[Intel-gfx] [PATCH v3] 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.

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 at intel.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h       |  1 +
 drivers/gpu/drm/i915/i915_params.c    |  4 ++++
 drivers/gpu/drm/i915/i915_params.h    |  1 +
 drivers/gpu/drm/i915/intel_opregion.c | 45 +++++++++++++++++++++++++++++++++++
 4 files changed, 51 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bde554eb2257..b200faa177ca 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -641,6 +641,7 @@ 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 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..a71b1c42aad8 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;
 
-- 
2.11.0