LCOV - code coverage report
Current view: top level - drivers/gpu/drm - drm_aperture.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 0 8 0.0 %
Date: 2023-03-27 20:00:47 Functions: 0 3 0.0 %

          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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