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Commit 8c1b7dc9 authored by Bjorn Andersson's avatar Bjorn Andersson Committed by Andy Gross
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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 <sboyd@codeaurora.org>
Signed-off-by: default avatarBjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: default avatarAndy Gross <andy.gross@linaro.org>
parent 4e659dbe

Documentation/devicetree/bindings/firmware/qcom,scm.txt

+2 −0
Original line number Diff line number Diff line
@@ -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:

drivers/firmware/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -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

drivers/firmware/qcom_scm-32.c

+6 −0
Original line number Diff line number Diff line
@@ -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 {

drivers/firmware/qcom_scm-64.c

+13 −0
Original line number Diff line number Diff line
@@ -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)

{

drivers/firmware/qcom_scm.c

+75 −0
Original line number Diff line number Diff line
@@ -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)