1 // SPDX-License-Identifier: MIT 2 3 #include <linux/aperture.h> 4 #include <linux/device.h> 5 #include <linux/list.h> 6 #include <linux/mutex.h> 7 #include <linux/pci.h> 8 #include <linux/platform_device.h> 9 #include <linux/slab.h> 10 #include <linux/sysfb.h> 11 #include <linux/types.h> 12 #include <linux/vgaarb.h> 13 14 #include <video/vga.h> 15 16 /** 17 * DOC: overview 18 * 19 * A graphics device might be supported by different drivers, but only one 20 * driver can be active at any given time. Many systems load a generic 21 * graphics drivers, such as EFI-GOP or VESA, early during the boot process. 22 * During later boot stages, they replace the generic driver with a dedicated, 23 * hardware-specific driver. To take over the device the dedicated driver 24 * first has to remove the generic driver. Aperture functions manage 25 * ownership of framebuffer memory and hand-over between drivers. 26 * 27 * Graphics drivers should call aperture_remove_conflicting_devices() 28 * at the top of their probe function. The function removes any generic 29 * driver that is currently associated with the given framebuffer memory. 30 * An example for a graphics device on the platform bus is shown below. 31 * 32 * .. code-block:: c 33 * 34 * static int example_probe(struct platform_device *pdev) 35 * { 36 * struct resource *mem; 37 * resource_size_t base, size; 38 * int ret; 39 * 40 * mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 41 * if (!mem) 42 * return -ENODEV; 43 * base = mem->start; 44 * size = resource_size(mem); 45 * 46 * ret = aperture_remove_conflicting_devices(base, size, false, "example"); 47 * if (ret) 48 * return ret; 49 * 50 * // Initialize the hardware 51 * ... 52 * 53 * return 0; 54 * } 55 * 56 * static const struct platform_driver example_driver = { 57 * .probe = example_probe, 58 * ... 59 * }; 60 * 61 * The given example reads the platform device's I/O-memory range from the 62 * device instance. An active framebuffer will be located within this range. 63 * The call to aperture_remove_conflicting_devices() releases drivers that 64 * have previously claimed ownership of the range and are currently driving 65 * output on the framebuffer. If successful, the new driver can take over 66 * the device. 67 * 68 * While the given example uses a platform device, the aperture helpers work 69 * with every bus that has an addressable framebuffer. In the case of PCI, 70 * device drivers can also call aperture_remove_conflicting_pci_devices() and 71 * let the function detect the apertures automatically. Device drivers without 72 * knowledge of the framebuffer's location can call 73 * aperture_remove_all_conflicting_devices(), which removes all known devices. 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 * framebuffer apertures. Ownership of the framebuffer memory is achieved 78 * by calling devm_aperture_acquire_for_platform_device(). If successful, the 79 * driveris the owner of the framebuffer range. The function fails if the 80 * framebuffer is already owned by another driver. See below for an example. 81 * 82 * .. code-block:: c 83 * 84 * static int generic_probe(struct platform_device *pdev) 85 * { 86 * struct resource *mem; 87 * resource_size_t base, size; 88 * 89 * mem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 90 * if (!mem) 91 * return -ENODEV; 92 * base = mem->start; 93 * size = resource_size(mem); 94 * 95 * ret = devm_aperture_acquire_for_platform_device(pdev, base, size); 96 * if (ret) 97 * return ret; 98 * 99 * // Initialize the hardware 100 * ... 101 * 102 * return 0; 103 * } 104 * 105 * static int generic_remove(struct platform_device *) 106 * { 107 * // Hot-unplug the device 108 * ... 109 * 110 * return 0; 111 * } 112 * 113 * static const struct platform_driver generic_driver = { 114 * .probe = generic_probe, 115 * .remove = generic_remove, 116 * ... 117 * }; 118 * 119 * The similar to the previous example, the generic driver claims ownership 120 * of the framebuffer memory from its probe function. This will fail if the 121 * memory range, or parts of it, is already owned by another driver. 122 * 123 * If successful, the generic driver is now subject to forced removal by 124 * another driver. This only works for platform drivers that support hot 125 * unplugging. When a driver calls aperture_remove_conflicting_devices() 126 * et al for the registered framebuffer range, the aperture helpers call 127 * platform_device_unregister() and the generic driver unloads itself. The 128 * generic driver also has to provide a remove function to make this work. 129 * Once hot unplugged fro mhardware, it may not access the device's 130 * registers, framebuffer memory, ROM, etc afterwards. 131 */ 132 133 struct aperture_range { 134 struct device *dev; 135 resource_size_t base; 136 resource_size_t size; 137 struct list_head lh; 138 void (*detach)(struct device *dev); 139 }; 140 141 static LIST_HEAD(apertures); 142 static DEFINE_MUTEX(apertures_lock); 143 144 static bool overlap(resource_size_t base1, resource_size_t end1, 145 resource_size_t base2, resource_size_t end2) 146 { 147 return (base1 < end2) && (end1 > base2); 148 } 149 150 static void devm_aperture_acquire_release(void *data) 151 { 152 struct aperture_range *ap = data; 153 bool detached = !ap->dev; 154 155 if (detached) 156 return; 157 158 mutex_lock(&apertures_lock); 159 list_del(&ap->lh); 160 mutex_unlock(&apertures_lock); 161 } 162 163 static int devm_aperture_acquire(struct device *dev, 164 resource_size_t base, resource_size_t size, 165 void (*detach)(struct device *)) 166 { 167 size_t end = base + size; 168 struct list_head *pos; 169 struct aperture_range *ap; 170 171 mutex_lock(&apertures_lock); 172 173 list_for_each(pos, &apertures) { 174 ap = container_of(pos, struct aperture_range, lh); 175 if (overlap(base, end, ap->base, ap->base + ap->size)) { 176 mutex_unlock(&apertures_lock); 177 return -EBUSY; 178 } 179 } 180 181 ap = devm_kzalloc(dev, sizeof(*ap), GFP_KERNEL); 182 if (!ap) { 183 mutex_unlock(&apertures_lock); 184 return -ENOMEM; 185 } 186 187 ap->dev = dev; 188 ap->base = base; 189 ap->size = size; 190 ap->detach = detach; 191 INIT_LIST_HEAD(&ap->lh); 192 193 list_add(&ap->lh, &apertures); 194 195 mutex_unlock(&apertures_lock); 196 197 return devm_add_action_or_reset(dev, devm_aperture_acquire_release, ap); 198 } 199 200 static void aperture_detach_platform_device(struct device *dev) 201 { 202 struct platform_device *pdev = to_platform_device(dev); 203 204 /* 205 * Remove the device from the device hierarchy. This is the right thing 206 * to do for firmware-based DRM drivers, such as EFI, VESA or VGA. After 207 * the new driver takes over the hardware, the firmware device's state 208 * will be lost. 209 * 210 * For non-platform devices, a new callback would be required. 211 * 212 * If the aperture helpers ever need to handle native drivers, this call 213 * would only have to unplug the DRM device, so that the hardware device 214 * stays around after detachment. 215 */ 216 platform_device_unregister(pdev); 217 } 218 219 /** 220 * devm_aperture_acquire_for_platform_device - Acquires ownership of an aperture 221 * on behalf of a platform device. 222 * @pdev: the platform device to own the aperture 223 * @base: the aperture's byte offset in physical memory 224 * @size: the aperture size in bytes 225 * 226 * Installs the given device as the new owner of the aperture. The function 227 * expects the aperture to be provided by a platform device. If another 228 * driver takes over ownership of the aperture, aperture helpers will then 229 * unregister the platform device automatically. All acquired apertures are 230 * released automatically when the underlying device goes away. 231 * 232 * The function fails if the aperture, or parts of it, is currently 233 * owned by another device. To evict current owners, callers should use 234 * remove_conflicting_devices() et al. before calling this function. 235 * 236 * Returns: 237 * 0 on success, or a negative errno value otherwise. 238 */ 239 int devm_aperture_acquire_for_platform_device(struct platform_device *pdev, 240 resource_size_t base, 241 resource_size_t size) 242 { 243 return devm_aperture_acquire(&pdev->dev, base, size, aperture_detach_platform_device); 244 } 245 EXPORT_SYMBOL(devm_aperture_acquire_for_platform_device); 246 247 static void aperture_detach_devices(resource_size_t base, resource_size_t size) 248 { 249 resource_size_t end = base + size; 250 struct list_head *pos, *n; 251 252 mutex_lock(&apertures_lock); 253 254 list_for_each_safe(pos, n, &apertures) { 255 struct aperture_range *ap = container_of(pos, struct aperture_range, lh); 256 struct device *dev = ap->dev; 257 258 if (WARN_ON_ONCE(!dev)) 259 continue; 260 261 if (!overlap(base, end, ap->base, ap->base + ap->size)) 262 continue; 263 264 ap->dev = NULL; /* detach from device */ 265 list_del(&ap->lh); 266 267 ap->detach(dev); 268 } 269 270 mutex_unlock(&apertures_lock); 271 } 272 273 /** 274 * aperture_remove_conflicting_devices - remove devices in the given range 275 * @base: the aperture's base address in physical memory 276 * @size: aperture size in bytes 277 * @primary: also kick vga16fb if present; only relevant for VGA devices 278 * @name: a descriptive name of the requesting driver 279 * 280 * This function removes devices that own apertures within @base and @size. 281 * 282 * Returns: 283 * 0 on success, or a negative errno code otherwise 284 */ 285 int aperture_remove_conflicting_devices(resource_size_t base, resource_size_t size, 286 bool primary, const char *name) 287 { 288 /* 289 * If a driver asked to unregister a platform device registered by 290 * sysfb, then can be assumed that this is a driver for a display 291 * that is set up by the system firmware and has a generic driver. 292 * 293 * Drivers for devices that don't have a generic driver will never 294 * ask for this, so let's assume that a real driver for the display 295 * was already probed and prevent sysfb to register devices later. 296 */ 297 sysfb_disable(); 298 299 aperture_detach_devices(base, size); 300 301 /* 302 * If this is the primary adapter, there could be a VGA device 303 * that consumes the VGA framebuffer I/O range. Remove this device 304 * as well. 305 */ 306 if (primary) 307 aperture_detach_devices(VGA_FB_PHYS_BASE, VGA_FB_PHYS_SIZE); 308 309 return 0; 310 } 311 EXPORT_SYMBOL(aperture_remove_conflicting_devices); 312 313 /** 314 * aperture_remove_conflicting_pci_devices - remove existing framebuffers for PCI devices 315 * @pdev: PCI device 316 * @name: a descriptive name of the requesting driver 317 * 318 * This function removes devices that own apertures within any of @pdev's 319 * memory bars. The function assumes that PCI device with shadowed ROM 320 * drives a primary display and therefore kicks out vga16fb as well. 321 * 322 * Returns: 323 * 0 on success, or a negative errno code otherwise 324 */ 325 int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *name) 326 { 327 bool primary = false; 328 resource_size_t base, size; 329 int bar, ret; 330 331 #ifdef CONFIG_X86 332 primary = pdev->resource[PCI_ROM_RESOURCE].flags & IORESOURCE_ROM_SHADOW; 333 #endif 334 335 for (bar = 0; bar < PCI_STD_NUM_BARS; ++bar) { 336 if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM)) 337 continue; 338 339 base = pci_resource_start(pdev, bar); 340 size = pci_resource_len(pdev, bar); 341 ret = aperture_remove_conflicting_devices(base, size, primary, name); 342 if (ret) 343 return ret; 344 } 345 346 /* 347 * WARNING: Apparently we must kick fbdev drivers before vgacon, 348 * otherwise the vga fbdev driver falls over. 349 */ 350 ret = vga_remove_vgacon(pdev); 351 if (ret) 352 return ret; 353 354 return 0; 355 356 } 357 EXPORT_SYMBOL(aperture_remove_conflicting_pci_devices); 358