From 48b733d99b0d8db01fcf55d7ae31f69510fb1a4a Mon Sep 17 00:00:00 2001 From: Alex Deucher Date: Thu, 27 Feb 2025 12:31:28 -0500 Subject: [PATCH] drm/amdgpu: add rebar parameter Add a new parameter to disable BAR resizing. Note that this only disables the driver from attempting to resize the BAR, The BIOS may have resized the BAR at boot. Some teams have found this useful in debugging P2P DMA issues on systems where the available MMIO space did not allow for all of the GPUs present to resize their BARs. Reviewed-by: Mario Limonciello Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/amdgpu/amdgpu.h | 1 + drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 3 +++ drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 11 +++++++++++ 3 files changed, 15 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h index 9a9e5249c63f..8316f93c1cce 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h @@ -266,6 +266,7 @@ extern int amdgpu_umsch_mm_fwlog; extern int amdgpu_user_partt_mode; extern int amdgpu_agp; +extern int amdgpu_rebar; extern int amdgpu_wbrf; diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c index 7525128f971f..f4a01704effc 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c @@ -1680,6 +1680,9 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev) if (amdgpu_sriov_vf(adev)) return 0; + if (!amdgpu_rebar) + return 0; + /* resizing on Dell G5 SE platforms causes problems with runtime pm */ if ((amdgpu_runtime_pm != 0) && adev->pdev->vendor == PCI_VENDOR_ID_ATI && diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c index 26bf896f1444..2ca04d6aaa82 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c @@ -238,6 +238,7 @@ int amdgpu_agp = -1; /* auto */ int amdgpu_wbrf = -1; int amdgpu_damage_clips = -1; /* auto */ int amdgpu_umsch_mm_fwlog; +int amdgpu_rebar = -1; /* auto */ DECLARE_DYNDBG_CLASSMAP(drm_debug_classes, DD_CLASS_TYPE_DISJOINT_BITS, 0, "DRM_UT_CORE", @@ -1096,6 +1097,16 @@ MODULE_PARM_DESC(wbrf, "Enable Wifi RFI interference mitigation (0 = disabled, 1 = enabled, -1 = auto(default)"); module_param_named(wbrf, amdgpu_wbrf, int, 0444); +/** + * DOC: rebar (int) + * Allow BAR resizing. Disable this to prevent the driver from attempting + * to resize the BAR if the GPU supports it and there is available MMIO space. + * Note that this just prevents the driver from resizing the BAR. The BIOS + * may have already resized the BAR at boot time. + */ +MODULE_PARM_DESC(rebar, "Resizable BAR (-1 = auto (default), 0 = disable, 1 = enable)"); +module_param_named(rebar, amdgpu_rebar, int, 0444); + /* These devices are not supported by amdgpu. * They are supported by the mach64, r128, radeon drivers */ -- 2.25.1