[PATCH] mmc-utils: Add softreset command for issuing CMD0

[Christian Loehle <CLoehle@hyperstone.com>]

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>
---
 mmc.c      |  5 +++++
 mmc.h      |  3 +++
 mmc_cmds.c | 30 ++++++++++++++++++++++++++++++
 mmc_cmds.h |  1 +
 4 files changed, 39 insertions(+)

diff --git a/mmc.c b/mmc.c
index 6c56387..ba2c883 100644
--- a/mmc.c
+++ b/mmc.c
@@ -245,6 +245,11 @@ static struct Command commands[] = {
 		"be 1.",
 	NULL
 	},
+	{ do_soft_reset, -1,
+	  "softreset", "<device>\n"
+	  "Issues a CMD0 softreset, e.g. for testing if hardware reset for UHS works\n\n",
+	  NULL
+	},
 	{ 0, 0, 0, 0 }
 };
 
diff --git a/mmc.h b/mmc.h
index daff62c..9796d2e 100644
--- a/mmc.h
+++ b/mmc.h
@@ -21,6 +21,7 @@
 #include <linux/mmc/ioctl.h>
 
 /* From kernel linux/mmc/mmc.h */
+#define MMC_GO_IDLE_STATE         0   /* bc                          */
 #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 +227,7 @@
 
 
 /* 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 +236,7 @@
 
 #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 */
diff --git a/mmc_cmds.c b/mmc_cmds.c
index 12b7802..c027cfa 100644
--- a/mmc_cmds.c
+++ b/mmc_cmds.c
@@ -3039,3 +3039,33 @@ out:
 	close(dev_fd);
 	return ret;
 }
+
+int do_soft_reset(int nargs, char **argv)
+{
+	int fd;
+	char *device;
+	struct mmc_ioc_cmd idata;
+
+	if (nargs != 2) {
+		fprintf(stderr, "Usage: mmc status softreset </path/to/mmcblkX>\n");
+		exit(1);
+	}
+
+	device = argv[1];
+
+	fd = open(device, O_RDWR);
+	if (fd < 0) {
+		perror("open");
+		exit(1);
+	}
+
+	memset(&idata, 0, sizeof(idata));
+	idata.opcode = MMC_GO_IDLE_STATE;
+	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);
+
+	return 0;
+}
diff --git a/mmc_cmds.h b/mmc_cmds.h
index 0f7c004..c112a95 100644
--- a/mmc_cmds.h
+++ b/mmc_cmds.h
@@ -47,3 +47,4 @@ 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_soft_reset(int nargs, char **argv);
-- 
2.36.1

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