[1/3] soc: qcom: Add download mode support

diff --git a/MAINTAINERS b/MAINTAINERS
index a61f4f3b78a9..e51226f11bce 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15327,6 +15327,13 @@  L:	linux-arm-msm@vger.kernel.org
 S:	Maintained
 F:	drivers/crypto/qce/
 
+QUALCOMM DOWNLOAD MODE DRIVER
+M:	Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
+L:	linux-arm-msm@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/arm/msm/qcom,dload-mode.yaml
+F:	drivers/soc/qcom/download_mode.c
+
 QUALCOMM EMAC GIGABIT ETHERNET DRIVER
 M:	Timur Tabi <timur@kernel.org>
 L:	netdev@vger.kernel.org
diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
index 79b568f82a1c..dc41fcfc4ac8 100644
--- a/drivers/soc/qcom/Kconfig
+++ b/drivers/soc/qcom/Kconfig
@@ -42,6 +42,16 @@  config QCOM_CPR
 	  To compile this driver as a module, choose M here: the module will
 	  be called qcom-cpr
 
+config QCOM_DLOAD_MODE
+	tristate "QCOM Download Mode support"
+	depends on ARCH_QCOM || COMPILE_TEST
+	help
+	  Say Y here to enable support for download mode on QTI platforms.
+
+	  Download mode driver configures the download mode cookies and SDI
+	  (System Debug Image) required to collect ramdump for post-mortem
+	  debug on Qualcomm Technologies, Inc. platforms.
+
 config QCOM_GENI_SE
 	tristate "QCOM GENI Serial Engine Driver"
 	depends on ARCH_QCOM || COMPILE_TEST
diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
index ad675a6593d0..674520c9828e 100644
--- a/drivers/soc/qcom/Makefile
+++ b/drivers/soc/qcom/Makefile
@@ -4,6 +4,7 @@  obj-$(CONFIG_QCOM_AOSS_QMP) +=	qcom_aoss.o
 obj-$(CONFIG_QCOM_GENI_SE) +=	qcom-geni-se.o
 obj-$(CONFIG_QCOM_COMMAND_DB) += cmd-db.o
 obj-$(CONFIG_QCOM_CPR)		+= cpr.o
+obj-$(CONFIG_QCOM_DLOAD_MODE)	+= download_mode.o
 obj-$(CONFIG_QCOM_GSBI)	+=	qcom_gsbi.o
 obj-$(CONFIG_QCOM_MDT_LOADER)	+= mdt_loader.o
 obj-$(CONFIG_QCOM_OCMEM)	+= ocmem.o
diff --git a/drivers/soc/qcom/download_mode.c b/drivers/soc/qcom/download_mode.c
new file mode 100644
index 000000000000..519fdbe8669b
--- /dev/null
+++ b/drivers/soc/qcom/download_mode.c
@@ -0,0 +1,152 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2021, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/of_address.h>
+#include <linux/panic_notifier.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+
+#define DLOAD_MODE_COOKIE1	0xe47b337d
+#define DLOAD_MODE_COOKIE2	0xce14091a
+
+struct qcom_dload_mode {
+	void __iomem *dload_mode;
+	void __iomem *sdi_disable;
+	bool in_panic;
+};
+
+static struct qcom_dload_mode *dmode;
+
+static int dload_mode_reboot_notifier(struct notifier_block *self,
+			       unsigned long v, void *p)
+{
+	/*
+	 * Don't enter download mode for normal reboot, so clear the
+	 * download mode cookie and disable SDI.
+	 */
+	if (!dmode->in_panic) {
+		writel(0, dmode->dload_mode);
+		writel(1, dmode->sdi_disable);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int dload_mode_panic_notifier(struct notifier_block *self,
+			       unsigned long v, void *p)
+{
+	dmode->in_panic = true;
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block dload_mode_reboot_nb = {
+	.notifier_call = dload_mode_reboot_notifier,
+};
+
+static struct notifier_block dload_mode_panic_nb = {
+	.notifier_call = dload_mode_panic_notifier,
+};
+
+static void qcom_unset_dload_mode(void)
+{
+	writel(0, dmode->dload_mode);
+	writel(0, dmode->dload_mode + sizeof(u32));
+}
+
+static void qcom_set_dload_mode(void)
+{
+	writel(DLOAD_MODE_COOKIE1, dmode->dload_mode);
+	writel(DLOAD_MODE_COOKIE2, dmode->dload_mode + sizeof(u32));
+}
+
+static int __init qcom_dload_mode_init(void)
+{
+	struct resource imem, sdi_base;
+	struct of_phandle_args args;
+	struct device_node *np;
+	int ret;
+
+	dmode = kzalloc(sizeof(*dmode), GFP_KERNEL);
+	if (!dmode)
+		return -ENOMEM;
+
+	np = of_find_compatible_node(NULL, NULL, "qcom,dload-mode");
+	if (!np)
+		return -ENOENT;
+
+	ret = of_address_to_resource(np, 0, &imem);
+	if (ret < 0)
+		return ret;
+
+	ret = of_parse_phandle_with_fixed_args(np,
+					       "qcom,sdi-disable-regs",
+					       2, 0, &args);
+	of_node_put(np);
+	if (ret < 0) {
+		pr_err("Failed to parse sdi-disable-regs\n");
+		return -EINVAL;
+	}
+
+	ret = of_address_to_resource(args.np, 0, &sdi_base);
+	of_node_put(args.np);
+	if (ret < 0)
+		return ret;
+
+	dmode->dload_mode = ioremap(imem.start, resource_size(&imem));
+	if (!dmode->dload_mode) {
+		pr_err("Failed to map download mode region\n");
+		return -ENOMEM;
+	}
+
+	dmode->sdi_disable = ioremap(sdi_base.start + args.args[0], args.args[1]);
+	if (!dmode->sdi_disable) {
+		pr_err("Failed to map sdi disable region\n");
+		return -ENOMEM;
+	}
+
+	ret = atomic_notifier_chain_register(&panic_notifier_list,
+					     &dload_mode_panic_nb);
+	if (ret) {
+		pr_err("Failed to register panic notifier: %d\n", ret);
+		return ret;
+	}
+
+	ret = register_reboot_notifier(&dload_mode_reboot_nb);
+	if (ret) {
+		pr_err("Failed to register reboot notifier: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Set the download mode cookies here so that after this point on
+	 * any crash handled either by kernel or other crashes such as
+	 * watchdog bite handled by other entities like secure world,
+	 * download mode is entered.
+	 */
+	qcom_set_dload_mode();
+
+	return 0;
+}
+device_initcall(qcom_dload_mode_init);
+
+static void __exit qcom_dload_mode_exit(void)
+{
+	qcom_unset_dload_mode();
+	unregister_reboot_notifier(&dload_mode_reboot_nb);
+	atomic_notifier_chain_unregister(&panic_notifier_list,
+					 &dload_mode_panic_nb);
+	iounmap(dmode->sdi_disable);
+	iounmap(dmode->dload_mode);
+	kfree(dmode);
+	dmode = NULL;
+}
+module_exit(qcom_dload_mode_exit);
+
+MODULE_DESCRIPTION("Qualcomm Technologies, Inc. Download Mode driver");
+MODULE_LICENSE("GPL v2");