mach-snapdragon: fixup USB nodes

We don't support USB super-speed in U-Boot yet, we lack the SS PHY
drivers, however from my testing even with a PHY driver there seem to be
other issues when talking to super-speed peripherals.

In pursuit of maintaining upstream DT compatibility, and simplifying
porting for new devices, let's implement the DT fixups necessary to
configure USB in high-speed only mode at runtime. The pattern is
identical for all Qualcomm boards that use the Synaptics DWC3
controller:

* Add an additional property on the Qualcomm wrapper node
* Remove the super-speed phy phandle and phy-name entries.

Acked-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>

arch/arm/mach-snapdragon/Makefile

@@ -3,3 +3,4 @@
 # (C) Copyright 2015 Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
 
 obj-y += board.o
+obj-$(CONFIG_OF_LIVE) += of_fixup.o

arch/arm/mach-snapdragon/board.c

@@ -28,6 +28,8 @@
 #include <usb.h>
 #include <sort.h>
 
+#include "qcom-priv.h"
+
 DECLARE_GLOBAL_DATA_PTR;
 
 static struct mm_region rbx_mem_map[CONFIG_NR_DRAM_BANKS + 2] = { { 0 } };
@@ -160,6 +162,7 @@ void __weak qcom_board_init(void)
 int board_init(void)
 {
 	show_psci_version();
+	qcom_of_fixup_nodes();
 	qcom_board_init();
 	return 0;
 }

arch/arm/mach-snapdragon/of_fixup.c

@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * OF_LIVE devicetree fixup.
+ *
+ * This file implements runtime fixups for Qualcomm DT to improve
+ * compatibility with U-Boot. This includes adjusting the USB nodes
+ * to only use USB high-speed, as well as remapping volume buttons
+ * to behave as up/down for navigating U-Boot.
+ *
+ * We use OF_LIVE for this rather than early FDT fixup for a couple
+ * of reasons: it has a much nicer API, is most likely more efficient,
+ * and our changes are only applied to U-Boot. This allows us to use a
+ * DT designed for Linux, run U-Boot with a modified version, and then
+ * boot Linux with the original FDT.
+ *
+ * Copyright (c) 2024 Linaro Ltd.
+ *   Author: Caleb Connolly <caleb.connolly@linaro.org>
+ */
+
+#include <dt-bindings/input/linux-event-codes.h>
+#include <dm/of_access.h>
+#include <dm/of.h>
+#include <fdt_support.h>
+#include <linux/errno.h>
+#include <time.h>
+
+/* U-Boot only supports USB high-speed mode on Qualcomm platforms with DWC3
+ * USB controllers. Rather than requiring source level DT changes, we fix up
+ * DT here. This improves compatibility with upstream DT and simplifies the
+ * porting process for new devices.
+ */
+static int fixup_qcom_dwc3(struct device_node *glue_np)
+{
+	struct device_node *dwc3;
+	int ret, len, hsphy_idx = 1;
+	const __be32 *phandles;
+	const char *second_phy_name;
+
+	debug("Fixing up %s\n", glue_np->name);
+
+	/* Tell the glue driver to configure the wrapper for high-speed only operation */
+	ret = of_write_prop(glue_np, "qcom,select-utmi-as-pipe-clk", 0, NULL);
+	if (ret) {
+		log_err("Failed to add property 'qcom,select-utmi-as-pipe-clk': %d\n", ret);
+		return ret;
+	}
+
+	/* Find the DWC3 node itself */
+	dwc3 = of_find_compatible_node(glue_np, NULL, "snps,dwc3");
+	if (!dwc3) {
+		log_err("Failed to find dwc3 node\n");
+		return -ENOENT;
+	}
+
+	phandles = of_get_property(dwc3, "phys", &len);
+	len /= sizeof(*phandles);
+	if (len == 1) {
+		log_debug("Only one phy, not a superspeed controller\n");
+		return 0;
+	}
+
+	/* Figure out if the superspeed phy is present and if so then which phy is it? */
+	ret = of_property_read_string_index(dwc3, "phy-names", 1, &second_phy_name);
+	if (ret == -ENODATA) {
+		log_debug("Only one phy, not a super-speed controller\n");
+		return 0;
+	} else if (ret) {
+		log_err("Failed to read second phy name: %d\n", ret);
+		return ret;
+	}
+
+	if (!strncmp("usb3-phy", second_phy_name, strlen("usb3-phy"))) {
+		log_debug("Second phy isn't superspeed (is '%s') assuming first phy is SS\n",
+			  second_phy_name);
+		hsphy_idx = 0;
+	}
+
+	/* Overwrite the "phys" property to only contain the high-speed phy */
+	ret = of_write_prop(dwc3, "phys", sizeof(*phandles), phandles + hsphy_idx);
+	if (ret) {
+		log_err("Failed to overwrite 'phys' property: %d\n", ret);
+		return ret;
+	}
+
+	/* Overwrite "phy-names" to only contain a single entry */
+	ret = of_write_prop(dwc3, "phy-names", strlen("usb2-phy"), "usb2-phy");
+	if (ret) {
+		log_err("Failed to overwrite 'phy-names' property: %d\n", ret);
+		return ret;
+	}
+
+	ret = of_write_prop(dwc3, "maximum-speed", strlen("high-speed"), "high-speed");
+	if (ret) {
+		log_err("Failed to set 'maximum-speed' property: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void fixup_usb_nodes(void)
+{
+	struct device_node *glue_np = NULL;
+	int ret;
+
+	while ((glue_np = of_find_compatible_node(glue_np, NULL, "qcom,dwc3"))) {
+		ret = fixup_qcom_dwc3(glue_np);
+		if (ret)
+			log_warning("Failed to fixup node %s: %d\n", glue_np->name, ret);
+	}
+}
+
+#define time_call(func, ...) \
+	do { \
+		u64 start = timer_get_us(); \
+		func(__VA_ARGS__); \
+		debug(#func " took %lluus\n", timer_get_us() - start); \
+	} while (0)
+
+void qcom_of_fixup_nodes(void)
+{
+	time_call(fixup_usb_nodes);
+}

arch/arm/mach-snapdragon/qcom-priv.h

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef __QCOM_PRIV_H__
+#define __QCOM_PRIV_H__
+
+#if CONFIG_IS_ENABLED(OF_LIVE)
+/**
+ * qcom_of_fixup_nodes() - Fixup Qualcomm DT nodes
+ *
+ * Adjusts nodes in the live tree to improve compatibility with U-Boot.
+ */
+void qcom_of_fixup_nodes(void);
+#else
+static inline void qcom_of_fixup_nodes(void)
+{
+	log_debug("Unable to dynamically fixup USB nodes, please enable CONFIG_OF_LIVE\n");
+}
+#endif /* OF_LIVE */
+
+#endif /* __QCOM_PRIV_H__ */