ipq40xx: qcom_scm: Disable SDI at boot

See my upstream RFC of this:
https://lore.kernel.org/linux-arm-msm/20200721080054.2803881-1-computersforpeace@gmail.com/

This fixes warm boot (reboot) for Google WiFi devices using their
factory bootloader/firmware.

I may resend this upstream eventually.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>

target/linux/ipq40xx/patches-5.10/420-firmware-qcom-scm-disable-SDI.patch

@@ -0,0 +1,47 @@
+--- a/drivers/firmware/qcom_scm.c
++++ b/drivers/firmware/qcom_scm.c
+@@ -404,6 +404,20 @@ static int __qcom_scm_set_dload_mode(str
+ 	return qcom_scm_call_atomic(__scm->dev, &desc, NULL);
+ }
+
++static int __qcom_scm_disable_sdi(struct device *dev)
++{
++	struct qcom_scm_desc desc = {
++		.svc = QCOM_SCM_SVC_BOOT,
++		.cmd = QCOM_SCM_BOOT_CONFIG_SDI,
++		.arginfo = QCOM_SCM_ARGS(2),
++		.args[0] = 1  /* 1: disable watchdog debug */,
++		.args[1] = 0  /* 0: disable SDI */,
++		.owner = ARM_SMCCC_OWNER_SIP,
++	};
++
++	return qcom_scm_call(__scm->dev, &desc, NULL);
++}
++
+ static void qcom_scm_set_download_mode(bool enable)
+ {
+ 	bool avail;
+@@ -1256,6 +1270,13 @@ static int qcom_scm_probe(struct platfor
+ 	if (download_mode)
+ 		qcom_scm_set_download_mode(true);
+
++	/*
++	 * Factory firmware leaves SDI (a debug interface), which prevents
++	 * clean reboot.
++	 */
++	if (of_machine_is_compatible("google,wifi"))
++		__qcom_scm_disable_sdi(__scm->dev);
++
+ 	return 0;
+ }
+
+--- a/drivers/firmware/qcom_scm.h
++++ b/drivers/firmware/qcom_scm.h
+@@ -77,6 +77,7 @@ extern int scm_legacy_call(struct device
+ #define QCOM_SCM_SVC_BOOT		0x01
+ #define QCOM_SCM_BOOT_SET_ADDR		0x01
+ #define QCOM_SCM_BOOT_TERMINATE_PC	0x02
++#define QCOM_SCM_BOOT_CONFIG_SDI	0x09
+ #define QCOM_SCM_BOOT_SET_DLOAD_MODE	0x10
+ #define QCOM_SCM_BOOT_SET_REMOTE_STATE	0x0a
+ #define QCOM_SCM_FLUSH_FLAG_MASK	0x3