mmc-utils: Add CMD0 softreset and preidle command

CMD0 may be used to see if the hardware can handle a UHS card
that completed the voltage switch. If a UHS card has problems
coming back up after CMD0 your hardware may not support a hard
reset properly.

Signed-off-by: Christian Loehle <cloehle@hyperstone.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Link: https://lore.kernel.org/r/0657285aa7c64cbe89f9275fd5598345@hyperstone.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

mmc.c

@@ -245,6 +245,16 @@ static struct Command commands[] = {
 		"be 1.",
 	NULL
 	},
+	{ do_softreset, -1,
+	  "softreset", "<device>\n"
+	  "Issues a CMD0 softreset, e.g. for testing if hardware reset for UHS works",
+	  NULL
+	},
+	{ do_preidle, -1,
+	  "preidle", "<device>\n"
+	  "Issues a CMD0 GO_PRE_IDLE",
+	  NULL
+	},
 	{ 0, 0, 0, 0 }
 };
 

mmc.h

@@ -21,6 +21,9 @@
 #include <linux/mmc/ioctl.h>
 
 /* From kernel linux/mmc/mmc.h */
+#define MMC_GO_IDLE_STATE         0   /* bc                          */
+#define MMC_GO_IDLE_STATE_ARG		0x0
+#define MMC_GO_PRE_IDLE_STATE_ARG	0xF0F0F0F0
 #define MMC_SWITCH		6	/* ac	[31:0] See below	R1b */
 #define MMC_SEND_EXT_CSD	8	/* adtc				R1  */
 #define MMC_SEND_STATUS		13	/* ac   [31:16] RCA        R1  */
@@ -226,6 +229,7 @@
 
 
 /* From kernel linux/mmc/core.h */
+#define MMC_RSP_NONE	0			/* no response */
 #define MMC_RSP_PRESENT	(1 << 0)
 #define MMC_RSP_136	(1 << 1)		/* 136 bit response */
 #define MMC_RSP_CRC	(1 << 2)		/* expect valid crc */
@@ -234,6 +238,7 @@
 
 #define MMC_CMD_AC	(0 << 5)
 #define MMC_CMD_ADTC	(1 << 5)
+#define MMC_CMD_BC	(2 << 5)
 
 #define MMC_RSP_SPI_S1	(1 << 7)		/* one status byte */
 #define MMC_RSP_SPI_BUSY (1 << 10)		/* card may send busy */

mmc_cmds.c

@@ -3050,3 +3050,54 @@ out:
 	close(dev_fd);
 	return ret;
 }
+
+static void issue_cmd0(char *device, __u32 arg)
+{
+	struct mmc_ioc_cmd idata;
+	int fd;
+
+	fd = open(device, O_RDWR);
+	if (fd < 0) {
+		perror("open");
+		exit(1);
+	}
+
+	memset(&idata, 0, sizeof(idata));
+	idata.opcode = MMC_GO_IDLE_STATE;
+	idata.arg = arg;
+	idata.flags = MMC_RSP_NONE | MMC_CMD_BC;
+
+	/* No need to check for error, it is expected */
+	ioctl(fd, MMC_IOC_CMD, &idata);
+	close(fd);
+}
+
+int do_softreset(int nargs, char **argv)
+{
+	char *device;
+
+	if (nargs != 2) {
+		fprintf(stderr, "Usage: mmc softreset </path/to/mmcblkX>\n");
+		exit(1);
+	}
+
+	device = argv[1];
+	issue_cmd0(device, MMC_GO_IDLE_STATE_ARG);
+
+	return 0;
+}
+
+int do_preidle(int nargs, char **argv)
+{
+	char *device;
+
+	if (nargs != 2) {
+		fprintf(stderr, "Usage: mmc preidle </path/to/mmcblkX>\n");
+		exit(1);
+	}
+
+	device = argv[1];
+	issue_cmd0(device, MMC_GO_PRE_IDLE_STATE_ARG);
+
+	return 0;
+}

mmc_cmds.h

@@ -47,3 +47,5 @@ int do_read_cid(int argc, char **argv);
 int do_read_csd(int argc, char **argv);
 int do_erase(int nargs, char **argv);
 int do_general_cmd_read(int nargs, char **argv);
+int do_softreset(int nargs, char **argv);
+int do_preidle(int nargs, char **argv);