video/aperture: Provide a VGA helper for gma500 and internal use

The hardware for gma500 is different from the rest, as it uses stolen
framebuffer memory that is not available via PCI BAR. The regular PCI
removal helper cannot detect the framebuffer, while the non-PCI helper
misses possible conflicting VGA devices (i.e., a framebuffer or text
console).

Gma500 therefore calls both helpers to catch all cases. It's confusing
as it implies that there's something about the PCI device that requires
ownership management. The relationship between the PCI device and the
VGA devices is non-obvious. At worst, readers might assume that calling
two functions for clearing aperture ownership is a bug in the driver.

Hence, move the PCI removal helper's code for VGA functionality into
a separate function and call this function from gma500. Documents the
purpose of each call to aperture helpers. The change contains comments
and example code form the discussion at [1].

v5:
	* fix grammar in gma500 comment (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20230404201842.567344-1-daniel.vetter@ffwll.ch/ # 1
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406132109.32050-10-tzimmermann@suse.de

1 files changed, 34 insertions, 14 deletions

diff --git a/drivers/gpu/drm/gma500/psb_drv.c b/drivers/gpu/drm/gma500/psb_drv.c
index 4bb06a89e48d..8b64f61ffaf9 100644
--- a/drivers/gpu/drm/gma500/psb_drv.c
+++ b/drivers/gpu/drm/gma500/psb_drv.c
@@ -7,6 +7,7 @@
  *
  **************************************************************************/
 
+#include <linux/aperture.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
@@ -19,7 +20,6 @@
 #include <acpi/video.h>
 
 #include <drm/drm.h>
-#include <drm/drm_aperture.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
 #include <drm/drm_ioctl.h>
@@ -414,25 +414,45 @@ out_err:
 	return ret;
 }
 
-static int psb_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
+/*
+ * Hardware for gma500 is a hybrid device, which both acts as a PCI
+ * device (for legacy vga functionality) but also more like an
+ * integrated display on a SoC where the framebuffer simply
+ * resides in main memory and not in a special PCI bar (that
+ * internally redirects to a stolen range of main memory) like all
+ * other integrated PCI display devices implement it.
+ *
+ * To catch all cases we need to remove conflicting firmware devices
+ * for the stolen system memory and for the VGA functionality. As we
+ * currently cannot easily find the framebuffer's location in stolen
+ * memory, we remove all framebuffers here.
+ *
+ * TODO: Refactor psb_driver_load() to map vdc_reg earlier. Then
+ *       we might be able to read the framebuffer range from the
+ *       device.
+ */
+static int gma_remove_conflicting_framebuffers(struct pci_dev *pdev,
+					       const struct drm_driver *req_driver)
 {
-	struct drm_psb_private *dev_priv;
-	struct drm_device *dev;
+	resource_size_t base = 0;
+	resource_size_t size = U32_MAX; /* 4 GiB HW limit */
+	const char *name = req_driver->name;
 	int ret;
 
-	/*
-	 * We cannot yet easily find the framebuffer's location in memory. So
-	 * remove all framebuffers here. Note that we still want the pci special
-	 * handling to kick out vgacon.
-	 *
-	 * TODO: Refactor psb_driver_load() to map vdc_reg earlier. Then we
-	 *       might be able to read the framebuffer range from the device.
-	 */
-	ret = drm_aperture_remove_framebuffers(&driver);
+	ret = aperture_remove_conflicting_devices(base, size, name);
 	if (ret)
 		return ret;
 
-	ret = drm_aperture_remove_conflicting_pci_framebuffers(pdev, &driver);
+	return __aperture_remove_legacy_vga_devices(pdev);
+}
+
+static int psb_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
+{
+	struct drm_psb_private *dev_priv;
+	struct drm_device *dev;
+	int ret;
+
+	ret = gma_remove_conflicting_framebuffers(pdev, &driver);
 	if (ret)
 		return ret;