[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 c0e3e402023e..1bf21231a628 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -195,6 +195,7 @@ static const bool debug_evictions; /* = false */
 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 ce3b8f8fea0c..0f05a75be34e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -954,7 +954,11 @@ 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).
@@ -995,7 +999,7 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
 	     rbar_size >= 0;
 	     rbar_size = fls(available_sizes & ~(-1 << rbar_size)) - 1
 	    ) {
-		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 == 0) {
 			break;
 		} else if (r == -ENOTSUPP) {
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 74baa8dafa5f..983f80bbe49b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -151,6 +151,7 @@ int amdgpu_force_asic_type = -1;
 int amdgpu_tmz = 0;
 int amdgpu_reset_method = -1; /* auto */
 int amdgpu_max_bar_size = -1;
+bool amdgpu_override_bar_sizes = false;
 
 struct amdgpu_mgpu_info mgpu_info = {
 	.mutex = __MUTEX_INITIALIZER(mgpu_info.mutex),
@@ -774,6 +775,15 @@ module_param_named(reset_method, amdgpu_reset_method, 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