x86: tnc: Remove IGD and SDVO devices from driver model

With recent DM PCI changes to vesa_fb driver, external graphics
card does not work any more. This is because: after setting the
function disable bit, IGD and SDVO devices will disappear in the
PCI configuration space. This however creates an inconsistent state
from a driver model PCI controller point of view, as these two PCI
devices are still attached to its parent's child device list as
maintained by the driver model. Some driver model PCI APIs like
dm_pci_find_class() used in the vesa_fb driver, are referring to
the list to speed up the finding process instead of re-enumerating
the whole PCI bus, so it gets the stale cached data which is wrong.

To fix this, manually remove these two devices.

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

arch/x86/cpu/queensbay/tnc.c

@@ -6,6 +6,7 @@
 
 #include <common.h>
 #include <dm.h>
+#include <dm/device-internal.h>
 #include <pci.h>
 #include <asm/io.h>
 #include <asm/irq.h>
@@ -53,6 +54,41 @@ static int __maybe_unused disable_igd(void)
 	dm_pci_write_config32(igd, IGD_FD, FUNC_DISABLE);
 	dm_pci_write_config32(sdvo, IGD_FD, FUNC_DISABLE);
 
+	/*
+	 * After setting the function disable bit, IGD and SDVO devices will
+	 * disappear in the PCI configuration space. This however creates an
+	 * inconsistent state from a driver model PCI controller point of view,
+	 * as these two PCI devices are still attached to its parent's child
+	 * device list as maintained by the driver model. Some driver model PCI
+	 * APIs like dm_pci_find_class(), are referring to the list to speed up
+	 * the finding process instead of re-enumerating the whole PCI bus, so
+	 * it gets the stale cached data which is wrong.
+	 *
+	 * Note x86 PCI enueration normally happens twice, in pre-relocation
+	 * phase and post-relocation. One option might be to call disable_igd()
+	 * in one of the pre-relocation initialization hooks so that it gets
+	 * disabled in the first round, and when it comes to the second round
+	 * driver model PCI will construct a correct list. Unfortunately this
+	 * does not work as Intel FSP is used on this platform to perform low
+	 * level initialization, and fsp_init_phase_pci() is called only once
+	 * in the post-relocation phase. If we disable IGD and SDVO devices,
+	 * fsp_init_phase_pci() simply hangs and never returns.
+	 *
+	 * So the only option we have is to manually remove these two devices.
+	 */
+	ret = device_remove(igd);
+	if (ret)
+		return ret;
+	ret = device_unbind(igd);
+	if (ret)
+		return ret;
+	ret = device_remove(sdvo);
+	if (ret)
+		return ret;
+	ret = device_unbind(sdvo);
+	if (ret)
+		return ret;
+
 	return 0;
 }