drm/amdgpu: disable runpm if we are the primary adapter

If we are the primary adapter (i.e., the one used by the firwmare
framebuffer), disable runtime pm. This fixes a regression caused
by commit 55285e21f045 which results in the displays waking up
shortly after they go to sleep due to the device coming out of
runtime suspend and sending a hotplug uevent.

v2: squash in reworked fix from Evan

Fixes: 55285e21f045 ("fbdev/efifb: Release PCI device's runtime PM ref during FB destroy")
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=215203
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1840
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

···
 	bool                            runpm;
 	bool                            in_runpm;
 	bool                            has_pr3;
+	bool                            is_fw_fb;
 
 	bool                            pm_sysfs_en;
 	bool                            ucode_sysfs_en;

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

···
 #include <linux/mmu_notifier.h>
 #include <linux/suspend.h>
 #include <linux/cc_platform.h>
+#include <linux/fb.h>
 
 #include "amdgpu.h"
 #include "amdgpu_irq.h"
···
 
 static const struct drm_driver amdgpu_kms_driver;
 
+static bool amdgpu_is_fw_framebuffer(resource_size_t base,
+				     resource_size_t size)
+{
+	bool found = false;
+#if IS_REACHABLE(CONFIG_FB)
+	struct apertures_struct *a;
+
+	a = alloc_apertures(1);
+	if (!a)
+		return false;
+
+	a->ranges[0].base = base;
+	a->ranges[0].size = size;
+
+	found = is_firmware_framebuffer(a);
+	kfree(a);
+#endif
+	return found;
+}
+
 static int amdgpu_pci_probe(struct pci_dev *pdev,
 			    const struct pci_device_id *ent)
 {
···
 	unsigned long flags = ent->driver_data;
 	int ret, retry = 0, i;
 	bool supports_atomic = false;
+	bool is_fw_fb;
+	resource_size_t base, size;
 
 	/* skip devices which are owned by radeon */
 	for (i = 0; i < ARRAY_SIZE(amdgpu_unsupported_pciidlist); i++) {
···
 	}
 #endif
 
+	base = pci_resource_start(pdev, 0);
+	size = pci_resource_len(pdev, 0);
+	is_fw_fb = amdgpu_is_fw_framebuffer(base, size);
+
 	/* Get rid of things like offb */
 	ret = drm_aperture_remove_conflicting_pci_framebuffers(pdev, &amdgpu_kms_driver);
 	if (ret)
···
 	adev->dev  = &pdev->dev;
 	adev->pdev = pdev;
 	ddev = adev_to_drm(adev);
+	adev->is_fw_fb = is_fw_fb;
 
 	if (!supports_atomic)
 		ddev->driver_features &= ~DRIVER_ATOMIC;

drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c

···
 			adev->runpm = true;
 			break;
 		}
+		/* XXX: disable runtime pm if we are the primary adapter
+		 * to avoid displays being re-enabled after DPMS.
+		 * This needs to be sorted out and fixed properly.
+		 */
+		if (adev->is_fw_fb)
+			adev->runpm = false;
 		if (adev->runpm)
 			dev_info(adev->dev, "Using BACO for runtime pm\n");
 	}