Commit 8c1b7dc9 authored by Bjorn Andersson's avatar Bjorn Andersson Committed by Andy Gross

firmware: qcom: scm: Expose download-mode control

In order to aid post-mortem debugging the Qualcomm platforms provide a
"memory download mode", where the boot loader will provide an interface
for custom tools to "download" the content of RAM to a host machine.

The mode is triggered by writing a magic value somewhere in RAM, that is
read in the boot code path after a warm-restart. Two mechanism for
setting this magic value are supported in modern platforms; a direct SCM
call to enable the mode or through a secure io write of a magic value.

In order for a normal reboot not to trigger "download mode" the magic
must be cleared during a clean reboot.

Download mode has to be enabled by including qcom_scm.download_mode=1 on
the command line.
Reviewed-by: default avatarStephen Boyd <>
Signed-off-by: default avatarBjorn Andersson <>
Signed-off-by: default avatarAndy Gross <>
parent 4e659dbe
......@@ -18,6 +18,8 @@ Required properties:
* Core, iface, and bus clocks required for "qcom,scm"
- clock-names: Must contain "core" for the core clock, "iface" for the interface
clock and "bus" for the bus clock per the requirements of the compatible.
- qcom,dload-mode: phandle to the TCSR hardware block and offset of the
download mode control register (optional)
Example for MSM8916:
......@@ -215,6 +215,17 @@ config QCOM_SCM_64
def_bool y
depends on QCOM_SCM && ARM64
bool "Qualcomm download mode enabled by default"
depends on QCOM_SCM
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.
tristate "TI System Control Interface (TISCI) Message Protocol"
......@@ -561,6 +561,12 @@ int __qcom_scm_pas_mss_reset(struct device *dev, bool reset)
return ret ? : le32_to_cpu(out);
int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
return qcom_scm_call_atomic2(QCOM_SCM_SVC_BOOT, QCOM_SCM_SET_DLOAD_MODE,
enable ? QCOM_SCM_SET_DLOAD_MODE : 0, 0);
int __qcom_scm_set_remote_state(struct device *dev, u32 state, u32 id)
struct {
......@@ -440,6 +440,19 @@ int __qcom_scm_iommu_secure_ptbl_init(struct device *dev, u64 addr, u32 size,
return ret;
int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
struct qcom_scm_desc desc = {0};
struct arm_smccc_res res;
desc.args[0] = QCOM_SCM_SET_DLOAD_MODE;
desc.args[1] = enable ? QCOM_SCM_SET_DLOAD_MODE : 0;
desc.arginfo = QCOM_SCM_ARGS(2);
return qcom_scm_call(dev, QCOM_SCM_SVC_BOOT, QCOM_SCM_SET_DLOAD_MODE,
&desc, &res);
int __qcom_scm_io_readl(struct device *dev, phys_addr_t addr,
unsigned int *val)
......@@ -19,15 +19,20 @@
#include <linux/cpumask.h>
#include <linux/export.h>
#include <linux/dma-mapping.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/qcom_scm.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_platform.h>
#include <linux/clk.h>
#include <linux/reset-controller.h>
#include "qcom_scm.h"
module_param(download_mode, bool, 0);
#define SCM_HAS_BUS_CLK BIT(2)
......@@ -38,6 +43,8 @@ struct qcom_scm {
struct clk *iface_clk;
struct clk *bus_clk;
struct reset_controller_dev reset;
u64 dload_mode_addr;
static struct qcom_scm *__scm;
......@@ -345,6 +352,54 @@ int qcom_scm_io_writel(phys_addr_t addr, unsigned int val)
static void qcom_scm_set_download_mode(bool enable)
bool avail;
int ret = 0;
avail = __qcom_scm_is_call_available(__scm->dev,
if (avail) {
ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
} else if (__scm->dload_mode_addr) {
ret = __qcom_scm_io_writel(__scm->dev, __scm->dload_mode_addr,
enable ? QCOM_SCM_SET_DLOAD_MODE : 0);
} else {
"No available mechanism for setting download mode\n");
if (ret)
dev_err(__scm->dev, "failed to set download mode: %d\n", ret);
static int qcom_scm_find_dload_address(struct device *dev, u64 *addr)
struct device_node *tcsr;
struct device_node *np = dev->of_node;
struct resource res;
u32 offset;
int ret;
tcsr = of_parse_phandle(np, "qcom,dload-mode", 0);
if (!tcsr)
return 0;
ret = of_address_to_resource(tcsr, 0, &res);
if (ret)
return ret;
ret = of_property_read_u32_index(np, "qcom,dload-mode", 1, &offset);
if (ret < 0)
return ret;
*addr = res.start + offset;
return 0;
* qcom_scm_is_available() - Checks if SCM is available
......@@ -370,6 +425,10 @@ static int qcom_scm_probe(struct platform_device *pdev)
if (!scm)
return -ENOMEM;
ret = qcom_scm_find_dload_address(&pdev->dev, &scm->dload_mode_addr);
if (ret < 0)
return ret;
clks = (unsigned long)of_device_get_match_data(&pdev->dev);
if (clks & SCM_HAS_CORE_CLK) {
scm->core_clk = devm_clk_get(&pdev->dev, "core");
......@@ -418,9 +477,24 @@ static int qcom_scm_probe(struct platform_device *pdev)
* If requested enable "download mode", from this point on warmboot
* will cause the the boot stages to enter download mode, unless
* disabled below by a clean shutdown/reboot.
if (download_mode)
return 0;
static void qcom_scm_shutdown(struct platform_device *pdev)
/* Clean shutdown, disable download mode to allow normal restart */
if (download_mode)
static const struct of_device_id qcom_scm_dt_match[] = {
{ .compatible = "qcom,scm-apq8064",
/* FIXME: This should have .data = (void *) SCM_HAS_CORE_CLK */
......@@ -448,6 +522,7 @@ static struct platform_driver qcom_scm_driver = {
.of_match_table = qcom_scm_dt_match,
.probe = qcom_scm_probe,
.shutdown = qcom_scm_shutdown,
static int __init qcom_scm_init(void)
......@@ -14,9 +14,11 @@
#define QCOM_SCM_SVC_BOOT 0x1
#define QCOM_SCM_BOOT_ADDR 0x1
#define QCOM_SCM_BOOT_ADDR_MC 0x11
extern int __qcom_scm_set_remote_state(struct device *dev, u32 state, u32 id);
extern int __qcom_scm_set_dload_mode(struct device *dev, bool enable);
#define QCOM_SCM_FLAG_HLOS 0x01
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