[PATCH 3/4] amdgpu: resize BAR0 to the maximum available size, even if it doesn't cover VRAM (v6)

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

From: Darren Salt <devspam@moreofthesa.me.uk>

This allows BAR0 resizing to be done for cards which don't advertise support
for a size large enough to cover the VRAM but which do advertise at least
one size larger than the default. For example, my RX 5600 XT, which
advertises 256MB, 512MB and 1GB.

[v6] (chk) Reduce to only the necessary functionality

[v5] Drop the retry loop…

[v4] Use bit ops to find sizes to try.

[v3] Don't use pci_rebar_get_current_size().

[v2] Rewritten to use PCI helper functions; some extra log text.

Signed-off-by: Darren Salt <devspam@moreofthesa.me.uk>
Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 70acd673e3f2..da78746174f5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -1089,7 +1089,7 @@ void amdgpu_device_wb_free(struct amdgpu_device *adev, u32 wb)
  */
 int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
 {
-	u32 rbar_size = pci_rebar_bytes_to_size(adev->gmc.real_vram_size);
+	int rbar_size = pci_rebar_bytes_to_size(adev->gmc.real_vram_size);
 	struct pci_bus *root;
 	struct resource *res;
 	unsigned i;
@@ -1120,6 +1120,10 @@ int amdgpu_device_resize_fb_bar(struct amdgpu_device *adev)
 	if (!res)
 		return 0;
 
+	/* Limit the BAR size to what is available */
+	rbar_size = min(fls(pci_rebar_get_possible_sizes(adev->pdev, 0)) - 1,
+			rbar_size);
+
 	/* Disable memory decoding while we change the BAR addresses and size */
 	pci_read_config_word(adev->pdev, PCI_COMMAND, &cmd);
 	pci_write_config_word(adev->pdev, PCI_COMMAND,
-- 
2.25.1