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 : * bool primary = false;
36 : * resource_size_t base, size;
37 : * int ret;
38 : *
39 : * base = pci_resource_start(pdev, 0);
40 : * size = pci_resource_len(pdev, 0);
41 : * #ifdef CONFIG_X86
42 : * primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
43 : * #endif
44 : *
45 : * return drm_aperture_remove_conflicting_framebuffers(base, size, primary,
46 : * &example_driver);
47 : * }
48 : *
49 : * static int probe(struct pci_dev *pdev)
50 : * {
51 : * int ret;
52 : *
53 : * // Remove any generic drivers...
54 : * ret = remove_conflicting_framebuffers(pdev);
55 : * if (ret)
56 : * return ret;
57 : *
58 : * // ... and initialize the hardware.
59 : * ...
60 : *
61 : * drm_dev_register();
62 : *
63 : * return 0;
64 : * }
65 : *
66 : * PCI device drivers should call
67 : * drm_aperture_remove_conflicting_pci_framebuffers() and let it detect the
68 : * framebuffer apertures automatically. Device drivers without knowledge of
69 : * the framebuffer's location shall call drm_aperture_remove_framebuffers(),
70 : * which removes all drivers for known framebuffer.
71 : *
72 : * Drivers that are susceptible to being removed by other drivers, such as
73 : * generic EFI or VESA drivers, have to register themselves as owners of their
74 : * given framebuffer memory. Ownership of the framebuffer memory is achieved
75 : * by calling devm_aperture_acquire_from_firmware(). On success, the driver
76 : * is the owner of the framebuffer range. The function fails if the
77 : * framebuffer is already owned by another driver. See below for an example.
78 : *
79 : * .. code-block:: c
80 : *
81 : * static int acquire_framebuffers(struct drm_device *dev, struct platform_device *pdev)
82 : * {
83 : * resource_size_t base, size;
84 : *
85 : * mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
86 : * if (!mem)
87 : * return -EINVAL;
88 : * base = mem->start;
89 : * size = resource_size(mem);
90 : *
91 : * return devm_acquire_aperture_from_firmware(dev, base, size);
92 : * }
93 : *
94 : * static int probe(struct platform_device *pdev)
95 : * {
96 : * struct drm_device *dev;
97 : * int ret;
98 : *
99 : * // ... Initialize the device...
100 : * dev = devm_drm_dev_alloc();
101 : * ...
102 : *
103 : * // ... and acquire ownership of the framebuffer.
104 : * ret = acquire_framebuffers(dev, pdev);
105 : * if (ret)
106 : * return ret;
107 : *
108 : * drm_dev_register(dev, 0);
109 : *
110 : * return 0;
111 : * }
112 : *
113 : * The generic driver is now subject to forced removal by other drivers. This
114 : * only works for platform drivers that support hot unplug.
115 : * When a driver calls drm_aperture_remove_conflicting_framebuffers() et al.
116 : * for the registered framebuffer range, the aperture helpers call
117 : * platform_device_unregister() and the generic driver unloads itself. It
118 : * may not access the device's registers, framebuffer memory, ROM, etc
119 : * afterwards.
120 : */
121 :
122 : /**
123 : * devm_aperture_acquire_from_firmware - Acquires ownership of a firmware framebuffer
124 : * on behalf of a DRM driver.
125 : * @dev: the DRM device to own the framebuffer memory
126 : * @base: the framebuffer's byte offset in physical memory
127 : * @size: the framebuffer size in bytes
128 : *
129 : * Installs the given device as the new owner of the framebuffer. The function
130 : * expects the framebuffer to be provided by a platform device that has been
131 : * set up by firmware. Firmware can be any generic interface, such as EFI,
132 : * VESA, VGA, etc. If the native hardware driver takes over ownership of the
133 : * framebuffer range, the firmware state gets lost. Aperture helpers will then
134 : * unregister the platform device automatically. Acquired apertures are
135 : * released automatically if the underlying device goes away.
136 : *
137 : * The function fails if the framebuffer range, or parts of it, is currently
138 : * owned by another driver. To evict current owners, callers should use
139 : * drm_aperture_remove_conflicting_framebuffers() et al. before calling this
140 : * function. The function also fails if the given device is not a platform
141 : * device.
142 : *
143 : * Returns:
144 : * 0 on success, or a negative errno value otherwise.
145 : */
146 0 : int devm_aperture_acquire_from_firmware(struct drm_device *dev, resource_size_t base,
147 : resource_size_t size)
148 : {
149 : struct platform_device *pdev;
150 :
151 0 : if (drm_WARN_ON(dev, !dev_is_platform(dev->dev)))
152 : return -EINVAL;
153 :
154 0 : pdev = to_platform_device(dev->dev);
155 :
156 0 : return devm_aperture_acquire_for_platform_device(pdev, base, size);
157 : }
158 : EXPORT_SYMBOL(devm_aperture_acquire_from_firmware);
159 :
160 : /**
161 : * drm_aperture_remove_conflicting_framebuffers - remove existing framebuffers in the given range
162 : * @base: the aperture's base address in physical memory
163 : * @size: aperture size in bytes
164 : * @primary: also kick vga16fb if present
165 : * @req_driver: requesting DRM driver
166 : *
167 : * This function removes graphics device drivers which use the memory range described by
168 : * @base and @size.
169 : *
170 : * Returns:
171 : * 0 on success, or a negative errno code otherwise
172 : */
173 0 : int drm_aperture_remove_conflicting_framebuffers(resource_size_t base, resource_size_t size,
174 : bool primary, const struct drm_driver *req_driver)
175 : {
176 0 : return aperture_remove_conflicting_devices(base, size, primary, req_driver->name);
177 : }
178 : EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);
179 :
180 : /**
181 : * drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices
182 : * @pdev: PCI device
183 : * @req_driver: requesting DRM driver
184 : *
185 : * This function removes graphics device drivers using the memory range configured
186 : * for any of @pdev's memory bars. The function assumes that a PCI device with
187 : * shadowed ROM drives a primary display and so kicks out vga16fb.
188 : *
189 : * Returns:
190 : * 0 on success, or a negative errno code otherwise
191 : */
192 0 : int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
193 : const struct drm_driver *req_driver)
194 : {
195 0 : return aperture_remove_conflicting_pci_devices(pdev, req_driver->name);
196 : }
197 : EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);
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