[PATCH] power: reset: msm: Add support for download-mode control

[Rajendra Nayak]

commit '8c1b7dc9b: firmware: qcom: scm: Expose download-mode control'
added support for download-mode control using the scm firmware
driver for platforms which require a secure call to write the magic
cookie into the tcsr location.

For platforms which *do not* need an scm call and where the kernel can
write the cookie by a direct read/write, add similar support in the
msm-poweroff driver.
Similar to the scm driver, the msm-poweroff driver clears the cookie
during a clean reboot.

Download mode using msm-poweroff driver can be enabled by including
msm-poweroff.download_mode=1 on the command line.

Signed-off-by: Rajendra Nayak <rnayak@xxxxxxxxxxxxxx>
---
 .../bindings/power/reset/msm-poweroff.txt          |  3 ++
 drivers/power/reset/Kconfig                        | 11 +++++++
 drivers/power/reset/msm-poweroff.c                 | 38 ++++++++++++++++++++++
 3 files changed, 52 insertions(+)

diff --git a/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt b/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt
index ce44ad3..9dd489f 100644
--- a/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt
+++ b/Documentation/devicetree/bindings/power/reset/msm-poweroff.txt
@@ -8,6 +8,9 @@ settings.
 Required Properties:
 -compatible: "qcom,pshold"
 -reg: Specifies the physical address of the ps-hold register
+Optional Properties:
+-qcom,dload-mode: phandle to the TCSR hardware block and offset of the
+		 download mode control register
 
 Example:
 
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index df58fc8..0c97e34 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -104,6 +104,17 @@ config POWER_RESET_MSM
 	help
 	  Power off and restart support for Qualcomm boards.
 
+config POWER_RESET_MSM_DOWNLOAD_MODE
+	bool "Qualcomm download mode enabled by default"
+	depends on POWER_RESET_MSM
+	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 POWER_RESET_OCELOT_RESET
 	bool "Microsemi Ocelot reset driver"
 	depends on MSCC_OCELOT || COMPILE_TEST
diff --git a/drivers/power/reset/msm-poweroff.c b/drivers/power/reset/msm-poweroff.c
index 01b8c71..c33eac5 100644
--- a/drivers/power/reset/msm-poweroff.c
+++ b/drivers/power/reset/msm-poweroff.c
@@ -18,11 +18,20 @@
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/reboot.h>
+#include <linux/regmap.h>
 #include <linux/pm.h>
 
+static bool download_mode = IS_ENABLED(CONFIG_POWER_RESET_MSM_DOWNLOAD_MODE);
+module_param(download_mode, bool, 0);
+
+#define QCOM_SET_DLOAD_MODE 0x10
 static void __iomem *msm_ps_hold;
+static struct regmap *tcsr_regmap;
+static unsigned int dload_mode_offset;
+
 static int deassert_pshold(struct notifier_block *nb, unsigned long action,
 			   void *data)
 {
@@ -44,9 +53,30 @@ static void do_msm_poweroff(void)
 
 static int msm_restart_probe(struct platform_device *pdev)
 {
+	int ret;
+	struct of_phandle_args args;
 	struct device *dev = &pdev->dev;
 	struct resource *mem;
 
+	if (download_mode) {
+		ret = of_parse_phandle_with_fixed_args(dev->of_node,
+						       "qcom,dload-mode", 1, 0,
+						       &args);
+		if (ret < 0)
+			return ret;
+
+		tcsr_regmap = syscon_node_to_regmap(args.np);
+		of_node_put(args.np);
+		if (IS_ERR(tcsr_regmap))
+			return PTR_ERR(tcsr_regmap);
+
+		dload_mode_offset = args.args[0];
+
+		/* Enable download mode by writing the cookie */
+		regmap_write(tcsr_regmap, dload_mode_offset,
+			     QCOM_SET_DLOAD_MODE);
+	}
+
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	msm_ps_hold = devm_ioremap_resource(dev, mem);
 	if (IS_ERR(msm_ps_hold))
@@ -59,6 +89,13 @@ static int msm_restart_probe(struct platform_device *pdev)
 	return 0;
 }
 
+static void msm_restart_shutdown(struct platform_device *pdev)
+{
+	/* Clean shutdown, disable download mode to allow normal restart */
+	if (download_mode)
+		regmap_write(tcsr_regmap, dload_mode_offset, 0x0);
+}
+
 static const struct of_device_id of_msm_restart_match[] = {
 	{ .compatible = "qcom,pshold", },
 	{},
@@ -71,6 +108,7 @@ static int msm_restart_probe(struct platform_device *pdev)
 		.name = "msm-restart",
 		.of_match_table = of_match_ptr(of_msm_restart_match),
 	},
+	.shutdown = msm_restart_shutdown,
 };
 
 static int __init msm_restart_init(void)
-- 
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