x86: pci: Allow binding of some devices before relocation

At present only bridge devices are bound before relocation, to save space
in pre-relocation memory. In some cases we do actually want to bind a
device, e.g. because it provides the console UART. Add a devicetree
binding to support this.

Use the PCI_VENDEV() macro to encode the cell value. This is present in
U-Boot but not used, so move it to the binding header-file.

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

doc/device-tree-bindings/pci/x86-pci.txt

@@ -20,6 +20,10 @@ For PCI devices the following optional property is available:
 	output to be lost. This should not generally be used in production code,
 	although it is often harmless.
 
+- u-boot,pci-pre-reloc : List of vendor/device IDs to bind before relocation, even
+	if they are not bridges. This is useful if the device is needed (e.g. a
+	UART). The format is 0xvvvvdddd where d is the device ID and v is the
+	vendor ID.
 
 Example:
 
@@ -32,7 +36,8 @@ pci {
 		0x42000000 0x0 0xb0000000 0xb0000000 0 0x10000000
 		0x01000000 0x0 0x1000 0x1000 0 0xefff>;
 	u-boot,skip-auto-config-until-reloc;
-
+	u-boot,pci-pre-reloc = <
+		PCI_VENDEV(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_APL_UART2)>;
 
 	serial: serial@18,2 {
 		reg = <0x0200c210 0 0 0 0>;

drivers/pci/pci-uclass.c

@@ -21,6 +21,7 @@
 #if defined(CONFIG_X86) && defined(CONFIG_HAVE_FSP)
 #include <asm/fsp/fsp_support.h>
 #endif
+#include <dt-bindings/pci/pci.h>
 #include <linux/delay.h>
 #include "pci_internal.h"
 
@@ -681,6 +682,34 @@ static bool pci_match_one_id(const struct pci_device_id *id,
 	return false;
 }
 
+/**
+ * pci_need_device_pre_reloc() - Check if a device should be bound
+ *
+ * This checks a list of vendor/device-ID values indicating devices that should
+ * be bound before relocation.
+ *
+ * @bus: Bus to check
+ * @vendor: Vendor ID to check
+ * @device: Device ID to check
+ * @return true if the vendor/device is in the list, false if not
+ */
+static bool pci_need_device_pre_reloc(struct udevice *bus, uint vendor,
+				      uint device)
+{
+	u32 vendev;
+	int index;
+
+	for (index = 0;
+	     !dev_read_u32_index(bus, "u-boot,pci-pre-reloc", index,
+				 &vendev);
+	     index++) {
+		if (vendev == PCI_VENDEV(vendor, device))
+			return true;
+	}
+
+	return false;
+}
+
 /**
  * pci_find_and_bind_driver() - Find and bind the right PCI driver
  *
@@ -769,7 +798,9 @@ static int pci_find_and_bind_driver(struct udevice *parent,
 	 * precious memory space as on some platforms as that space is pretty
 	 * limited (ie: using Cache As RAM).
 	 */
-	if (!(gd->flags & GD_FLG_RELOC) && !bridge)
+	if (!(gd->flags & GD_FLG_RELOC) && !bridge &&
+	    !pci_need_device_pre_reloc(parent, find_id->vendor,
+				       find_id->device))
 		return log_msg_ret("notbr", -EPERM);
 
 	/* Bind a generic driver so that the device can be used */

include/dt-bindings/pci/pci.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * This header provides common constants for PCI bindings.
+ */
+
+#ifndef _DT_BINDINGS_PCI_PCI_H
+#define _DT_BINDINGS_PCI_PCI_H
+
+/* Encode a vendor and device ID into a single cell */
+#define PCI_VENDEV(v, d)	(((v) << 16) | (d))
+
+#endif /* _DT_BINDINGS_PCI_PCI_H */

include/pci.h

@@ -578,7 +578,6 @@ typedef int pci_dev_t;
 #define PCI_MASK_BUS(bdf)	((bdf) & 0xffff)
 #define PCI_ADD_BUS(bus, devfn)	(((bus) << 16) | (devfn))
 #define PCI_BDF(b, d, f)	((b) << 16 | PCI_DEVFN(d, f))
-#define PCI_VENDEV(v, d)	(((v) << 16) | (d))
 #define PCI_ANY_ID		(~0)
 
 /* Convert from Linux format to U-Boot format */