summaryrefslogtreecommitdiff
path: root/drivers/gpu/drm/drm_aperture.c
blob: 5729f3bb43989f054d70697a27c2c8036e9fb76e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
// SPDX-License-Identifier: MIT

#include <linux/aperture.h>
#include <linux/platform_device.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 const struct drm_driver example_driver = {
 *		...
 *	};
 *
 *	static int remove_conflicting_framebuffers(struct pci_dev *pdev)
 *	{
 *		resource_size_t base, size;
 *		int ret;
 *
 *		base = pci_resource_start(pdev, 0);
 *		size = pci_resource_len(pdev, 0);
 *
 *		return drm_aperture_remove_conflicting_framebuffers(base, size,
 *		                                                    &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 achieved
 * 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 owned 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.
 */

/**
 * 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)
{
	struct platform_device *pdev;

	if (drm_WARN_ON(dev, !dev_is_platform(dev->dev)))
		return -EINVAL;

	pdev = to_platform_device(dev->dev);

	return devm_aperture_acquire_for_platform_device(pdev, base, size);
}
EXPORT_SYMBOL(devm_aperture_acquire_from_firmware);

/**
 * 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
 * @req_driver: requesting DRM driver
 *
 * This function removes graphics device drivers which use the 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,
						 const struct drm_driver *req_driver)
{
	return aperture_remove_conflicting_devices(base, size, req_driver->name);
}
EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);

/**
 * drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices
 * @pdev: PCI device
 * @req_driver: requesting DRM driver
 *
 * This function removes graphics device drivers using the memory range configured
 * for any of @pdev's memory bars. The function assumes that a 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 struct drm_driver *req_driver)
{
	return aperture_remove_conflicting_pci_devices(pdev, req_driver->name);
}
EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);