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 const struct drm_driver example_driver = { 37 * ... 38 * }; 39 * 40 * static int remove_conflicting_framebuffers(struct pci_dev *pdev) 41 * { 42 * bool primary = false; 43 * resource_size_t base, size; 44 * int ret; 45 * 46 * base = pci_resource_start(pdev, 0); 47 * size = pci_resource_len(pdev, 0); 48 * #ifdef CONFIG_X86 49 * primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW; 50 * #endif 51 * 52 * return drm_aperture_remove_conflicting_framebuffers(base, size, primary, 53 * &example_driver); 54 * } 55 * 56 * static int probe(struct pci_dev *pdev) 57 * { 58 * int ret; 59 * 60 * // Remove any generic drivers... 61 * ret = remove_conflicting_framebuffers(pdev); 62 * if (ret) 63 * return ret; 64 * 65 * // ... and initialize the hardware. 66 * ... 67 * 68 * drm_dev_register(); 69 * 70 * return 0; 71 * } 72 * 73 * PCI device drivers should call 74 * drm_aperture_remove_conflicting_pci_framebuffers() and let it detect the 75 * framebuffer apertures automatically. Device drivers without knowledge of 76 * the framebuffer's location shall call drm_aperture_remove_framebuffers(), 77 * which removes all drivers for known framebuffer. 78 * 79 * Drivers that are susceptible to being removed by other drivers, such as 80 * generic EFI or VESA drivers, have to register themselves as owners of their 81 * given framebuffer memory. Ownership of the framebuffer memory is achieved 82 * by calling devm_aperture_acquire_from_firmware(). On success, the driver 83 * is the owner of the framebuffer range. The function fails if the 84 * framebuffer is already by another driver. See below for an example. 85 * 86 * .. code-block:: c 87 * 88 * static int acquire_framebuffers(struct drm_device *dev, struct platform_device *pdev) 89 * { 90 * resource_size_t base, size; 91 * 92 * mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 93 * if (!mem) 94 * return -EINVAL; 95 * base = mem->start; 96 * size = resource_size(mem); 97 * 98 * return devm_acquire_aperture_from_firmware(dev, base, size); 99 * } 100 * 101 * static int probe(struct platform_device *pdev) 102 * { 103 * struct drm_device *dev; 104 * int ret; 105 * 106 * // ... Initialize the device... 107 * dev = devm_drm_dev_alloc(); 108 * ... 109 * 110 * // ... and acquire ownership of the framebuffer. 111 * ret = acquire_framebuffers(dev, pdev); 112 * if (ret) 113 * return ret; 114 * 115 * drm_dev_register(dev, 0); 116 * 117 * return 0; 118 * } 119 * 120 * The generic driver is now subject to forced removal by other drivers. This 121 * only works for platform drivers that support hot unplug. 122 * When a driver calls drm_aperture_remove_conflicting_framebuffers() et al 123 * for the registered framebuffer range, the aperture helpers call 124 * platform_device_unregister() and the generic driver unloads itself. It 125 * may not access the device's registers, framebuffer memory, ROM, etc 126 * afterwards. 127 */ 128 129 struct drm_aperture { 130 struct drm_device *dev; 131 resource_size_t base; 132 resource_size_t size; 133 struct list_head lh; 134 void (*detach)(struct drm_device *dev); 135 }; 136 137 static LIST_HEAD(drm_apertures); 138 static DEFINE_MUTEX(drm_apertures_lock); 139 140 static bool overlap(resource_size_t base1, resource_size_t end1, 141 resource_size_t base2, resource_size_t end2) 142 { 143 return (base1 < end2) && (end1 > base2); 144 } 145 146 static void devm_aperture_acquire_release(void *data) 147 { 148 struct drm_aperture *ap = data; 149 bool detached = !ap->dev; 150 151 if (detached) 152 return; 153 154 mutex_lock(&drm_apertures_lock); 155 list_del(&ap->lh); 156 mutex_unlock(&drm_apertures_lock); 157 } 158 159 static int devm_aperture_acquire(struct drm_device *dev, 160 resource_size_t base, resource_size_t size, 161 void (*detach)(struct drm_device *)) 162 { 163 size_t end = base + size; 164 struct list_head *pos; 165 struct drm_aperture *ap; 166 167 mutex_lock(&drm_apertures_lock); 168 169 list_for_each(pos, &drm_apertures) { 170 ap = container_of(pos, struct drm_aperture, lh); 171 if (overlap(base, end, ap->base, ap->base + ap->size)) { 172 mutex_unlock(&drm_apertures_lock); 173 return -EBUSY; 174 } 175 } 176 177 ap = devm_kzalloc(dev->dev, sizeof(*ap), GFP_KERNEL); 178 if (!ap) { 179 mutex_unlock(&drm_apertures_lock); 180 return -ENOMEM; 181 } 182 183 ap->dev = dev; 184 ap->base = base; 185 ap->size = size; 186 ap->detach = detach; 187 INIT_LIST_HEAD(&ap->lh); 188 189 list_add(&ap->lh, &drm_apertures); 190 191 mutex_unlock(&drm_apertures_lock); 192 193 return devm_add_action_or_reset(dev->dev, devm_aperture_acquire_release, ap); 194 } 195 196 static void drm_aperture_detach_firmware(struct drm_device *dev) 197 { 198 struct platform_device *pdev = to_platform_device(dev->dev); 199 200 /* 201 * Remove the device from the device hierarchy. This is the right thing 202 * to do for firmware-based DRM drivers, such as EFI, VESA or VGA. After 203 * the new driver takes over the hardware, the firmware device's state 204 * will be lost. 205 * 206 * For non-platform devices, a new callback would be required. 207 * 208 * If the aperture helpers ever need to handle native drivers, this call 209 * would only have to unplug the DRM device, so that the hardware device 210 * stays around after detachment. 211 */ 212 platform_device_unregister(pdev); 213 } 214 215 /** 216 * devm_aperture_acquire_from_firmware - Acquires ownership of a firmware framebuffer 217 * on behalf of a DRM driver. 218 * @dev: the DRM device to own the framebuffer memory 219 * @base: the framebuffer's byte offset in physical memory 220 * @size: the framebuffer size in bytes 221 * 222 * Installs the given device as the new owner of the framebuffer. The function 223 * expects the framebuffer to be provided by a platform device that has been 224 * set up by firmware. Firmware can be any generic interface, such as EFI, 225 * VESA, VGA, etc. If the native hardware driver takes over ownership of the 226 * framebuffer range, the firmware state gets lost. Aperture helpers will then 227 * unregister the platform device automatically. Acquired apertures are 228 * released automatically if the underlying device goes away. 229 * 230 * The function fails if the framebuffer range, or parts of it, is currently 231 * owned by another driver. To evict current owners, callers should use 232 * drm_aperture_remove_conflicting_framebuffers() et al. before calling this 233 * function. The function also fails if the given device is not a platform 234 * device. 235 * 236 * Returns: 237 * 0 on success, or a negative errno value otherwise. 238 */ 239 int devm_aperture_acquire_from_firmware(struct drm_device *dev, resource_size_t base, 240 resource_size_t size) 241 { 242 if (drm_WARN_ON(dev, !dev_is_platform(dev->dev))) 243 return -EINVAL; 244 245 return devm_aperture_acquire(dev, base, size, drm_aperture_detach_firmware); 246 } 247 EXPORT_SYMBOL(devm_aperture_acquire_from_firmware); 248 249 static void drm_aperture_detach_drivers(resource_size_t base, resource_size_t size) 250 { 251 resource_size_t end = base + size; 252 struct list_head *pos, *n; 253 254 mutex_lock(&drm_apertures_lock); 255 256 list_for_each_safe(pos, n, &drm_apertures) { 257 struct drm_aperture *ap = 258 container_of(pos, struct drm_aperture, lh); 259 struct drm_device *dev = ap->dev; 260 261 if (WARN_ON_ONCE(!dev)) 262 continue; 263 264 if (!overlap(base, end, ap->base, ap->base + ap->size)) 265 continue; 266 267 ap->dev = NULL; /* detach from device */ 268 list_del(&ap->lh); 269 270 ap->detach(dev); 271 } 272 273 mutex_unlock(&drm_apertures_lock); 274 } 275 276 /** 277 * drm_aperture_remove_conflicting_framebuffers - remove existing framebuffers in the given range 278 * @base: the aperture's base address in physical memory 279 * @size: aperture size in bytes 280 * @primary: also kick vga16fb if present 281 * @req_driver: requesting DRM driver 282 * 283 * This function removes graphics device drivers which use memory range described by 284 * @base and @size. 285 * 286 * Returns: 287 * 0 on success, or a negative errno code otherwise 288 */ 289 int drm_aperture_remove_conflicting_framebuffers(resource_size_t base, resource_size_t size, 290 bool primary, const struct drm_driver *req_driver) 291 { 292 #if IS_REACHABLE(CONFIG_FB) 293 struct apertures_struct *a; 294 int ret; 295 296 a = alloc_apertures(1); 297 if (!a) 298 return -ENOMEM; 299 300 a->ranges[0].base = base; 301 a->ranges[0].size = size; 302 303 ret = remove_conflicting_framebuffers(a, req_driver->name, primary); 304 kfree(a); 305 306 if (ret) 307 return ret; 308 #endif 309 310 drm_aperture_detach_drivers(base, size); 311 312 return 0; 313 } 314 EXPORT_SYMBOL(drm_aperture_remove_conflicting_framebuffers); 315 316 /** 317 * drm_aperture_remove_conflicting_pci_framebuffers - remove existing framebuffers for PCI devices 318 * @pdev: PCI device 319 * @req_driver: requesting DRM driver 320 * 321 * This function removes graphics device drivers using memory range configured 322 * for any of @pdev's memory bars. The function assumes that PCI device with 323 * shadowed ROM drives a primary display and so kicks out vga16fb. 324 * 325 * Returns: 326 * 0 on success, or a negative errno code otherwise 327 */ 328 int drm_aperture_remove_conflicting_pci_framebuffers(struct pci_dev *pdev, 329 const struct drm_driver *req_driver) 330 { 331 resource_size_t base, size; 332 int bar, ret = 0; 333 334 for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) { 335 if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) 336 continue; 337 base = pci_resource_start(pdev, bar); 338 size = pci_resource_len(pdev, bar); 339 drm_aperture_detach_drivers(base, size); 340 } 341 342 /* 343 * WARNING: Apparently we must kick fbdev drivers before vgacon, 344 * otherwise the vga fbdev driver falls over. 345 */ 346 #if IS_REACHABLE(CONFIG_FB) 347 ret = remove_conflicting_pci_framebuffers(pdev, req_driver->name); 348 #endif 349 if (ret == 0) 350 ret = vga_remove_vgacon(pdev); 351 return ret; 352 } 353 EXPORT_SYMBOL(drm_aperture_remove_conflicting_pci_framebuffers); 354