x86: Allow disabling IGD on Intel Queensbay

Add a Kconfig option to disable the Integrated Graphics Device (IGD)
so that it does not show in the PCI configuration space as a VGA
disaplay controller. This gives a chance for U-Boot to run PCI/PCIe
based graphics card's VGA BIOS and use that for the graphics console.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/queensbay/Kconfig

@@ -42,4 +42,12 @@ config CPU_ADDR_BITS
 	int
 	default 32
 
+config DISABLE_IGD
+	bool "Disable Integrated Graphics Device (IGD)"
+	help
+	  Disable the Integrated Graphics Device (IGD) so that it does not
+	  show in the PCI configuration space as a VGA disaplay controller.
+	  This gives a chance for U-Boot to run PCI/PCIe based graphics
+	  card's VGA BIOS and use that card for the graphics console.
+
 endif

arch/x86/cpu/queensbay/tnc.c

@@ -23,6 +23,16 @@ static void unprotect_spi_flash(void)
 	x86_pci_write_config32(TNC_LPC, 0xd8, bc);
 }
 
+static void __maybe_unused disable_igd(void)
+{
+	u32 gc;
+
+	gc = x86_pci_read_config32(TNC_IGD, IGD_GC);
+	gc &= ~GMS_MASK;
+	gc |= VGA_DISABLE;
+	x86_pci_write_config32(TNC_IGD, IGD_GC, gc);
+}
+
 int arch_cpu_init(void)
 {
 	int ret;
@@ -39,6 +49,15 @@ int arch_cpu_init(void)
 	return 0;
 }
 
+int arch_early_init_r(void)
+{
+#ifdef CONFIG_DISABLE_IGD
+	disable_igd();
+#endif
+
+	return 0;
+}
+
 void cpu_irq_init(void)
 {
 	struct tnc_rcba *rcba;

arch/x86/include/asm/arch-queensbay/tnc.h

@@ -7,6 +7,11 @@
 #ifndef _X86_ARCH_TNC_H_
 #define _X86_ARCH_TNC_H_
 
+/* IGD Control Register */
+#define IGD_GC		0x50
+#define VGA_DISABLE	0x00020000
+#define GMS_MASK	0x00700000
+
 /* Memory BAR Enable */
 #define MEM_BAR_EN	0x00000001
 

include/configs/crownbay.h

@@ -15,6 +15,7 @@
 
 #define CONFIG_SYS_MONITOR_LEN		(1 << 20)
 #define CONFIG_BOARD_EARLY_INIT_F
+#define CONFIG_ARCH_EARLY_INIT_R
 #define CONFIG_ARCH_MISC_INIT
 
 #define CONFIG_SMSC_LPC47M