Line data Source code
1 : // SPDX-License-Identifier: MIT
2 :
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: overview
12 : *
13 : * A graphics device might be supported by different drivers, but only one
14 : * driver can be active at any given time. Many systems load a generic
15 : * 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 driver
18 : * first has to remove the generic driver. DRM aperture functions manage
19 : * 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 generic
23 : * 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 the
25 : * example given below.
26 : *
27 : * .. code-block:: c
28 : *
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 call
63 : * drm_aperture_remove_conflicting_pci_framebuffers() and let it detect the
64 : * framebuffer apertures automatically. Device drivers without knowledge of
65 : * 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 as
69 : * generic EFI or VESA drivers, have to register themselves as owners of their
70 : * given framebuffer memory. Ownership of the framebuffer memory is achieved
71 : * by calling devm_aperture_acquire_from_firmware(). On success, the driver
72 : * is the owner of the framebuffer range. The function fails if the
73 : * framebuffer is already owned by another driver. See below for an example.
74 : *
75 : * .. code-block:: c
76 : *
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. This
110 : * 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 call
113 : * platform_device_unregister() and the generic driver unloads itself. It
114 : * may not access the device's registers, framebuffer memory, ROM, etc
115 : * afterwards.
116 : */
117 :
118 : /**
119 : * devm_aperture_acquire_from_firmware - Acquires ownership of a firmware framebuffer
120 : * on behalf of a DRM driver.
121 : * @dev: the DRM device to own the framebuffer memory
122 : * @base: the framebuffer's byte offset in physical memory
123 : * @size: the framebuffer size in bytes
124 : *
125 : * Installs the given device as the new owner of the framebuffer. The function
126 : * expects the framebuffer to be provided by a platform device that has been
127 : * 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 the
129 : * framebuffer range, the firmware state gets lost. Aperture helpers will then
130 : * unregister the platform device automatically. Acquired apertures are
131 : * released automatically if the underlying device goes away.
132 : *
133 : * The function fails if the framebuffer range, or parts of it, is currently
134 : * owned by another driver. To evict current owners, callers should use
135 : * drm_aperture_remove_conflicting_framebuffers() et al. before calling this
136 : * function. The function also fails if the given device is not a platform
137 : * device.
138 : *
139 : * Returns:
140 : * 0 on success, or a negative errno value otherwise.
141 : */
142 0 : int 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 0 : if (drm_WARN_ON(dev, !dev_is_platform(dev->dev)))
148 : return -EINVAL;
149 :
150 0 : pdev = to_platform_device(dev->dev);
151 :
152 0 : return devm_aperture_acquire_for_platform_device(pdev, base, size);
153 : }
154 : EXPORT_SYMBOL(devm_aperture_acquire_from_firmware);
155 :
156 : /**
157 : * drm_aperture_remove_conflicting_framebuffers - remove existing framebuffers in the given range
158 : * @base: the aperture's base address in physical memory
159 : * @size: aperture size in bytes
160 : * @req_driver: requesting DRM driver
161 : *
162 : * This function removes graphics device drivers which use the memory range described by
163 : * @base and @size.
164 : *
165 : * Returns:
166 : * 0 on success, or a negative errno code otherwise
167 : */
168 0 : int drm_aperture_remove_conflicting_framebuffers(resource_size_t base, resource_size_t size,
169 : const struct drm_driver *req_driver)
170 : {
171 0 : return aperture_remove_conflicting_devices(base, size, req_driver->name);
172 : }
173 : EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);
174 :
175 : /**
176 : * drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices
177 : * @pdev: PCI device
178 : * @req_driver: requesting DRM driver
179 : *
180 : * This function removes graphics device drivers using the memory range configured
181 : * for any of @pdev's memory bars. The function assumes that a PCI device with
182 : * shadowed ROM drives a primary display and so kicks out vga16fb.
183 : *
184 : * Returns:
185 : * 0 on success, or a negative errno code otherwise
186 : */
187 0 : int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
188 : const struct drm_driver *req_driver)
189 : {
190 0 : return aperture_remove_conflicting_pci_devices(pdev, req_driver->name);
191 : }
192 : EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);
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