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1// SPDX-License-Identifier: MIT
2
3#include <linux/device.h>
4#include <linux/fb.h>
5#include <linux/list.h>
6#include <linux/mutex.h>
7#include <linux/pci.h>
8#include <linux/platform_device.h> /* for firmware helpers */
9#include <linux/slab.h>
10#include <linux/types.h>
11#include <linux/vgaarb.h>
12
13#include <drm/drm_aperture.h>
14#include <drm/drm_drv.h>
15#include <drm/drm_print.h>
16
17/**
18 * DOC: overview
19 *
20 * A graphics device might be supported by different drivers, but only one
21 * driver can be active at any given time. Many systems load a generic
22 * graphics drivers, such as EFI-GOP or VESA, early during the boot process.
23 * During later boot stages, they replace the generic driver with a dedicated,
24 * hardware-specific driver. To take over the device the dedicated driver
25 * first has to remove the generic driver. DRM aperture functions manage
26 * ownership of DRM framebuffer memory and hand-over between drivers.
27 *
28 * DRM drivers should call drm_aperture_remove_conflicting_framebuffers()
29 * at the top of their probe function. The function removes any generic
30 * driver that is currently associated with the given framebuffer memory.
31 * If the framebuffer is located at PCI BAR 0, the rsp code looks as in the
32 * example given below.
33 *
34 * .. code-block:: c
35 *
36 * static int remove_conflicting_framebuffers(struct pci_dev *pdev)
37 * {
38 * bool primary = false;
39 * resource_size_t base, size;
40 * int ret;
41 *
42 * base = pci_resource_start(pdev, 0);
43 * size = pci_resource_len(pdev, 0);
44 * #ifdef CONFIG_X86
45 * primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW;
46 * #endif
47 *
48 * return drm_aperture_remove_conflicting_framebuffers(base, size, primary,
49 * "example driver");
50 * }
51 *
52 * static int probe(struct pci_dev *pdev)
53 * {
54 * int ret;
55 *
56 * // Remove any generic drivers...
57 * ret = remove_conflicting_framebuffers(pdev);
58 * if (ret)
59 * return ret;
60 *
61 * // ... and initialize the hardware.
62 * ...
63 *
64 * drm_dev_register();
65 *
66 * return 0;
67 * }
68 *
69 * PCI device drivers should call
70 * drm_aperture_remove_conflicting_pci_framebuffers() and let it detect the
71 * framebuffer apertures automatically. Device drivers without knowledge of
72 * the framebuffer's location shall call drm_aperture_remove_framebuffers(),
73 * which removes all drivers for known framebuffer.
74 *
75 * Drivers that are susceptible to being removed by other drivers, such as
76 * generic EFI or VESA drivers, have to register themselves as owners of their
77 * given framebuffer memory. Ownership of the framebuffer memory is achived
78 * by calling devm_aperture_acquire_from_firmware(). On success, the driver
79 * is the owner of the framebuffer range. The function fails if the
80 * framebuffer is already by another driver. See below for an example.
81 *
82 * .. code-block:: c
83 *
84 * static int acquire_framebuffers(struct drm_device *dev, struct platform_device *pdev)
85 * {
86 * resource_size_t base, size;
87 *
88 * mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
89 * if (!mem)
90 * return -EINVAL;
91 * base = mem->start;
92 * size = resource_size(mem);
93 *
94 * return devm_acquire_aperture_from_firmware(dev, base, size);
95 * }
96 *
97 * static int probe(struct platform_device *pdev)
98 * {
99 * struct drm_device *dev;
100 * int ret;
101 *
102 * // ... Initialize the device...
103 * dev = devm_drm_dev_alloc();
104 * ...
105 *
106 * // ... and acquire ownership of the framebuffer.
107 * ret = acquire_framebuffers(dev, pdev);
108 * if (ret)
109 * return ret;
110 *
111 * drm_dev_register(dev, 0);
112 *
113 * return 0;
114 * }
115 *
116 * The generic driver is now subject to forced removal by other drivers. This
117 * only works for platform drivers that support hot unplug.
118 * When a driver calls drm_aperture_remove_conflicting_framebuffers() et al
119 * for the registered framebuffer range, the aperture helpers call
120 * platform_device_unregister() and the generic driver unloads itself. It
121 * may not access the device's registers, framebuffer memory, ROM, etc
122 * afterwards.
123 */
124
125struct drm_aperture {
126 struct drm_device *dev;
127 resource_size_t base;
128 resource_size_t size;
129 struct list_head lh;
130 void (*detach)(struct drm_device *dev);
131};
132
133static LIST_HEAD(drm_apertures);
134static DEFINE_MUTEX(drm_apertures_lock);
135
136static bool overlap(resource_size_t base1, resource_size_t end1,
137 resource_size_t base2, resource_size_t end2)
138{
139 return (base1 < end2) && (end1 > base2);
140}
141
142static void devm_aperture_acquire_release(void *data)
143{
144 struct drm_aperture *ap = data;
145 bool detached = !ap->dev;
146
147 if (detached)
148 return;
149
150 mutex_lock(&drm_apertures_lock);
151 list_del(&ap->lh);
152 mutex_unlock(&drm_apertures_lock);
153}
154
155static int devm_aperture_acquire(struct drm_device *dev,
156 resource_size_t base, resource_size_t size,
157 void (*detach)(struct drm_device *))
158{
159 size_t end = base + size;
160 struct list_head *pos;
161 struct drm_aperture *ap;
162
163 mutex_lock(&drm_apertures_lock);
164
165 list_for_each(pos, &drm_apertures) {
166 ap = container_of(pos, struct drm_aperture, lh);
167 if (overlap(base, end, ap->base, ap->base + ap->size)) {
168 mutex_unlock(&drm_apertures_lock);
169 return -EBUSY;
170 }
171 }
172
173 ap = devm_kzalloc(dev->dev, sizeof(*ap), GFP_KERNEL);
174 if (!ap) {
175 mutex_unlock(&drm_apertures_lock);
176 return -ENOMEM;
177 }
178
179 ap->dev = dev;
180 ap->base = base;
181 ap->size = size;
182 ap->detach = detach;
183 INIT_LIST_HEAD(&ap->lh);
184
185 list_add(&ap->lh, &drm_apertures);
186
187 mutex_unlock(&drm_apertures_lock);
188
189 return devm_add_action_or_reset(dev->dev, devm_aperture_acquire_release, ap);
190}
191
192static void drm_aperture_detach_firmware(struct drm_device *dev)
193{
194 struct platform_device *pdev = to_platform_device(dev->dev);
195
196 /*
197 * Remove the device from the device hierarchy. This is the right thing
198 * to do for firmware-based DRM drivers, such as EFI, VESA or VGA. After
199 * the new driver takes over the hardware, the firmware device's state
200 * will be lost.
201 *
202 * For non-platform devices, a new callback would be required.
203 *
204 * If the aperture helpers ever need to handle native drivers, this call
205 * would only have to unplug the DRM device, so that the hardware device
206 * stays around after detachment.
207 */
208 platform_device_unregister(pdev);
209}
210
211/**
212 * devm_aperture_acquire_from_firmware - Acquires ownership of a firmware framebuffer
213 * on behalf of a DRM driver.
214 * @dev: the DRM device to own the framebuffer memory
215 * @base: the framebuffer's byte offset in physical memory
216 * @size: the framebuffer size in bytes
217 *
218 * Installs the given device as the new owner of the framebuffer. The function
219 * expects the framebuffer to be provided by a platform device that has been
220 * set up by firmware. Firmware can be any generic interface, such as EFI,
221 * VESA, VGA, etc. If the native hardware driver takes over ownership of the
222 * framebuffer range, the firmware state gets lost. Aperture helpers will then
223 * unregister the platform device automatically. Acquired apertures are
224 * released automatically if the underlying device goes away.
225 *
226 * The function fails if the framebuffer range, or parts of it, is currently
227 * owned by another driver. To evict current owners, callers should use
228 * drm_aperture_remove_conflicting_framebuffers() et al. before calling this
229 * function. The function also fails if the given device is not a platform
230 * device.
231 *
232 * Returns:
233 * 0 on success, or a negative errno value otherwise.
234 */
235int devm_aperture_acquire_from_firmware(struct drm_device *dev, resource_size_t base,
236 resource_size_t size)
237{
238 if (drm_WARN_ON(dev, !dev_is_platform(dev->dev)))
239 return -EINVAL;
240
241 return devm_aperture_acquire(dev, base, size, drm_aperture_detach_firmware);
242}
243EXPORT_SYMBOL(devm_aperture_acquire_from_firmware);
244
245static void drm_aperture_detach_drivers(resource_size_t base, resource_size_t size)
246{
247 resource_size_t end = base + size;
248 struct list_head *pos, *n;
249
250 mutex_lock(&drm_apertures_lock);
251
252 list_for_each_safe(pos, n, &drm_apertures) {
253 struct drm_aperture *ap =
254 container_of(pos, struct drm_aperture, lh);
255 struct drm_device *dev = ap->dev;
256
257 if (WARN_ON_ONCE(!dev))
258 continue;
259
260 if (!overlap(base, end, ap->base, ap->base + ap->size))
261 continue;
262
263 ap->dev = NULL; /* detach from device */
264 list_del(&ap->lh);
265
266 ap->detach(dev);
267 }
268
269 mutex_unlock(&drm_apertures_lock);
270}
271
272/**
273 * drm_aperture_remove_conflicting_framebuffers - remove existing framebuffers in the given range
274 * @base: the aperture's base address in physical memory
275 * @size: aperture size in bytes
276 * @primary: also kick vga16fb if present
277 * @name: requesting driver name
278 *
279 * This function removes graphics device drivers which use memory range described by
280 * @base and @size.
281 *
282 * Returns:
283 * 0 on success, or a negative errno code otherwise
284 */
285int drm_aperture_remove_conflicting_framebuffers(resource_size_t base, resource_size_t size,
286 bool primary, const char *name)
287{
288#if IS_REACHABLE(CONFIG_FB)
289 struct apertures_struct *a;
290 int ret;
291
292 a = alloc_apertures(1);
293 if (!a)
294 return -ENOMEM;
295
296 a->ranges[0].base = base;
297 a->ranges[0].size = size;
298
299 ret = remove_conflicting_framebuffers(a, name, primary);
300 kfree(a);
301
302 if (ret)
303 return ret;
304#endif
305
306 drm_aperture_detach_drivers(base, size);
307
308 return 0;
309}
310EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers);
311
312/**
313 * drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices
314 * @pdev: PCI device
315 * @name: requesting driver name
316 *
317 * This function removes graphics device drivers using memory range configured
318 * for any of @pdev's memory bars. The function assumes that PCI device with
319 * shadowed ROM drives a primary display and so kicks out vga16fb.
320 *
321 * Returns:
322 * 0 on success, or a negative errno code otherwise
323 */
324int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev, const char *name)
325{
326 resource_size_t base, size;
327 int bar, ret = 0;
328
329 for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) {
330 if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
331 continue;
332 base = pci_resource_start(pdev, bar);
333 size = pci_resource_len(pdev, bar);
334 drm_aperture_detach_drivers(base, size);
335 }
336
337 /*
338 * WARNING: Apparently we must kick fbdev drivers before vgacon,
339 * otherwise the vga fbdev driver falls over.
340 */
341#if IS_REACHABLE(CONFIG_FB)
342 ret = remove_conflicting_pci_framebuffers(pdev, name);
343#endif
344 if (ret == 0)
345 ret = vga_remove_vgacon(pdev);
346 return ret;
347}
348EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers);