drm/i915/opregion: let user specify override VBT via firmware load

Sometimes it would be most enlightening to debug systems by replacing
the VBT to be used. For example, in the referenced bug the BIOS provides
different VBT depending on the boot mode (UEFI vs. legacy). It would be
interesting to try the failing boot mode with the VBT from the working
boot, and see if that makes a difference.

Add a module parameter to load the VBT using the firmware loader, not
unlike the EDID firmware mechanism.

As a starting point for experimenting, one can pick up the BIOS provided
VBT from /sys/kernel/debug/dri/0/i915_opregion/i915_vbt.

v2: clarify firmware load return value check (Bob)

v3: kfree the loaded firmware blob

References: https://bugs.freedesktop.org/show_bug.cgi?id=97822#c83
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170817115209.25912-1-jani.nikula@intel.com

4 files changed, 51 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 6c25c8520c87..3ee4fd2a9b41 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -646,6 +646,7 @@ struct intel_opregion {
         u32 swsci_sbcb_sub_functions;
         struct opregion_asle *asle;
         void *rvda;
+        void *vbt_firmware;
         const void *vbt;
         u32 vbt_size;
         u32 *lid_state;
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 14e2c2e57f96..8ab003dca113 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -118,6 +118,10 @@ MODULE_PARM_DESC(vbt_sdvo_panel_type,
 module_param_named_unsafe(reset, i915.reset, int, 0600);
 MODULE_PARM_DESC(reset, "Attempt GPU resets (0=disabled, 1=full gpu reset, 2=engine reset [default])");
 
+module_param_named_unsafe(vbt_firmware, i915.vbt_firmware, charp, 0400);
+MODULE_PARM_DESC(vbt_firmware,
+                 "Load VBT from specified file under /lib/firmware");
+
 #if IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR)
 module_param_named(error_capture, i915.error_capture, bool, 0600);
 MODULE_PARM_DESC(error_capture,
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index febbfdbd30bd..ac844709c97e 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -28,6 +28,7 @@
 #include <linux/cache.h> /* for __read_mostly */
 
 #define I915_PARAMS_FOR_EACH(func) \
+        func(char *, vbt_firmware); \
         func(int, modeset); \
         func(int, panel_ignore_lid); \
         func(int, semaphores); \
diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index 2bd03001cc70..98154efcb2f4 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -27,6 +27,7 @@
 
 #include <linux/acpi.h>
 #include <linux/dmi.h>
+#include <linux/firmware.h>
 #include <acpi/video.h>
 
 #include <drm/drmP.h>
@@ -829,6 +830,10 @@ void intel_opregion_unregister(struct drm_i915_private *dev_priv)
                 memunmap(opregion->rvda);
                 opregion->rvda = NULL;
         }
+        if (opregion->vbt_firmware) {
+                kfree(opregion->vbt_firmware);
+                opregion->vbt_firmware = NULL;
+        }
         opregion->header = NULL;
         opregion->acpi = NULL;
         opregion->swsci = NULL;
@@ -912,6 +917,43 @@ static const struct dmi_system_id intel_no_opregion_vbt[] = {
         { }
 };
 
+static int intel_load_vbt_firmware(struct drm_i915_private *dev_priv)
+{
+        struct intel_opregion *opregion = &dev_priv->opregion;
+        const struct firmware *fw = NULL;
+        const char *name = i915.vbt_firmware;
+        int ret;
+
+        if (!name || !*name)
+                return -ENOENT;
+
+        ret = request_firmware(&fw, name, &dev_priv->drm.pdev->dev);
+        if (ret) {
+                DRM_ERROR("Requesting VBT firmware \"%s\" failed (%d)\n",
+                          name, ret);
+                return ret;
+        }
+
+        if (intel_bios_is_valid_vbt(fw->data, fw->size)) {
+                opregion->vbt_firmware = kmemdup(fw->data, fw->size, GFP_KERNEL);
+                if (opregion->vbt_firmware) {
+                        DRM_DEBUG_KMS("Found valid VBT firmware \"%s\"\n", name);
+                        opregion->vbt = opregion->vbt_firmware;
+                        opregion->vbt_size = fw->size;
+                        ret = 0;
+                } else {
+                        ret = -ENOMEM;
+                }
+        } else {
+                DRM_DEBUG_KMS("Invalid VBT firmware \"%s\"\n", name);
+                ret = -EINVAL;
+        }
+
+        release_firmware(fw);
+
+        return ret;
+}
+
 int intel_opregion_setup(struct drm_i915_private *dev_priv)
 {
         struct intel_opregion *opregion = &dev_priv->opregion;
@@ -974,6 +1016,9 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
         if (mboxes & MBOX_ASLE_EXT)
                 DRM_DEBUG_DRIVER("ASLE extension supported\n");
 
+        if (intel_load_vbt_firmware(dev_priv) == 0)
+                goto out;
+
         if (dmi_check_system(intel_no_opregion_vbt))
                 goto out;