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firmware: qcom: scm: Expose download-mode control

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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: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>
This commit is contained in:
Bjorn Andersson 2017-08-14 15:46:18 -07:00 • committed by Andy Gross
parent 4e659dbe2d
commit 8c1b7dc9ba
6 changed files with 109 additions and 0 deletions
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75
drivers/firmware/qcom_scm.c
View file

@ -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"
static bool download_mode = IS_ENABLED(CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT);
module_param(download_mode, bool, 0);
#define SCM_HAS_CORE_CLK BIT(0)
#define SCM_HAS_IFACE_CLK BIT(1)
#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)
}
EXPORT_SYMBOL(qcom_scm_io_writel);
static void qcom_scm_set_download_mode(bool enable)
{
bool avail;
int ret = 0;
avail = __qcom_scm_is_call_available(__scm->dev,
QCOM_SCM_SVC_BOOT,
QCOM_SCM_SET_DLOAD_MODE);
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 {
dev_err(__scm->dev,
"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);
of_node_put(tcsr);
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)
__qcom_scm_init();
/*
* 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)
qcom_scm_set_download_mode(true);
return 0;
}
static void qcom_scm_shutdown(struct platform_device *pdev)
{
/* Clean shutdown, disable download mode to allow normal restart */
if (download_mode)
qcom_scm_set_download_mode(false);
}
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)