[RFC, drm-misc-next v4 6/9] drm/loongson: 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 loongson.modeset=10 on the
kernel cmd line if you really want the device bound by loongson drm driver
to be the primary video adapter, no matter what VGAARB say.

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/gpu/drm/loongson/loongson_module.c |  2 +-
 drivers/gpu/drm/loongson/loongson_module.h |  1 +
 drivers/gpu/drm/loongson/lsdc_drv.c        | 10 +++++++++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/loongson/loongson_module.c b/drivers/gpu/drm/loongson/loongson_module.c
index d2a51bd395f6..12f2a453adff 100644
--- a/drivers/gpu/drm/loongson/loongson_module.c
+++ b/drivers/gpu/drm/loongson/loongson_module.c
@@ -9,7 +9,7 @@
 
 #include "loongson_module.h"
 
-static int loongson_modeset = -1;
+int loongson_modeset = -1;
 MODULE_PARM_DESC(modeset, "Disable/Enable modesetting");
 module_param_named(modeset, loongson_modeset, int, 0400);
 
diff --git a/drivers/gpu/drm/loongson/loongson_module.h b/drivers/gpu/drm/loongson/loongson_module.h
index 931c17521bf0..afff51e7f34f 100644
--- a/drivers/gpu/drm/loongson/loongson_module.h
+++ b/drivers/gpu/drm/loongson/loongson_module.h
@@ -6,6 +6,7 @@
 #ifndef __LOONGSON_MODULE_H__
 #define __LOONGSON_MODULE_H__
 
+extern int loongson_modeset;
 extern int loongson_vblank;
 extern struct pci_driver lsdc_pci_driver;
 
diff --git a/drivers/gpu/drm/loongson/lsdc_drv.c b/drivers/gpu/drm/loongson/lsdc_drv.c
index d10a28c2c494..7183b0666167 100644
--- a/drivers/gpu/drm/loongson/lsdc_drv.c
+++ b/drivers/gpu/drm/loongson/lsdc_drv.c
@@ -257,6 +257,14 @@ static unsigned int lsdc_vga_set_decode(struct pci_dev *pdev, bool state)
 	return VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
 }
 
+static bool lsdc_want_to_be_primary(struct pci_dev *pdev)
+{
+	if (loongson_modeset == 10)
+		return true;
+
+	return false;
+}
+
 static int lsdc_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	const struct lsdc_desc *descp;
@@ -289,7 +297,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	pci_set_drvdata(pdev, ddev);
 
-	vga_client_register(pdev, lsdc_vga_set_decode, NULL);
+	vga_client_register(pdev, lsdc_vga_set_decode, lsdc_want_to_be_primary);
 
 	drm_kms_helper_poll_init(ddev);
 
-- 
2.34.1