From f839052fe72eaf8af8fcd8948f91bc917f866514 Mon Sep 17 00:00:00 2001
From: Mario Scheithauer <mario.scheithauer@siemens.com>
Date: Wed, 4 Sep 2019 09:40:44 +0200
Subject: mb/siemens/mc_apl5: Disable IGD if no EDID data available

To avoid possible panel failures due to incorrect timing settings for
PTN3460, the internal graphic device should be disabled.

Change-Id: Ie0b9ed99fb78461bb48d6f2ff328643cd8c2cd15
Signed-off-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35242
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
---
 .../siemens/mc_apl1/variants/mc_apl5/ptn3460.c     | 25 ++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/mainboard/siemens/mc_apl1/variants/mc_apl5/ptn3460.c b/src/mainboard/siemens/mc_apl1/variants/mc_apl5/ptn3460.c
index f6fed97551..2cc7dd4532 100644
--- a/src/mainboard/siemens/mc_apl1/variants/mc_apl5/ptn3460.c
+++ b/src/mainboard/siemens/mc_apl1/variants/mc_apl5/ptn3460.c
@@ -16,9 +16,32 @@
 #include <console/console.h>
 #include <hwilib.h>
 #include <device/i2c_simple.h>
+#include <device/pci_ops.h>
+#include <soc/pci_devs.h>
 #include <types.h>
 #include <variant/ptn3460.h>
 
+static void igd_disable(void)
+{
+	struct device *root_dev = pcidev_path_on_root(SA_DEVFN_ROOT);
+	uint8_t deven;
+	uint16_t ggc;
+
+	/* GMCH Graphics Control Register */
+	ggc = pci_read_config16(root_dev, 0x50);
+	/* Set size of Graphics Translation Table Memory (GGMS) [7:6]
+	 * to 0 and select 0 MB for Graphics Memory (GMS) [15:8]. */
+	ggc &= ~(0xffc0);
+	/* Disable IGD VGA (IVD). */
+	ggc |= 0x2;
+	pci_write_config16(root_dev, 0x50, ggc);
+	/* Device Enable Register */
+	deven = pci_read_config8(root_dev, 0x54);
+	/* Disable IGD device (D2F0EN). */
+	deven &= ~(0x10);
+	pci_write_config8(root_dev, 0x54, deven);
+}
+
 /**
  * This function sets up the DP2LVDS-converter to be used with the appropriate
  * lcd panel.
@@ -42,6 +65,8 @@ int ptn3460_init(const char *hwi_block)
 	/* Get all needed information from hwinfo block. */
 	if (hwilib_get_field(Edid, edid_data, sizeof(edid_data)) !=
 			sizeof(edid_data)) {
+		/* Disable IGD to avoid panel failures. */
+		igd_disable();
 		printk(BIOS_ERR, "LCD: No EDID data available in %s\n",
 				hwi_block);
 		return 1;
-- 
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