power: reset: Add qcom-dload-mode driver

Add a driver to manage download mode for Qualcomm SoCs. The driver can
force SoC to restart into a dump collection mode when panicking for
post-morten analysis, as controlled by
CONFIG_POWER_RESET_MSM_DOWNLOAD_MODE_DEFAULT. The driver also can reboot
into "emergency download mode," which restarts SoC into mode which
permits re-flashing storage via Qualcomm Sahara protocol.

Change-Id: I30c83bf020715b7a80c00faa19280aec7f708435
Signed-off-by: Elliot Berman <eberman@codeaurora.org>

drivers/power/reset/Kconfig

@@ -105,6 +105,25 @@ config POWER_RESET_MSM
 	help
 	  Power off and restart support for Qualcomm boards.
 
+config POWER_RESET_QCOM_DOWNLOAD_MODE
+	tristate "MSM download mode driver"
+	depends on ARCH_QCOM
+	help
+	  MSM boards support booting to special download modes after a restart.
+	  These modes could be a normal restart, restarting into a
+	  ramdump collection mode (CrashDump), or restarting into "emergency
+	  download mode".
+
+config POWER_RESET_QCOM_DOWNLOAD_MODE_DEFAULT
+	bool "MSM download mode enabled by default"
+	help
+	  A device with "download mode" enabled will upon an unexpected
+	  warm-restart enter a special debug mode that allows the user to
+	  "download" memory content over USB for offline postmortem analysis.
+	  The feature can be enabled/disabled on the kernel command line.
+
+	  Say Y here to enable "download mode" by default.
+
 config POWER_RESET_QCOM_PON
 	tristate "Qualcomm power-on driver"
 	depends on ARCH_QCOM

drivers/power/reset/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_POWER_RESET_GPIO) += gpio-poweroff.o
 obj-$(CONFIG_POWER_RESET_GPIO_RESTART) += gpio-restart.o
 obj-$(CONFIG_POWER_RESET_HISI) += hisi-reboot.o
 obj-$(CONFIG_POWER_RESET_MSM) += msm-poweroff.o
+obj-$(CONFIG_POWER_RESET_QCOM_DOWNLOAD_MODE) += qcom-dload-mode.o
 obj-$(CONFIG_POWER_RESET_QCOM_PON) += qcom-pon.o
 obj-$(CONFIG_POWER_RESET_OCELOT_RESET) += ocelot-reset.o
 obj-$(CONFIG_POWER_RESET_PIIX4_POWEROFF) += piix4-poweroff.o

drivers/power/reset/qcom-dload-mode.c

@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2020 The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/reboot.h>
+#include <linux/pm.h>
+#include <linux/qcom_scm.h>
+
+struct qcom_dload {
+	struct notifier_block panic_nb;
+	struct notifier_block reboot_nb;
+
+	bool in_panic;
+};
+
+static bool enable_dump =
+	IS_ENABLED(CONFIG_POWER_RESET_QCOM_DOWNLOAD_MODE_DEFAULT);
+static enum qcom_download_mode current_download_mode = QCOM_DOWNLOAD_NODUMP;
+
+static int set_download_mode(enum qcom_download_mode mode)
+{
+	current_download_mode = mode;
+	qcom_scm_set_download_mode(mode, 0);
+	return 0;
+}
+
+static int param_set_download_mode(const char *val,
+		const struct kernel_param *kp)
+{
+	int ret;
+
+	/* update enable_dump according to user input */
+	ret = param_set_bool(val, kp);
+	if (ret)
+		return ret;
+
+	set_download_mode(QCOM_DOWNLOAD_FULLDUMP);
+
+	return 0;
+}
+module_param_call(download_mode, param_set_download_mode, param_get_int,
+			&enable_dump, 0644);
+
+static int qcom_dload_panic(struct notifier_block *this, unsigned long event,
+			      void *ptr)
+{
+	struct qcom_dload *poweroff = container_of(this, struct qcom_dload,
+						     panic_nb);
+	poweroff->in_panic = true;
+	if (enable_dump)
+		set_download_mode(QCOM_DOWNLOAD_FULLDUMP);
+	return NOTIFY_OK;
+}
+
+static int qcom_dload_reboot(struct notifier_block *this, unsigned long event,
+			      void *ptr)
+{
+	char *cmd = ptr;
+	struct qcom_dload *poweroff = container_of(this, struct qcom_dload,
+						     reboot_nb);
+
+	/* Clean shutdown, disable dump mode to allow normal restart */
+	if (!poweroff->in_panic)
+		set_download_mode(QCOM_DOWNLOAD_NODUMP);
+
+	if (cmd) {
+		if (!strcmp(cmd, "edl"))
+			set_download_mode(QCOM_DOWNLOAD_EDL);
+		else if (!strcmp(cmd, "qcom_dload"))
+			set_download_mode(QCOM_DOWNLOAD_FULLDUMP);
+	}
+
+	if (current_download_mode != QCOM_DOWNLOAD_NODUMP)
+		reboot_mode = REBOOT_WARM;
+
+	return NOTIFY_OK;
+}
+
+
+static int qcom_dload_probe(struct platform_device *pdev)
+{
+	struct qcom_dload *poweroff;
+
+	poweroff = devm_kzalloc(&pdev->dev, sizeof(*poweroff), GFP_KERNEL);
+	if (!poweroff)
+		return -ENOMEM;
+
+	if (enable_dump)
+		set_download_mode(QCOM_DOWNLOAD_FULLDUMP);
+	else {
+		set_download_mode(QCOM_DOWNLOAD_NODUMP);
+		qcom_scm_disable_sdi();
+	}
+
+	poweroff->panic_nb.notifier_call = qcom_dload_panic;
+	poweroff->panic_nb.priority = INT_MAX;
+	atomic_notifier_chain_register(&panic_notifier_list,
+				       &poweroff->panic_nb);
+
+	poweroff->reboot_nb.notifier_call = qcom_dload_reboot;
+	poweroff->reboot_nb.priority = 255;
+	register_reboot_notifier(&poweroff->reboot_nb);
+
+	platform_set_drvdata(pdev, poweroff);
+
+	return 0;
+}
+
+static int qcom_dload_remove(struct platform_device *pdev)
+{
+	struct qcom_dload *poweroff = platform_get_drvdata(pdev);
+
+	atomic_notifier_chain_unregister(&panic_notifier_list,
+					 &poweroff->panic_nb);
+	unregister_reboot_notifier(&poweroff->reboot_nb);
+
+	return 0;
+}
+
+static const struct of_device_id of_qcom_dload_match[] = {
+	{ .compatible = "qcom,dload-mode", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_qcom_dload_match);
+
+static struct platform_driver qcom_dload_driver = {
+	.probe = qcom_dload_probe,
+	.remove = qcom_dload_remove,
+	.driver = {
+		.name = "qcom-dload-mode",
+		.of_match_table = of_match_ptr(of_qcom_dload_match),
+	},
+};
+
+static int __init qcom_dload_driver_init(void)
+{
+	return platform_driver_register(&qcom_dload_driver);
+}
+#if IS_MODULE(CONFIG_POWER_RESET_QCOM_DOWNLOAD_MODE)
+module_init(qcom_dload_driver_init);
+#else
+pure_initcall(qcom_dload_driver_init);
+#endif
+
+static void __exit qcom_dload_driver_exit(void)
+{
+	return platform_driver_unregister(&qcom_dload_driver);
+}
+module_exit(qcom_dload_driver_exit);
+
+MODULE_DESCRIPTION("MSM Download Mode Driver");
+MODULE_LICENSE("GPL v2");