Samsung Android Modem Device Driver -mss Ver.3-

On Samsung devices with MSS Ver.3, trigger a RAM dump via:

echo 1 > /sys/devices/platform/modem/dump

Or via secret code *#9900# → “Copy Dump for Log” → choose “Modem Dump”.

The dump is stored as ramdump_modem_... and requires Samsung’s proprietary modem_parser tool to analyze.

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MSS v3 supports automatic power collapse when the modem is idle:

Because the modem driver sits between Android’s userspace and sensitive hardware, bugs can manifest as signal loss, overheating, or “No SIM card” errors. Below are real-world scenarios and debugging approaches. samsung android modem device driver -mss ver.3-

Typical device tree node for MSS v3 on an Exynos 2200 device:

mss: mss@0x40000000 
    compatible = "samsung,exynos-mss-v3";
    reg = <0x40000000 0x2000000>,   /* CP shared memory */
          <0x10860000 0x1000>;      /* MSS control registers */
    interrupts = <GIC_SPI 456 IRQ_TYPE_LEVEL_HIGH>;
    mbox-names = "mss0", "mss1";
    mboxes = <&mss_mbox 0>, <&mss_mbox 1>;
    power-domains = <&pd_cp>;
    firmware-name = "mss_fw.bin";
    samsung,shmem-size = <0x800000>;
;

// samsung_mss_v3_diag.c
// Mock interface for MSS v3 modem diagnostics (Linux TTY/IPC)
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <sys/ioctl.h>
#define MSS_DEVICE "/dev/mss_v3_modem"
#define MSS_IOCTL_GET_VERSION  _IOR('M', 1, int)
#define MSS_IOCTL_SEND_URC     _IOW('M', 2, char*)
#define MSS_IOCTL_RESET        _IO('M', 3)
int mss_fd = -1;
int mss_open() 
mss_fd = open(MSS_DEVICE, O_RDWR 
void mss_get_version() 
int version;
if (ioctl(mss_fd, MSS_IOCTL_GET_VERSION, &version) == 0) 
printf("MSS version 3.x — sub-version: %d\n", version);
 else 
perror("Version query failed");

void mss_send_command(const char *cmd) 
if (write(mss_fd, cmd, strlen(cmd)) != (ssize_t)strlen(cmd)) 
perror("Write to modem failed");

void mss_read_response(char *buf, size_t len) 
ssize_t n = read(mss_fd, buf, len - 1);
if (n > 0) 
buf[n] = '\0';
printf("Modem MSS v3 reply: %s\n", buf);
 On Samsung devices with MSS Ver
int main() {
if (mss_open() < 0) return 1;
mss_get_version();
mss_send_command("AT+CRESET\r\n");
mss_read_response((char[128]){}, 128);
close(mss_fd);
return 0;

}

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E IPC_RTR : mss_ver3_recv_data: invalid header
E MSS_V3  : tx timeout on channel 7

Analysis: Use samsung-ipc-log from LineageOS’s tools: Or via secret code *#9900# → “Copy Dump

adb shell "echo 0xFFFF > /sys/kernel/debug/sipc5/debug_mask"
adb shell cat /sys/kernel/debug/sipc5/stats

Modern smartphones require robust, power-efficient communication between the Android application processor (AP) and the baseband processor (BP). Samsung’s Modem SubSystem (MSS) driver, now in its third major version, serves as the critical interface for Exynos SoCs (e.g., Exynos 2100, 2200, 2400). MSS v3 replaces earlier versions with a unified driver supporting 5G NSA/SA, carrier aggregation, and advanced power management.

The driver operates in the Linux kernel (usually under drivers/soc/samsung/mss/) and provides: