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@xxxxxxxxxxxxxx>
---
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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