193 lines · c
1// SPDX-License-Identifier: MIT2 3#include <linux/aperture.h>4#include <linux/platform_device.h>5 6#include <drm/drm_aperture.h>7#include <drm/drm_drv.h>8#include <drm/drm_print.h>9 10/**11 * DOC: overview12 *13 * A graphics device might be supported by different drivers, but only one14 * driver can be active at any given time. Many systems load a generic15 * graphics drivers, such as EFI-GOP or VESA, early during the boot process.16 * During later boot stages, they replace the generic driver with a dedicated,17 * hardware-specific driver. To take over the device the dedicated driver18 * first has to remove the generic driver. DRM aperture functions manage19 * ownership of DRM framebuffer memory and hand-over between drivers.20 *21 * DRM drivers should call drm_aperture_remove_conflicting_framebuffers()22 * at the top of their probe function. The function removes any generic23 * driver that is currently associated with the given framebuffer memory.24 * If the framebuffer is located at PCI BAR 0, the rsp code looks as in the25 * example given below.26 *27 * .. code-block:: c28 *29 * static const struct drm_driver example_driver = {30 * ...31 * };32 *33 * static int remove_conflicting_framebuffers(struct pci_dev *pdev)34 * {35 * resource_size_t base, size;36 * int ret;37 *38 * base = pci_resource_start(pdev, 0);39 * size = pci_resource_len(pdev, 0);40 *41 * return drm_aperture_remove_conflicting_framebuffers(base, size,42 * &example_driver);43 * }44 *45 * static int probe(struct pci_dev *pdev)46 * {47 * int ret;48 *49 * // Remove any generic drivers...50 * ret = remove_conflicting_framebuffers(pdev);51 * if (ret)52 * return ret;53 *54 * // ... and initialize the hardware.55 * ...56 *57 * drm_dev_register();58 *59 * return 0;60 * }61 *62 * PCI device drivers should call63 * drm_aperture_remove_conflicting_pci_framebuffers() and let it detect the64 * framebuffer apertures automatically. Device drivers without knowledge of65 * the framebuffer's location shall call drm_aperture_remove_framebuffers(),66 * which removes all drivers for known framebuffer.67 *68 * Drivers that are susceptible to being removed by other drivers, such as69 * generic EFI or VESA drivers, have to register themselves as owners of their70 * given framebuffer memory. Ownership of the framebuffer memory is achieved71 * by calling devm_aperture_acquire_from_firmware(). On success, the driver72 * is the owner of the framebuffer range. The function fails if the73 * framebuffer is already owned by another driver. See below for an example.74 *75 * .. code-block:: c76 *77 * static int acquire_framebuffers(struct drm_device *dev, struct platform_device *pdev)78 * {79 * resource_size_t base, size;80 *81 * mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);82 * if (!mem)83 * return -EINVAL;84 * base = mem->start;85 * size = resource_size(mem);86 *87 * return devm_acquire_aperture_from_firmware(dev, base, size);88 * }89 *90 * static int probe(struct platform_device *pdev)91 * {92 * struct drm_device *dev;93 * int ret;94 *95 * // ... Initialize the device...96 * dev = devm_drm_dev_alloc();97 * ...98 *99 * // ... and acquire ownership of the framebuffer.100 * ret = acquire_framebuffers(dev, pdev);101 * if (ret)102 * return ret;103 *104 * drm_dev_register(dev, 0);105 *106 * return 0;107 * }108 *109 * The generic driver is now subject to forced removal by other drivers. This110 * only works for platform drivers that support hot unplug.111 * When a driver calls drm_aperture_remove_conflicting_framebuffers() et al.112 * for the registered framebuffer range, the aperture helpers call113 * platform_device_unregister() and the generic driver unloads itself. It114 * may not access the device's registers, framebuffer memory, ROM, etc115 * afterwards.116 */117 118/**119 * devm_aperture_acquire_from_firmware - Acquires ownership of a firmware framebuffer120 * on behalf of a DRM driver.121 * @dev: the DRM device to own the framebuffer memory122 * @base: the framebuffer's byte offset in physical memory123 * @size: the framebuffer size in bytes124 *125 * Installs the given device as the new owner of the framebuffer. The function126 * expects the framebuffer to be provided by a platform device that has been127 * set up by firmware. Firmware can be any generic interface, such as EFI,128 * VESA, VGA, etc. If the native hardware driver takes over ownership of the129 * framebuffer range, the firmware state gets lost. Aperture helpers will then130 * unregister the platform device automatically. Acquired apertures are131 * released automatically if the underlying device goes away.132 *133 * The function fails if the framebuffer range, or parts of it, is currently134 * owned by another driver. To evict current owners, callers should use135 * drm_aperture_remove_conflicting_framebuffers() et al. before calling this136 * function. The function also fails if the given device is not a platform137 * device.138 *139 * Returns:140 * 0 on success, or a negative errno value otherwise.141 */142int devm_aperture_acquire_from_firmware(struct drm_device *dev, resource_size_t base,143 resource_size_t size)144{145 struct platform_device *pdev;146 147 if (drm_WARN_ON(dev, !dev_is_platform(dev->dev)))148 return -EINVAL;149 150 pdev = to_platform_device(dev->dev);151 152 return devm_aperture_acquire_for_platform_device(pdev, base, size);153}154EXPORT_SYMBOL(devm_aperture_acquire_from_firmware);155 156/**157 * drm_aperture_remove_conflicting_framebuffers - remove existing framebuffers in the given range158 * @base: the aperture's base address in physical memory159 * @size: aperture size in bytes160 * @req_driver: requesting DRM driver161 *162 * This function removes graphics device drivers which use the memory range described by163 * @base and @size.164 *165 * Returns:166 * 0 on success, or a negative errno code otherwise167 */168int drm_aperture_remove_conflicting_framebuffers(resource_size_t base, resource_size_t size,169 const struct drm_driver *req_driver)170{171 return aperture_remove_conflicting_devices(base, size, req_driver->name);172}173EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);174 175/**176 * drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices177 * @pdev: PCI device178 * @req_driver: requesting DRM driver179 *180 * This function removes graphics device drivers using the memory range configured181 * for any of @pdev's memory bars. The function assumes that a PCI device with182 * shadowed ROM drives a primary display and so kicks out vga16fb.183 *184 * Returns:185 * 0 on success, or a negative errno code otherwise186 */187int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,188 const struct drm_driver *req_driver)189{190 return aperture_remove_conflicting_pci_devices(pdev, req_driver->name);191}192EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);193