[RFC, drm-misc-next v4 4/9] drm/amdgpu: Implement .be_primary() callback

[Sui Jingfeng <sui.jingfeng@linux.dev>]

From: Sui Jingfeng <suijingfeng@loongson.cn>

On a machine with multiple GPUs, a Linux user has no control over which one
is primary at boot time. This patch tries to solve the mentioned problem by
implementing the .be_primary() callback. Pass amdgpu.modeset=10 on the
kernel cmd line if you really want the device bound by amdgpu drm driver to
be the primary video adapter, no matter what VGAARB say.

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian Konig <christian.koenig@amd.com>
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 11 ++++++++++-
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    | 13 ++++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index ecc4564ceac0..59bde6972a8b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3507,6 +3507,14 @@ static void amdgpu_device_set_mcbp(struct amdgpu_device *adev)
 		DRM_INFO("MCBP is enabled\n");
 }
 
+static bool amdgpu_want_to_be_primary(struct pci_dev *pdev)
+{
+	if (amdgpu_modeset == 10)
+		return true;
+
+	return false;
+}
+
 /**
  * amdgpu_device_init - initialize the driver
  *
@@ -3916,7 +3924,8 @@ int amdgpu_device_init(struct amdgpu_device *adev,
 	 * 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_want_to_be_primary);
 
 	px = amdgpu_device_supports_px(ddev);
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 81edf66dbea8..2592e24ce62c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -118,6 +118,7 @@
 #define KMS_DRIVER_MINOR	54
 #define KMS_DRIVER_PATCHLEVEL	0
 
+int amdgpu_modeset = -1;
 unsigned int amdgpu_vram_limit = UINT_MAX;
 int amdgpu_vis_vram_limit;
 int amdgpu_gart_size = -1; /* auto */
@@ -223,6 +224,13 @@ struct amdgpu_watchdog_timer amdgpu_watchdog_timer = {
 	.period = 0x0, /* default to 0x0 (timeout disable) */
 };
 
+/**
+ * DOC: modeset (int)
+ * Disable/Enable kernel modesetting (1 = enable, 0 = disable, -1 = auto (default)).
+ */
+MODULE_PARM_DESC(modeset, "Disable/Enable kernel modesetting");
+module_param_named(modeset, amdgpu_modeset, int, 0600);
+
 /**
  * DOC: vramlimit (int)
  * Restrict the total amount of VRAM in MiB for testing.  The default is 0 (Use full VRAM).
@@ -2872,7 +2880,10 @@ static int __init amdgpu_init(void)
 {
 	int r;
 
-	if (drm_firmware_drivers_only())
+	if (drm_firmware_drivers_only() && amdgpu_modeset == -1)
+		return -EINVAL;
+
+	if (amdgpu_modeset == 0)
 		return -EINVAL;
 
 	r = amdgpu_sync_init();
-- 
2.34.1