[RFC, drm-misc-next v4 7/9] drm/ast: Register as a VGA client by calling vga_client_register()

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

From: Sui Jingfeng <suijingfeng@loongson.cn>

Becasuse the display controller in the ASpeed BMC chip is a VGA-compatible
device, the software programming guide of AST2400 say that it is fully
IBM VGA compliant. Thus, it should also participate in the arbitration.

Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
---
 drivers/gpu/drm/ast/ast_drv.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/ast/ast_drv.c b/drivers/gpu/drm/ast/ast_drv.c
index e1224ef4ad83..1349f7bb5dfb 100644
--- a/drivers/gpu/drm/ast/ast_drv.c
+++ b/drivers/gpu/drm/ast/ast_drv.c
@@ -28,6 +28,7 @@
 
 #include <linux/module.h>
 #include <linux/pci.h>
+#include <linux/vgaarb.h>
 
 #include <drm/drm_aperture.h>
 #include <drm/drm_atomic_helper.h>
@@ -89,6 +90,34 @@ static const struct pci_device_id ast_pciidlist[] = {
 
 MODULE_DEVICE_TABLE(pci, ast_pciidlist);
 
+static bool ast_want_to_be_primary(struct pci_dev *pdev)
+{
+	if (ast_modeset == 10)
+		return true;
+
+	return false;
+}
+
+static unsigned int ast_vga_set_decode(struct pci_dev *pdev, bool state)
+{
+	struct drm_device *drm = pci_get_drvdata(pdev);
+	struct ast_device *ast = to_ast_device(drm);
+	unsigned int decode;
+
+	if (state) {
+		/* Enable standard VGA decode and Enable normal VGA decode */
+		ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0xa1, 0x04);
+
+		decode = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM |
+			 VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
+	} else {
+		ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0xa1, 0x07);
+		decode = VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
+	}
+
+	return decode;
+}
+
 static int ast_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	struct ast_device *ast;
@@ -112,6 +141,8 @@ static int ast_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (ret)
 		return ret;
 
+	vga_client_register(pdev, ast_vga_set_decode, ast_want_to_be_primary);
+
 	drm_fbdev_generic_setup(dev, 32);
 
 	return 0;
-- 
2.34.1