firmware: qcom: scm: Refactor code to support multiple dload mode

Currently on Qualcomm SoC, download_mode is enabled if
CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT is selected or
passed a boolean value from command line.

Refactor the code such that it supports multiple download
modes and drop CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT config
instead, give interface to set the download mode from
module parameter while being backword compatible at the
same time.

Signed-off-by: Mukesh Ojha <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bjorn Andersson <[e-mail]>

drivers/firmware/qcom/Kconfig

···
 
 endchoice
 
-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 QCOM_QSEECOM
 	bool "Qualcomm QSEECOM interface driver"
 	depends on QCOM_SCM=y

drivers/firmware/qcom/qcom_scm.c

···
 #include <linux/init.h>
 #include <linux/interconnect.h>
 #include <linux/interrupt.h>
+#include <linux/kstrtox.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
···
 #include "qcom_scm.h"
 #include "qcom_tzmem.h"
 
-static bool download_mode = IS_ENABLED(CONFIG_QCOM_SCM_DOWNLOAD_MODE_DEFAULT);
-module_param(download_mode, bool, 0);
+static u32 download_mode;
 
 struct qcom_scm {
 	struct device *dev;
···
 	[SMC_CONVENTION_ARM_32] = "smc arm 32",
 	[SMC_CONVENTION_ARM_64] = "smc arm 64",
 	[SMC_CONVENTION_LEGACY] = "smc legacy",
+};
+
+static const char * const download_mode_name[] = {
+	[QCOM_DLOAD_NODUMP]	= "off",
+	[QCOM_DLOAD_FULLDUMP]	= "full",
 };
 
 static struct qcom_scm *__scm;
···
 	return qcom_scm_io_writel(addr, new);
 }
 
-static void qcom_scm_set_download_mode(bool enable)
+static void qcom_scm_set_download_mode(u32 dload_mode)
 {
-	u32 val = enable ? QCOM_DLOAD_FULLDUMP : QCOM_DLOAD_NODUMP;
 	int ret = 0;
 
 	if (__scm->dload_mode_addr) {
 		ret = qcom_scm_io_rmw(__scm->dload_mode_addr, QCOM_DLOAD_MASK,
-				      FIELD_PREP(QCOM_DLOAD_MASK, val));
+				      FIELD_PREP(QCOM_DLOAD_MASK, dload_mode));
 	} else if (__qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_BOOT,
 						QCOM_SCM_BOOT_SET_DLOAD_MODE)) {
-		ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
+		ret = __qcom_scm_set_dload_mode(__scm->dev, !!dload_mode);
 	} else {
 		dev_err(__scm->dev,
 			"No available mechanism for setting download mode\n");
···
 	return IRQ_HANDLED;
 }
 
+static int get_download_mode(char *buffer, const struct kernel_param *kp)
+{
+	if (download_mode >= ARRAY_SIZE(download_mode_name))
+		return sysfs_emit(buffer, "unknown mode\n");
+
+	return sysfs_emit(buffer, "%s\n", download_mode_name[download_mode]);
+}
+
+static int set_download_mode(const char *val, const struct kernel_param *kp)
+{
+	bool tmp;
+	int ret;
+
+	ret = sysfs_match_string(download_mode_name, val);
+	if (ret < 0) {
+		ret = kstrtobool(val, &tmp);
+		if (ret < 0) {
+			pr_err("qcom_scm: err: %d\n", ret);
+			return ret;
+		}
+
+		ret = tmp ? 1 : 0;
+	}
+
+	download_mode = ret;
+	if (__scm)
+		qcom_scm_set_download_mode(download_mode);
+
+	return 0;
+}
+
+static const struct kernel_param_ops download_mode_param_ops = {
+	.get = get_download_mode,
+	.set = set_download_mode,
+};
+
+module_param_cb(download_mode, &download_mode_param_ops, NULL, 0644);
+MODULE_PARM_DESC(download_mode,
+		"download mode: off/0/N for no dump mode, full/on/1/Y for full dump mode");
+
 static int qcom_scm_probe(struct platform_device *pdev)
 {
 	struct qcom_tzmem_pool_config pool_config;
···
 	__get_convention();
 
 	/*
-	 * If requested enable "download mode", from this point on warmboot
+	 * If "download mode" is requested, from this point on warmboot
 	 * will cause the boot stages to enter download mode, unless
 	 * disabled below by a clean shutdown/reboot.
 	 */
···
 static void qcom_scm_shutdown(struct platform_device *pdev)
 {
 	/* Clean shutdown, disable download mode to allow normal restart */
-	qcom_scm_set_download_mode(false);
+	qcom_scm_set_download_mode(QCOM_DLOAD_NODUMP);
 }
 
 static const struct of_device_id qcom_scm_dt_match[] = {