[Intel-gfx] [PATCH RESEND 4/4] drm/i915/opregion: let user specify override VBT via firmware load

[Jani Nikula]

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.

References: https://bugs.freedesktop.org/show_bug.cgi?id=97822#c83
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/i915/i915_params.c    |  4 ++++
 drivers/gpu/drm/i915/i915_params.h    |  1 +
 drivers/gpu/drm/i915/intel_opregion.c | 40 +++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index b6a7e363d076..6d5d334f50b1 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -115,6 +115,10 @@ MODULE_PARM_DESC(vbt_sdvo_panel_type,
 	"Override/Ignore selection of SDVO panel mode in the VBT "
 	"(-2=ignore, -1=auto [default], index in VBT BIOS table)");
 
+module_param_named_unsafe(vbt_firmware, i915.vbt_firmware, charp, 0400);
+MODULE_PARM_DESC(vbt_firmware,
+		 "Load VBT from specified file under /lib/firmware");
+
 module_param_named_unsafe(reset, i915.reset, bool, 0600);
 MODULE_PARM_DESC(reset, "Attempt GPU resets (default: true)");
 
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index 34148cc8637c..0aeb106e06af 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 d44465190dc1..7cbd801516ab 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>
@@ -912,6 +913,42 @@ 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 = kmemdup(fw->data, fw->size, GFP_KERNEL);
+		if (opregion->vbt) {
+			DRM_DEBUG_KMS("Found valid VBT firmware \"%s\"\n", name);
+			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 +1011,9 @@ 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))
+		goto out;
+
 	if (dmi_check_system(intel_no_opregion_vbt))
 		goto out;
 
-- 
2.1.4