linux-kernel - [PATCH 1/1] amdgpu: use MMIO to init atombios if device is Thunderbolt / USB4 attached

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Date:   Sun, 14 Mar 2021 14:08:20 +0800
From:   Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
To:     linux-kernel@...r.kernel.org
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        amd-gfx@...ts.freedesktop.org
Subject: [PATCH 1/1] amdgpu: use MMIO to init atombios if device is
 Thunderbolt / USB4 attached

When using some Thunderbolt hosts using BIOS-assisted PCI enumeration
with IO BAR assigned, we get an atombios timeout, such as:

[drm:atom_op_jump [amdgpu]] *ERROR* atombios stuck in loop for more than 20secs aborting
[drm:amdgpu_atom_execute_table_locked [amdgpu]] *ERROR* atombios stuck executing B456 (len 304, WS 4, PS 0) @ 0xB51B
[drm:amdgpu_atom_execute_table_locked [amdgpu]] *ERROR* atombios stuck executing B104 (len 183, WS 0, PS 8) @ 0xB17E
amdgpu 0000:08:00.0: amdgpu: gpu post error!
amdgpu 0000:08:00.0: amdgpu: Fatal error during GPU init
amdgpu: probe of 0000:08:00.0 failed with error -22

A workaround is to use MMIO to access ATOMBIOS when device is
Thunderbolt / USB4 attached.
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
index 86add0f4e..5d16ec10d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
@@ -1999,11 +1999,15 @@ int amdgpu_atombios_init(struct amdgpu_device *adev)
 	atom_card_info->reg_read = cail_reg_read;
 	atom_card_info->reg_write = cail_reg_write;
 	/* needed for iio ops */
-	if (adev->rio_mem) {
+	if (adev->rio_mem && !pci_is_thunderbolt_attached(adev->pdev)) {
 		atom_card_info->ioreg_read = cail_ioreg_read;
 		atom_card_info->ioreg_write = cail_ioreg_write;
 	} else {
-		DRM_DEBUG("PCI I/O BAR is not found. Using MMIO to access ATOM BIOS\n");
+		if (pci_is_thunderbolt_attached(adev->pdev))
+			DRM_DEBUG("Device is attached via Thunderbolt / USB4. Using MMIO to access ATOM BIOS\n");
+		else
+			DRM_DEBUG("PCI I/O BAR is not found. Using MMIO to access ATOM BIOS\n");
+
 		atom_card_info->ioreg_read = cail_reg_read;
 		atom_card_info->ioreg_write = cail_reg_write;
 	}
-- 
2.30.2