location can call
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* aperture_remove_all_conflicting_devices(), which removes all known devices.
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*
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* Drivers that are susceptible to being removed by other drivers, such as
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* generic EFI or VESA drivers, have to register themselves as owners of their
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* framebuffer apertures. Ownership of the framebuffer memory is achieved
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* by calling devm_aperture_acquire_for_platform_device(). If successful, the
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* driveris the owner of the framebuffer range. The function fails if the
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* framebuffer is already owned by another driver. See below for an example.
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*
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* .. code-block:: c
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*
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* static int generic_probe(struct platform_device *pdev)
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* {
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* struct resource *mem;
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* resource_size_t base, size;
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*
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* mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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* if (!mem)
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* return -ENODEV;
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* base = mem->start;
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* size = resource_size(mem);
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*
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* ret = devm_aperture_acquire_for_platform_device(pdev, base, size);
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* if (ret)
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* return ret;
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*
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* // Initialize the hardware
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* ...
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*
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* return 0;
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* }
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*
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* static int generic_remove(struct platform_device *)
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* {
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* // Hot-unplug the device
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* ...
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*
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* return 0;
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* }
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*
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* static const struct platform_driver generic_driver = {
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* .probe = generic_probe,
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* .remove = generic_remove,
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* ...
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* };
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*
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* The similar to the previous example, the generic driver claims ownership
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* of the framebuffer memory from its probe function. This will fail if the
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* memory range, or parts of it, is already owned by another driver.
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*
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* If successful, the generic driver is now subject to forced removal by
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* another driver. This only works for platform drivers that support hot
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* unplugging. When a driver calls aperture_remove_conflicting_devices()
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* et al for the registered framebuffer range, the aperture helpers call
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* platform_device_unregister() and the generic driver unloads itself. The
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* generic driver also has to provide a remove function to make this work.
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* Once hot unplugged fro mhardware, it may not access the device's
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* registers, framebuffer memory, ROM, etc afterwards.
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*/
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struct aperture_range {
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struct device *dev;
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resource_size_t base;
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resource_size_t size;
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struct list_head lh;
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void (*detach)(struct device *dev);
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};
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static LIST_HEAD(apertures);
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static DEFINE_MUTEX(apertures_lock);
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static bool overlap(resource_size_t base1, resource_size_t end1,
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resource_size_t base2, resource_size_t end2)
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{
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return (base1 < end2) && (end1 > base2);
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}
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static void devm_aperture_acquire_release(void *data)
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{
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struct aperture_range *ap = data;
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bool detached = !ap->dev;
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if (detached)
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return;
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mutex_lock(&apertures_lock);
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list_del(&ap->lh);
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mutex_unlock(&apertures_lock);
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}
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static int devm_aperture_acquire(struct device *dev,
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resource_size_t base, resource_size_t size,
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void (*detach)(struct device *))
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{
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size_t end = base + size;
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struct list_head *pos;
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struct aperture_range *ap;
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mutex_lock(&apertures_lock);
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list_for_each(pos, &apertures) {
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ap = container_of(pos, struct aperture_range, lh);
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if (overlap(base, end, ap->base, ap->base + ap->size)) {
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mutex_unlock(&apertures_lock);
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return -EBUSY;
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}
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}
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ap = devm_kzalloc(dev, sizeof(*ap), GFP_KERNEL);
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if (!ap) {
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mutex_unlock(&apertures_lock);
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return -ENOMEM;
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}
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ap->dev = dev;
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ap->base = base;
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ap->size = size;
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ap->detach = detach;
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INIT_LIST_HEAD(&ap->lh);
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list_add(&ap->lh, &apertures);
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mutex_unlock(&apertures_lock);
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return devm_add_action_or_reset(dev, devm_aperture_acquire_release, ap);
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}
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static void aperture_detach_platform_device(struct device *dev)
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{
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struct platform_device *pdev = to_platform_device(dev);
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/*
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* Remove the device from the device hierarchy. This is the right thing
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* to do for firmware-based DRM drivers, such as EFI, VESA or VGA. After
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* the new driver takes over the hardware, the firmware device's state
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* will be lost.
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*
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* For non-platform devices, a new callback would be required.
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*
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* If the aperture helpers ever need to handle native drivers, this call
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* would only have to unplug the DRM device, so that the hardware device
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* stays around after detachment.
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*/
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platform_device_unregister(pdev);
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}
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/**
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* devm_aperture_acquire_for_platform_device - Acquires ownership of an aperture
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* on behalf of a platform device.
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* @pdev: the platform device to own the aperture
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* @base: the aperture's byte offset in physical memory
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* @size: the aperture size in bytes
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*
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* Installs the given device as the new owner of the aperture. The function
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* expects the aperture to be provided by a platform device. If another
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* driver takes over ownership of the aperture, aperture helpers will then
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* unregister the platform device automatically. All acquired apertures are
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* released automatically when the underlying device goes away.
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*
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* The function fails if the aperture, or parts of it, is currently
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* owned by another device. To evict current owners, callers should use
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* remove_conflicting_devices() et al. before calling this function.
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*
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* Returns:
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* 0 on success, or a negative errno value otherwise.
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*/
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int devm_aperture_acquire_for_platform_device(struct platform_device *pdev,
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resource_size_t base,
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resource_size_t size)
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{
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return devm_aperture_acquire(&pdev->dev, base, size, aperture_detach_platform_device);
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}
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EXPORT_SYMBOL(devm_aperture_acquire_for_platform_device);
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static void aperture_detach_devices(resource_size_t base, resource_size_t size)
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{
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resource_size_t end = base + size;
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struct list_head *pos, *n;
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mutex_lock(&apertures_lock);
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list_for_each_safe(pos, n, &apertures) {
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struct aperture_range *ap = container_of(pos, struct aperture_range, lh);
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struct device *dev = ap->dev;
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if (WARN_ON_ONCE(!dev))
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continue;
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if (!overlap(base, end, ap->base, ap->base + ap->size))
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continue;
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ap->dev = NULL; /* detach from device */
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list_del(&ap->lh);
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ap->detach(dev);
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}
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mutex_unlock(&apertures_lock);
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}
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/**
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* aperture_remove_conflicting_devices - remove devices in the given range
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* @base: the aperture's base address in physical memory
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* @size: aperture size in bytes
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* @primary: also kick vga16fb if present; only relevant for VGA devices
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* @name: a descriptive name of the requesting driver
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*
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* This function removes devices that own apertures within @base and @size.
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*
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* Returns:
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* 0 on success, or a negative errno code otherwise
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*/
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int aperture_remove_conflicting_devices(resource_size_t base, resource_size_t size,
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bool primary, const char *name)
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{
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/*
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* If a driver asked to unregister a platform device registered by
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* sysfb, then can be assumed that this is a driver for a display
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* that is set up by the system firmware and has a generic driver.
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*
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* Drivers for devices that don't have a generic driver will never
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* ask for this, so let's assume that a real driver for the display
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* was already probed and prevent sysfb to register devices later.
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*/
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sysfb_disable();
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aperture_detach_devices(base, size);
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return 0;
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}
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EXPORT_SYMBOL(aperture_remove_conflicting_devices);
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/**
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* aperture_remove_conflicting_pci_devices - remove existing framebuffers for PCI devices
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* @pdev: PCI device
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* @name: a descriptive name of the requesting driver
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*
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* This function removes devices that own apertures within any of @pdev's
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* memory bars. The function assumes that PCI device with shadowed ROM
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* drives a primary display and therefore kicks out vga16fb as well.
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*
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* Returns:
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* 0 on success, or a negative errno code otherwise
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*/
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int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *name)
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{
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bool primary = false;
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resource_size_t base, size;
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int bar, ret;
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#ifdef CONFIG_X86
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primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
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#endif
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if (primary)
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sysfb_disable();
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for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
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if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
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continue;
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base = pci_resource_start(pdev, bar);
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size = pci_resource_len(pdev, bar);
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aperture_detach_devices(base, size);
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}
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if (primary) {
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/*
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* If this is the primary adapter, there could be a VGA device
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* that consumes the VGA framebuffer I/O range. Remove this
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* device as well.
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*/
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aperture_detach_devices(VGA_FB_PHYS_BASE, VGA_FB_PHYS_SIZE);
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/*
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* WARNING: Apparently we must kick fbdev drivers before vgacon,
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* otherwise the vga fbdev driver falls over.
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*/
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ret = vga_remove_vgacon(pdev);
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if (ret)
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return ret;
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}
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return 0;
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}
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EXPORT_SYMBOL(aperture_remove_conflicting_pci_devices);
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