In order to aid post-mortem debugging the Qualcomm platforms provides 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 somehwere 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.
Signed-off-by: Bjorn Andersson
---
Changes since v2:
- Define memory address by reference to TCSR
- Provide Kconfig option for defaulting to enabled
- Provided some comment in the code
Changes since v1:
- Specify DT propert being two-cell
- Correct handling of scm-call return code
.../devicetree/bindings/firmware/qcom,scm.txt | 2 +
drivers/firmware/Kconfig | 11
drivers/firmware/qcom_scm-32.c | 6 ++
drivers/firmware/qcom_scm-64.c | 13
drivers/firmware/qcom_scm.c| 69 ++
drivers/firmware/qcom_scm.h| 2 +
6 files changed, 103 insertions(+)
diff --git a/Documentation/devicetree/bindings/firmware/qcom,scm.txt
b/Documentation/devicetree/bindings/firmware/qcom,scm.txt
index 20f26fbce875..838dba841797 100644
--- a/Documentation/devicetree/bindings/firmware/qcom,scm.txt
+++ b/Documentation/devicetree/bindings/firmware/qcom,scm.txt
@@ -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 reference to the TCSR hardware block containing the
+ download mode control register (optional)
Example for MSM8916:
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 6e4ed5a9c6fd..ed23c77d6361 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -215,6 +215,17 @@ config QCOM_SCM_64
def_bool y
depends on QCOM_SCM && ARM64
+config QCOM_SCM_DOWNLOAD_MODE_DEFAULT
+ bool "Qualcomm Download mode enabled by default"
+ depends on QCOM_SCM
+ 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 TI_SCI_PROTOCOL
tristate "TI System Control Interface (TISCI) Message Protocol"
depends on TI_MESSAGE_MANAGER
diff --git a/drivers/firmware/qcom_scm-32.c b/drivers/firmware/qcom_scm-32.c
index 11fdb1584823..68b2033bc30e 100644
--- a/drivers/firmware/qcom_scm-32.c
+++ b/drivers/firmware/qcom_scm-32.c
@@ -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 {
diff --git a/drivers/firmware/qcom_scm-64.c b/drivers/firmware/qcom_scm-64.c
index bf50fb59852e..3fea6f563ca9 100644
--- a/drivers/firmware/qcom_scm-64.c
+++ b/drivers/firmware/qcom_scm-64.c
@@ -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)
{
diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index e18d63935648..88472cde8936 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -19,15 +19,20 @@
#include
#include
#include
+#include
#include
#include
#include
+#include
#include
#include
#include
#include "qcom_scm.h"
+static bool download_mode = IS_ENABLED(CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT);
+module_param(download_mode, bool, 0);
+
#define SCM_HAS_CORE_C
