linux-kernel - [PATCH v3 5/9] drm/amdgpu: Implement the is_primary_gpu callback of vga_client

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Message-Id: <20230711164310.791756-6-sui.jingfeng@linux.dev>
Date:   Wed, 12 Jul 2023 00:43:06 +0800
From:   Sui Jingfeng <sui.jingfeng@...ux.dev>
To:     David Airlie <airlied@...il.com>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        kvm@...r.kernel.org, linux-fbdev@...r.kernel.org,
        Sui Jingfeng <suijingfeng@...ngson.cn>,
        Alex Deucher <alexander.deucher@....com>,
        Christian Konig <christian.koenig@....com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH v3 5/9] drm/amdgpu: Implement the is_primary_gpu callback of vga_client_register()

From: Sui Jingfeng <suijingfeng@...ngson.cn>

[why]

The vga_is_firmware_default() function defined in drivers/pci/vgaarb.c is
arch-dependent, it's a dummy on non-x86 architectures. This made VGAARB
lost an important condition for the arbitration on non-x86 platform. The
rules about which GPU is (or should be) the primary display device get used
by userspace are obscure on non-x86 platform, let's made the things clear.

[how]

The device that owns the firmware framebuffer should be the default boot
device. This patch adds an arch-independent function to implement this
rule. The vgaarb subsystem will call back to amdgpu_is_primary_gpu() when
drm/amdgpu is bound to an AMDGPU device successfully.

Cc: Alex Deucher <alexander.deucher@....com>
Cc: Christian Konig <christian.koenig@....com>
Cc: Mario Limonciello <mario.limonciello@....com>
Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index d98f0801ac77..b638eff58636 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3690,6 +3690,15 @@ static void amdgpu_device_set_mcbp(struct amdgpu_device *adev)
 		DRM_INFO("MCBP is enabled\n");
 }
 
+static bool amdgpu_is_primary_gpu(struct pci_dev *pdev)
+{
+	struct drm_device *dev = pci_get_drvdata(pdev);
+	struct amdgpu_device *adev = drm_to_adev(dev);
+	struct amdgpu_gmc *gmc = &adev->gmc;
+
+	return drm_aperture_contain_firmware_fb(gmc->aper_base, gmc->aper_size);
+}
+
 /**
  * amdgpu_device_init - initialize the driver
  *
@@ -4103,7 +4112,8 @@ int amdgpu_device_init(struct amdgpu_device *adev,
 	/* this will fail for cards that aren't VGA class devices, just
 	 * ignore it */
 	if ((adev->pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
-		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode, NULL);
+		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode,
+				    amdgpu_is_primary_gpu);
 
 	px = amdgpu_device_supports_px(ddev);
 
-- 
2.25.1