From: Ben Hutchings <ben@decadent.org.uk>
Subject: radeon: 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
Forwarded: no

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.

---
--- a/drivers/gpu/drm/radeon/radeon_drv.c
+++ b/drivers/gpu/drm/radeon/radeon_drv.c
@@ -43,6 +43,8 @@
 #include <drm/drm_fb_helper.h>
 
 #include <drm/drm_crtc_helper.h>
+#include <linux/namei.h>
+#include <linux/path.h>
 
 /*
  * KMS wrapper.
@@ -311,6 +313,29 @@ static struct drm_driver kms_driver;
 
 bool radeon_device_is_virtual(void);
 
+/* 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
+ * assume people take the easy route and install
+ * firmware-linux-nonfree.
+ */
+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_kick_out_firmware_fb(struct pci_dev *pdev)
 {
 	struct apertures_struct *ap;
@@ -340,6 +365,12 @@ 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-amd-graphics.\n");
+		return -ENODEV;
+	}
+
 	/* Get rid of things like offb */
 	ret = radeon_kick_out_firmware_fb(pdev);
 	if (ret)