[PATCH 6/8] amdgpu: allow overriding of the GPU's list of supported BAR sizes (v3)

[Darren Salt]

Some cards don't advertise a BAR size which covers all of the VRAM.

Mine, a Sapphire RX 5600 XT Pulse, advertises only 256MB, 512MB and 1GB.
Despite this, it appears to work fine with the full 6GB visible via an 8GB
BAR.

v3: changed implementation due to changes in preceding patches.

v2: different option controlling this due to a dropped patch.
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  8 ++++++--
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    | 10 ++++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 0b17e758e3f1..93285ec7bfc3 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -202,6 +202,7 @@ static const bool __maybe_unused no_system_mem_limit;
 extern int amdgpu_tmz;
 extern int amdgpu_reset_method;
 extern int amdgpu_max_bar_size;
+extern bool amdgpu_override_bar_sizes;
 
 #ifdef CONFIG_DRM_AMDGPU_SI
 extern int amdgpu_si_support;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 125aca52e25d..8490a96ee25e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -1151,7 +1151,11 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
 	if (!res)
 		return 0;
 
-	available_sizes = pci_rebar_get_possible_sizes(adev->pdev, 0);
+	if (amdgpu_override_bar_sizes)
+		available_sizes = ~(-1 << rbar_size) & ~0xFF;
+	else
+		available_sizes = pci_rebar_get_possible_sizes(adev->pdev, 0);
+
 	if (max_size >= 0) {
 		/* Cause larger sizes to be ignored unless that would leave
 		 * no advertised sizes (which shouldn't happen).
@@ -1188,7 +1192,7 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
 
 	pci_release_resource(adev->pdev, 0);
 
-	r = pci_resize_resource(adev->pdev, 0, rbar_size, false);
+	r = pci_resize_resource(adev->pdev, 0, rbar_size, amdgpu_override_bar_sizes);
 	if (r == -ENOTSUPP) {
 		dev_info(adev->dev, "BAR resizing not supported.");
 	} else if (r == -ENOSPC) {
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index dd2dc992ed13..59f6b95f0875 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -162,6 +162,7 @@ int amdgpu_tmz;
 int amdgpu_reset_method = -1; /* auto */
 int amdgpu_num_kcq = -1;
 int amdgpu_max_bar_size = -1;
+bool amdgpu_override_bar_sizes = false;
 
 struct amdgpu_mgpu_info mgpu_info = {
 	.mutex = __MUTEX_INITIALIZER(mgpu_info.mutex),
@@ -816,6 +817,15 @@ module_param_named(num_kcq, amdgpu_num_kcq, int, 0444);
 module_param_named(max_bar_size, amdgpu_max_bar_size, int, 0444);
 MODULE_PARM_DESC(max_bar_size, "Maximum FB BAR size, log2(megabytes) (default = -1, meaning unlimited; minimum is 8 for 256MB).");
 
+/**
+ * DOC: amdgpu_override_bar_sizes (int)
+ * A blunt instrument for ignoring the listed BAR sizes.
+ * This is intended to handle VBIOSes which list the wrong set of sizes but which aren't recognised as such by the kernel.
+ * Disabled by default.
+ */
+module_param_named(override_bar_sizes, amdgpu_override_bar_sizes, bool, 0444);
+MODULE_PARM_DESC(override_bar_sizes, "Ignore VBIOS supported BAR sizes, for where the list is wrong. (Disabled by default.)");
+
 static const struct pci_device_id pciidlist[] = {
 #ifdef  CONFIG_DRM_AMDGPU_SI
 	{0x1002, 0x6780, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_TAHITI},
-- 
2.20.1