From: Ben Hutchings <ben@decadent.org.uk>
Subject: radeon, amdgpu: Firmware is required for DRM and KMS on R600 onward
Date: Tue, 08 Jan 2013 03:25:52 +0000
Bug-Debian: https://bugs.debian.org/607194
Bug-Debian: https://bugs.debian.org/607471
Bug-Debian: https://bugs.debian.org/610851
Bug-Debian: https://bugs.debian.org/627497
Bug-Debian: https://bugs.debian.org/632212
Bug-Debian: https://bugs.debian.org/637943
Bug-Debian: https://bugs.debian.org/649448
Bug-Debian: https://bugs.debian.org/697229
Bug-Debian: https://bugs.debian.org/1053764
Forwarded: no
Last-Update: 2023-11-08

radeon requires firmware/microcode for the GPU in all chips, but for
newer chips (apparently R600 'Evergreen' onward) it also expects
firmware for the memory controller and other sub-blocks.

radeon attempts to gracefully fall back and disable some features if
the firmware is not available, but becomes unstable - the framebuffer
and/or system memory may be corrupted, or the display may stay black.

Therefore, perform a basic check for the existence of
/lib/firmware/radeon when a device is probed, and abort if it
is missing, except for the pre-R600 case.

Update 2023-11-08:
In bug 1053764 Mario Limonciello <mario.limonciello@amd.com> states
that the patch isn't needed anymore for amdgpu, so remove that part
of the patch
---
 drivers/gpu/drm/radeon/radeon_drv.c     | 30 +++++++++++++++++++++++++
 1 files changed, 30 insertions(+)

--- a/drivers/gpu/drm/radeon/radeon_drv.c
+++ b/drivers/gpu/drm/radeon/radeon_drv.c
@@ -32,6 +32,8 @@
 
 #include <linux/compat.h>
 #include <linux/module.h>
+#include <linux/namei.h>
+#include <linux/path.h>
 #include <linux/pm_runtime.h>
 #include <linux/vga_switcheroo.h>
 #include <linux/mmu_notifier.h>
@@ -255,6 +257,28 @@ MODULE_DEVICE_TABLE(pci, pciidlist);
 
 static const struct drm_driver kms_driver;
 
+/* Test that /lib/firmware/radeon is a directory (or symlink to a
+ * directory).  We could try to match the udev search path, but let's
+ * keep it simple.
+ */
+static bool radeon_firmware_installed(void)
+{
+#if IS_BUILTIN(CONFIG_DRM_RADEON)
+	/* It may be too early to tell.  Assume it's there. */
+	return true;
+#else
+	struct path path;
+
+	if (kern_path("/lib/firmware/radeon", LOOKUP_DIRECTORY | LOOKUP_FOLLOW,
+		      &path) == 0) {
+		path_put(&path);
+		return true;
+	}
+
+	return false;
+#endif
+}
+
 static int radeon_pci_probe(struct pci_dev *pdev,
 			    const struct pci_device_id *ent)
 {
@@ -296,6 +320,12 @@ static int radeon_pci_probe(struct pci_d
 	if (vga_switcheroo_client_probe_defer(pdev))
 		return -EPROBE_DEFER;
 
+	if ((ent->driver_data & RADEON_FAMILY_MASK) >= CHIP_R600 &&
+	    !radeon_firmware_installed()) {
+		DRM_ERROR("radeon kernel modesetting for R600 or later requires firmware installed\n");
+		return -ENODEV;
+	}
+
 	/* Get rid of things like offb */
 	ret = drm_aperture_remove_conflicting_pci_framebuffers(pdev, &kms_driver);
 	if (ret)