diff mbox series

cmd: mmc: Add mmc reg read command for reading card registers

Message ID 20200620123002.2816-1-marex@denx.de
State Accepted
Commit b5f403936d037e0bc08e78b8af64adf53da13b90
Headers show
Series cmd: mmc: Add mmc reg read command for reading card registers | expand

Commit Message

Marek Vasut June 20, 2020, 12:30 p.m. UTC 
Add extension to the 'mmc' command to read out the card registers.
Currently, only the eMMC OCR/CID/CSD/EXTCSD/RCA/DSR register are
supported. A register value can either be displayed or read into
an environment variable.

Signed-off-by: Marek Vasut <marex at denx.de>
---
 cmd/Kconfig |  8 +++++
 cmd/mmc.c   | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

Comments

Michael Trimarchi June 20, 2020, 12:35 p.m. UTC | #1 
Hi

On Sat, Jun 20, 2020 at 2:30 PM Marek Vasut <marex at denx.de> wrote:
>
> Add extension to the 'mmc' command to read out the card registers.
> Currently, only the eMMC OCR/CID/CSD/EXTCSD/RCA/DSR register are
> supported. A register value can either be displayed or read into
> an environment variable.
>
> Signed-off-by: Marek Vasut <marex at denx.de>
> ---
>  cmd/Kconfig |  8 +++++
>  cmd/mmc.c   | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 102 insertions(+)
>
> diff --git a/cmd/Kconfig b/cmd/Kconfig
> index 192b3b262f..a0cf03c911 100644
> --- a/cmd/Kconfig
> +++ b/cmd/Kconfig
> @@ -1104,6 +1104,14 @@ config CMD_BKOPS_ENABLE
>           on a eMMC device. The feature is optionally available on eMMC devices
>           conforming to standard >= 4.41.
>
> +config CMD_MMC_REG
> +       bool "Enable support for reading card registers in the mmc command"
> +       depends on CMD_MMC
> +       default y
> +       help
> +         Enable the commands for reading card registers. This is useful
> +         mostly for debugging or extracting details from the card.
> +
>  config CMD_MMC_RPMB
>         bool "Enable support for RPMB in the mmc command"
>         depends on SUPPORT_EMMC_RPMB
> diff --git a/cmd/mmc.c b/cmd/mmc.c
> index 1529a3e05d..55fbfe822e 100644
> --- a/cmd/mmc.c
> +++ b/cmd/mmc.c
> @@ -912,6 +912,93 @@ static int do_mmc_bkops_enable(struct cmd_tbl *cmdtp, int flag,
>  }
>  #endif
>
> +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> +static int do_mmc_reg(struct cmd_tbl *cmdtp, int flag,
> +                        int argc, char *const argv[])
> +{
> +       ALLOC_CACHE_ALIGN_BUFFER(u8, ext_csd, MMC_MAX_BLOCK_LEN);
> +       struct mmc *mmc;
> +       int i, ret;
> +       u32 off;
> +
> +       if (argc < 3 || argc > 5)
> +               return CMD_RET_USAGE;
> +
> +       mmc = find_mmc_device(curr_device);
> +       if (!mmc) {
> +               printf("no mmc device at slot %x\n", curr_device);
> +               return CMD_RET_FAILURE;
> +       }
> +
> +       if (IS_SD(mmc)) {
> +               printf("SD registers are not supported\n");
> +               return CMD_RET_FAILURE;
> +       } else {

else is not needed

> +               off = simple_strtoul(argv[3], NULL, 10);
> +               if (!strcmp(argv[2], "cid")) {
> +                       if (off > 1)
> +                               return CMD_RET_USAGE;
> +                       printf("CID[%i]: 0x%08x\n", off, mmc->cid[off]);
> +                       if (argv[4])
> +                               env_set_hex(argv[4], mmc->cid[off]);
> +                       return CMD_RET_SUCCESS;
> +               }
> +               if (!strcmp(argv[2], "csd")) {
> +                       if (off > 3)
> +                               return CMD_RET_USAGE;
> +                       printf("CSD[%i]: 0x%08x\n", off, mmc->csd[off]);
> +                       if (argv[4])
> +                               env_set_hex(argv[4], mmc->csd[off]);
> +                       return CMD_RET_SUCCESS;
> +               }
> +               if (!strcmp(argv[2], "dsr")) {
> +                       printf("DSR: 0x%08x\n", mmc->dsr);
> +                       if (argv[4])
> +                               env_set_hex(argv[4], mmc->dsr);
> +                       return CMD_RET_SUCCESS;
> +               }
> +               if (!strcmp(argv[2], "ocr")) {
> +                       printf("OCR: 0x%08x\n", mmc->ocr);
> +                       if (argv[4])
> +                               env_set_hex(argv[4], mmc->ocr);
> +                       return CMD_RET_SUCCESS;
> +               }
> +               if (!strcmp(argv[2], "rca")) {
> +                       printf("RCA: 0x%08x\n", mmc->rca);
> +                       if (argv[4])
> +                               env_set_hex(argv[4], mmc->rca);
> +                       return CMD_RET_SUCCESS;
> +               }
> +               if (!strcmp(argv[2], "extcsd") &&
> +                   mmc->version >= MMC_VERSION_4_41) {

Can you factorize all the conditions?
string, function

Even use strcmp("extcsd", arg

Michael

> +                       ret = mmc_send_ext_csd(mmc, ext_csd);
> +                       if (ret)
> +                               return ret;
> +                       if (!strcmp(argv[3], "all")) {
> +                               /* Dump the entire register */
> +                               printf("EXT_CSD:");
> +                               for (i = 0; i < MMC_MAX_BLOCK_LEN; i++) {
> +                                       if (!(i % 10))
> +                                               printf("\n%03i: ", i);
> +                                       printf(" %02x", ext_csd[i]);
> +                               }
> +                               printf("\n");
> +                               return CMD_RET_SUCCESS;
> +                       }
> +                       off = simple_strtoul(argv[3], NULL, 10);
> +                       if (off > 512)
> +                               return CMD_RET_USAGE;
> +                       printf("EXT_CSD[%i]: 0x%02x\n", off, ext_csd[off]);
> +                       if (argv[4])
> +                               env_set_hex(argv[4], ext_csd[off]);
> +                       return CMD_RET_SUCCESS;
> +               }
> +       }
> +
> +       return CMD_RET_FAILURE;
> +}
> +#endif
> +
>  static int do_mmc_boot_wp(struct cmd_tbl *cmdtp, int flag,
>                           int argc, char * const argv[])
>  {
> @@ -963,6 +1050,9 @@ static struct cmd_tbl cmd_mmc[] = {
>  #ifdef CONFIG_CMD_BKOPS_ENABLE
>         U_BOOT_CMD_MKENT(bkops-enable, 2, 0, do_mmc_bkops_enable, "", ""),
>  #endif
> +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> +       U_BOOT_CMD_MKENT(reg, 5, 0, do_mmc_reg, "", ""),
> +#endif
>  };
>
>  static int do_mmcops(struct cmd_tbl *cmdtp, int flag, int argc,
> @@ -1037,6 +1127,10 @@ U_BOOT_CMD(
>  #ifdef CONFIG_CMD_BKOPS_ENABLE
>         "mmc bkops-enable <dev> - enable background operations handshake on device\n"
>         "   WARNING: This is a write-once setting.\n"
> +#endif
> +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> +       "mmc reg read <reg> <offset> [env] - read card register <reg> offset <offset>\n"
> +       "   (optionally into [env] variable)\n"
>  #endif
>         );
>
> --
> 2.27.0
>
Michael Trimarchi June 21, 2020, 7:10 a.m. UTC | #2 
Hi

On Sat, Jun 20, 2020 at 2:35 PM Michael Nazzareno Trimarchi
<michael at amarulasolutions.com> wrote:
>
> Hi
>
> On Sat, Jun 20, 2020 at 2:30 PM Marek Vasut <marex at denx.de> wrote:
> >
> > Add extension to the 'mmc' command to read out the card registers.
> > Currently, only the eMMC OCR/CID/CSD/EXTCSD/RCA/DSR register are
> > supported. A register value can either be displayed or read into
> > an environment variable.
> >
> > Signed-off-by: Marek Vasut <marex at denx.de>
> > ---
> >  cmd/Kconfig |  8 +++++
> >  cmd/mmc.c   | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 102 insertions(+)
> >
> > diff --git a/cmd/Kconfig b/cmd/Kconfig
> > index 192b3b262f..a0cf03c911 100644
> > --- a/cmd/Kconfig
> > +++ b/cmd/Kconfig
> > @@ -1104,6 +1104,14 @@ config CMD_BKOPS_ENABLE
> >           on a eMMC device. The feature is optionally available on eMMC devices
> >           conforming to standard >= 4.41.
> >
> > +config CMD_MMC_REG
> > +       bool "Enable support for reading card registers in the mmc command"
> > +       depends on CMD_MMC
> > +       default y
> > +       help
> > +         Enable the commands for reading card registers. This is useful
> > +         mostly for debugging or extracting details from the card.
> > +
> >  config CMD_MMC_RPMB
> >         bool "Enable support for RPMB in the mmc command"
> >         depends on SUPPORT_EMMC_RPMB
> > diff --git a/cmd/mmc.c b/cmd/mmc.c
> > index 1529a3e05d..55fbfe822e 100644
> > --- a/cmd/mmc.c
> > +++ b/cmd/mmc.c
> > @@ -912,6 +912,93 @@ static int do_mmc_bkops_enable(struct cmd_tbl *cmdtp, int flag,
> >  }
> >  #endif
> >
> > +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> > +static int do_mmc_reg(struct cmd_tbl *cmdtp, int flag,
> > +                        int argc, char *const argv[])
> > +{
> > +       ALLOC_CACHE_ALIGN_BUFFER(u8, ext_csd, MMC_MAX_BLOCK_LEN);
> > +       struct mmc *mmc;
> > +       int i, ret;
> > +       u32 off;
> > +
> > +       if (argc < 3 || argc > 5)
> > +               return CMD_RET_USAGE;
> > +
> > +       mmc = find_mmc_device(curr_device);
> > +       if (!mmc) {
> > +               printf("no mmc device at slot %x\n", curr_device);
> > +               return CMD_RET_FAILURE;
> > +       }
> > +
> > +       if (IS_SD(mmc)) {
> > +               printf("SD registers are not supported\n");
> > +               return CMD_RET_FAILURE;
> > +       } else {
>
> else is not needed
>
> > +               off = simple_strtoul(argv[3], NULL, 10);
> > +               if (!strcmp(argv[2], "cid")) {
> > +                       if (off > 1)
> > +                               return CMD_RET_USAGE;
> > +                       printf("CID[%i]: 0x%08x\n", off, mmc->cid[off]);
> > +                       if (argv[4])
> > +                               env_set_hex(argv[4], mmc->cid[off]);
> > +                       return CMD_RET_SUCCESS;
> > +               }
> > +               if (!strcmp(argv[2], "csd")) {
> > +                       if (off > 3)
> > +                               return CMD_RET_USAGE;
> > +                       printf("CSD[%i]: 0x%08x\n", off, mmc->csd[off]);
> > +                       if (argv[4])
> > +                               env_set_hex(argv[4], mmc->csd[off]);
> > +                       return CMD_RET_SUCCESS;
> > +               }
> > +               if (!strcmp(argv[2], "dsr")) {
> > +                       printf("DSR: 0x%08x\n", mmc->dsr);
> > +                       if (argv[4])
> > +                               env_set_hex(argv[4], mmc->dsr);
> > +                       return CMD_RET_SUCCESS;
> > +               }
> > +               if (!strcmp(argv[2], "ocr")) {
> > +                       printf("OCR: 0x%08x\n", mmc->ocr);
> > +                       if (argv[4])
> > +                               env_set_hex(argv[4], mmc->ocr);
> > +                       return CMD_RET_SUCCESS;
> > +               }
> > +               if (!strcmp(argv[2], "rca")) {
> > +                       printf("RCA: 0x%08x\n", mmc->rca);
> > +                       if (argv[4])
> > +                               env_set_hex(argv[4], mmc->rca);
> > +                       return CMD_RET_SUCCESS;
> > +               }
> > +               if (!strcmp(argv[2], "extcsd") &&
> > +                   mmc->version >= MMC_VERSION_4_41) {
>
> Can you factorize all the conditions?
> string, function
>
> Even use strcmp("extcsd", arg

Sorry for the last comment, I was a bit sleeping

Michael

>
> Michael
>
> > +                       ret = mmc_send_ext_csd(mmc, ext_csd);
> > +                       if (ret)
> > +                               return ret;
> > +                       if (!strcmp(argv[3], "all")) {
> > +                               /* Dump the entire register */
> > +                               printf("EXT_CSD:");
> > +                               for (i = 0; i < MMC_MAX_BLOCK_LEN; i++) {
> > +                                       if (!(i % 10))
> > +                                               printf("\n%03i: ", i);
> > +                                       printf(" %02x", ext_csd[i]);
> > +                               }
> > +                               printf("\n");
> > +                               return CMD_RET_SUCCESS;
> > +                       }
> > +                       off = simple_strtoul(argv[3], NULL, 10);
> > +                       if (off > 512)
> > +                               return CMD_RET_USAGE;
> > +                       printf("EXT_CSD[%i]: 0x%02x\n", off, ext_csd[off]);
> > +                       if (argv[4])
> > +                               env_set_hex(argv[4], ext_csd[off]);
> > +                       return CMD_RET_SUCCESS;
> > +               }
> > +       }
> > +
> > +       return CMD_RET_FAILURE;
> > +}
> > +#endif
> > +
> >  static int do_mmc_boot_wp(struct cmd_tbl *cmdtp, int flag,
> >                           int argc, char * const argv[])
> >  {
> > @@ -963,6 +1050,9 @@ static struct cmd_tbl cmd_mmc[] = {
> >  #ifdef CONFIG_CMD_BKOPS_ENABLE
> >         U_BOOT_CMD_MKENT(bkops-enable, 2, 0, do_mmc_bkops_enable, "", ""),
> >  #endif
> > +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> > +       U_BOOT_CMD_MKENT(reg, 5, 0, do_mmc_reg, "", ""),
> > +#endif
> >  };
> >
> >  static int do_mmcops(struct cmd_tbl *cmdtp, int flag, int argc,
> > @@ -1037,6 +1127,10 @@ U_BOOT_CMD(
> >  #ifdef CONFIG_CMD_BKOPS_ENABLE
> >         "mmc bkops-enable <dev> - enable background operations handshake on device\n"
> >         "   WARNING: This is a write-once setting.\n"
> > +#endif
> > +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> > +       "mmc reg read <reg> <offset> [env] - read card register <reg> offset <offset>\n"
> > +       "   (optionally into [env] variable)\n"
> >  #endif
> >         );
> >
> > --
> > 2.27.0
> >
>
>
> --
> | Michael Nazzareno Trimarchi                     Amarula Solutions BV |
> | COO  -  Founder                                      Cruquiuskade 47 |
> | +31(0)851119172                                 Amsterdam 1018 AM NL |
> |                  [`as] http://www.amarulasolutions.com               |



--
| Michael Nazzareno Trimarchi                     Amarula Solutions BV |
| COO  -  Founder                                      Cruquiuskade 47 |
| +31(0)851119172                                 Amsterdam 1018 AM NL |
|                  [`as] http://www.amarulasolutions.com               |
Peng Fan June 24, 2020, 5:40 a.m. UTC | #3 
Hi Marek,

> Subject: [PATCH] cmd: mmc: Add mmc reg read command for reading card
> registers

This patch breaks ci build.

+u-boot.imx exceeds file size limit:
+  limit:  0x5fc00 bytes
+  actual: 0x60c00 bytes
+  excess: 0x1000 bytes
+make[1]: *** [Makefile:1204: u-boot.imx] Error 1
+make[1]: *** Deleting file 'u-boot.imx'
+make: *** [Makefile:167: sub-make] Error 2

Regards,
Peng.

> 
> Add extension to the 'mmc' command to read out the card registers.
> Currently, only the eMMC OCR/CID/CSD/EXTCSD/RCA/DSR register are
> supported. A register value can either be displayed or read into an
> environment variable.
> 
> Signed-off-by: Marek Vasut <marex at denx.de>
> ---
>  cmd/Kconfig |  8 +++++
>  cmd/mmc.c   | 94
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 102 insertions(+)
> 
> diff --git a/cmd/Kconfig b/cmd/Kconfig
> index 192b3b262f..a0cf03c911 100644
> --- a/cmd/Kconfig
> +++ b/cmd/Kconfig
> @@ -1104,6 +1104,14 @@ config CMD_BKOPS_ENABLE
>  	  on a eMMC device. The feature is optionally available on eMMC
> devices
>  	  conforming to standard >= 4.41.
> 
> +config CMD_MMC_REG
> +	bool "Enable support for reading card registers in the mmc command"
> +	depends on CMD_MMC
> +	default y
> +	help
> +	  Enable the commands for reading card registers. This is useful
> +	  mostly for debugging or extracting details from the card.
> +
>  config CMD_MMC_RPMB
>  	bool "Enable support for RPMB in the mmc command"
>  	depends on SUPPORT_EMMC_RPMB
> diff --git a/cmd/mmc.c b/cmd/mmc.c
> index 1529a3e05d..55fbfe822e 100644
> --- a/cmd/mmc.c
> +++ b/cmd/mmc.c
> @@ -912,6 +912,93 @@ static int do_mmc_bkops_enable(struct cmd_tbl
> *cmdtp, int flag,  }  #endif
> 
> +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> +static int do_mmc_reg(struct cmd_tbl *cmdtp, int flag,
> +			 int argc, char *const argv[])
> +{
> +	ALLOC_CACHE_ALIGN_BUFFER(u8, ext_csd, MMC_MAX_BLOCK_LEN);
> +	struct mmc *mmc;
> +	int i, ret;
> +	u32 off;
> +
> +	if (argc < 3 || argc > 5)
> +		return CMD_RET_USAGE;
> +
> +	mmc = find_mmc_device(curr_device);
> +	if (!mmc) {
> +		printf("no mmc device at slot %x\n", curr_device);
> +		return CMD_RET_FAILURE;
> +	}
> +
> +	if (IS_SD(mmc)) {
> +		printf("SD registers are not supported\n");
> +		return CMD_RET_FAILURE;
> +	} else {
> +		off = simple_strtoul(argv[3], NULL, 10);
> +		if (!strcmp(argv[2], "cid")) {
> +			if (off > 1)
> +				return CMD_RET_USAGE;
> +			printf("CID[%i]: 0x%08x\n", off, mmc->cid[off]);
> +			if (argv[4])
> +				env_set_hex(argv[4], mmc->cid[off]);
> +			return CMD_RET_SUCCESS;
> +		}
> +		if (!strcmp(argv[2], "csd")) {
> +			if (off > 3)
> +				return CMD_RET_USAGE;
> +			printf("CSD[%i]: 0x%08x\n", off, mmc->csd[off]);
> +			if (argv[4])
> +				env_set_hex(argv[4], mmc->csd[off]);
> +			return CMD_RET_SUCCESS;
> +		}
> +		if (!strcmp(argv[2], "dsr")) {
> +			printf("DSR: 0x%08x\n", mmc->dsr);
> +			if (argv[4])
> +				env_set_hex(argv[4], mmc->dsr);
> +			return CMD_RET_SUCCESS;
> +		}
> +		if (!strcmp(argv[2], "ocr")) {
> +			printf("OCR: 0x%08x\n", mmc->ocr);
> +			if (argv[4])
> +				env_set_hex(argv[4], mmc->ocr);
> +			return CMD_RET_SUCCESS;
> +		}
> +		if (!strcmp(argv[2], "rca")) {
> +			printf("RCA: 0x%08x\n", mmc->rca);
> +			if (argv[4])
> +				env_set_hex(argv[4], mmc->rca);
> +			return CMD_RET_SUCCESS;
> +		}
> +		if (!strcmp(argv[2], "extcsd") &&
> +		    mmc->version >= MMC_VERSION_4_41) {
> +			ret = mmc_send_ext_csd(mmc, ext_csd);
> +			if (ret)
> +				return ret;
> +			if (!strcmp(argv[3], "all")) {
> +				/* Dump the entire register */
> +				printf("EXT_CSD:");
> +				for (i = 0; i < MMC_MAX_BLOCK_LEN; i++) {
> +					if (!(i % 10))
> +						printf("\n%03i: ", i);
> +					printf(" %02x", ext_csd[i]);
> +				}
> +				printf("\n");
> +				return CMD_RET_SUCCESS;
> +			}
> +			off = simple_strtoul(argv[3], NULL, 10);
> +			if (off > 512)
> +				return CMD_RET_USAGE;
> +			printf("EXT_CSD[%i]: 0x%02x\n", off, ext_csd[off]);
> +			if (argv[4])
> +				env_set_hex(argv[4], ext_csd[off]);
> +			return CMD_RET_SUCCESS;
> +		}
> +	}
> +
> +	return CMD_RET_FAILURE;
> +}
> +#endif
> +
>  static int do_mmc_boot_wp(struct cmd_tbl *cmdtp, int flag,
>  			  int argc, char * const argv[])
>  {
> @@ -963,6 +1050,9 @@ static struct cmd_tbl cmd_mmc[] = {  #ifdef
> CONFIG_CMD_BKOPS_ENABLE
>  	U_BOOT_CMD_MKENT(bkops-enable, 2, 0, do_mmc_bkops_enable, "",
> ""),  #endif
> +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> +	U_BOOT_CMD_MKENT(reg, 5, 0, do_mmc_reg, "", ""), #endif
>  };
> 
>  static int do_mmcops(struct cmd_tbl *cmdtp, int flag, int argc, @@ -1037,6
> +1127,10 @@ U_BOOT_CMD(  #ifdef CONFIG_CMD_BKOPS_ENABLE
>  	"mmc bkops-enable <dev> - enable background operations handshake
> on device\n"
>  	"   WARNING: This is a write-once setting.\n"
> +#endif
> +#if CONFIG_IS_ENABLED(CMD_MMC_REG)
> +	"mmc reg read <reg> <offset> [env] - read card register <reg> offset
> <offset>\n"
> +	"   (optionally into [env] variable)\n"
>  #endif
>  	);
> 
> --
> 2.27.0
Marek Vasut June 24, 2020, 9:19 a.m. UTC | #4 
On 6/24/20 7:40 AM, Peng Fan wrote:
> Hi Marek,

Hi,

>> Subject: [PATCH] cmd: mmc: Add mmc reg read command for reading card
>> registers
> 
> This patch breaks ci build.
> 
> +u-boot.imx exceeds file size limit:
> +  limit:  0x5fc00 bytes
> +  actual: 0x60c00 bytes
> +  excess: 0x1000 bytes
> +make[1]: *** [Makefile:1204: u-boot.imx] Error 1
> +make[1]: *** Deleting file 'u-boot.imx'
> +make: *** [Makefile:167: sub-make] Error 2

On which board ?
Peng Fan June 24, 2020, 10:15 a.m. UTC | #5 
> Subject: Re: [PATCH] cmd: mmc: Add mmc reg read command for reading card
> registers
> 
> On 6/24/20 7:40 AM, Peng Fan wrote:
> > Hi Marek,
> 
> Hi,
> 
> >> Subject: [PATCH] cmd: mmc: Add mmc reg read command for reading card
> >> registers
> >
> > This patch breaks ci build.
> >
> > +u-boot.imx exceeds file size limit:
> > +  limit:  0x5fc00 bytes
> > +  actual: 0x60c00 bytes
> > +  excess: 0x1000 bytes
> > +make[1]: *** [Makefile:1204: u-boot.imx] Error 1
> > +make[1]: *** Deleting file 'u-boot.imx'
> > +make: *** [Makefile:167: sub-make] Error 2
> 
> On which board ?

arm:  +   tbs2910
Regards,
Peng.
diff mbox series

Patch

diff --git a/cmd/Kconfig b/cmd/Kconfig
index 192b3b262f..a0cf03c911 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1104,6 +1104,14 @@  config CMD_BKOPS_ENABLE
 	  on a eMMC device. The feature is optionally available on eMMC devices
 	  conforming to standard >= 4.41.
 
+config CMD_MMC_REG
+	bool "Enable support for reading card registers in the mmc command"
+	depends on CMD_MMC
+	default y
+	help
+	  Enable the commands for reading card registers. This is useful
+	  mostly for debugging or extracting details from the card.
+
 config CMD_MMC_RPMB
 	bool "Enable support for RPMB in the mmc command"
 	depends on SUPPORT_EMMC_RPMB
diff --git a/cmd/mmc.c b/cmd/mmc.c
index 1529a3e05d..55fbfe822e 100644
--- a/cmd/mmc.c
+++ b/cmd/mmc.c
@@ -912,6 +912,93 @@  static int do_mmc_bkops_enable(struct cmd_tbl *cmdtp, int flag,
 }
 #endif
 
+#if CONFIG_IS_ENABLED(CMD_MMC_REG)
+static int do_mmc_reg(struct cmd_tbl *cmdtp, int flag,
+			 int argc, char *const argv[])
+{
+	ALLOC_CACHE_ALIGN_BUFFER(u8, ext_csd, MMC_MAX_BLOCK_LEN);
+	struct mmc *mmc;
+	int i, ret;
+	u32 off;
+
+	if (argc < 3 || argc > 5)
+		return CMD_RET_USAGE;
+
+	mmc = find_mmc_device(curr_device);
+	if (!mmc) {
+		printf("no mmc device at slot %x\n", curr_device);
+		return CMD_RET_FAILURE;
+	}
+
+	if (IS_SD(mmc)) {
+		printf("SD registers are not supported\n");
+		return CMD_RET_FAILURE;
+	} else {
+		off = simple_strtoul(argv[3], NULL, 10);
+		if (!strcmp(argv[2], "cid")) {
+			if (off > 1)
+				return CMD_RET_USAGE;
+			printf("CID[%i]: 0x%08x\n", off, mmc->cid[off]);
+			if (argv[4])
+				env_set_hex(argv[4], mmc->cid[off]);
+			return CMD_RET_SUCCESS;
+		}
+		if (!strcmp(argv[2], "csd")) {
+			if (off > 3)
+				return CMD_RET_USAGE;
+			printf("CSD[%i]: 0x%08x\n", off, mmc->csd[off]);
+			if (argv[4])
+				env_set_hex(argv[4], mmc->csd[off]);
+			return CMD_RET_SUCCESS;
+		}
+		if (!strcmp(argv[2], "dsr")) {
+			printf("DSR: 0x%08x\n", mmc->dsr);
+			if (argv[4])
+				env_set_hex(argv[4], mmc->dsr);
+			return CMD_RET_SUCCESS;
+		}
+		if (!strcmp(argv[2], "ocr")) {
+			printf("OCR: 0x%08x\n", mmc->ocr);
+			if (argv[4])
+				env_set_hex(argv[4], mmc->ocr);
+			return CMD_RET_SUCCESS;
+		}
+		if (!strcmp(argv[2], "rca")) {
+			printf("RCA: 0x%08x\n", mmc->rca);
+			if (argv[4])
+				env_set_hex(argv[4], mmc->rca);
+			return CMD_RET_SUCCESS;
+		}
+		if (!strcmp(argv[2], "extcsd") &&
+		    mmc->version >= MMC_VERSION_4_41) {
+			ret = mmc_send_ext_csd(mmc, ext_csd);
+			if (ret)
+				return ret;
+			if (!strcmp(argv[3], "all")) {
+				/* Dump the entire register */
+				printf("EXT_CSD:");
+				for (i = 0; i < MMC_MAX_BLOCK_LEN; i++) {
+					if (!(i % 10))
+						printf("\n%03i: ", i);
+					printf(" %02x", ext_csd[i]);
+				}
+				printf("\n");
+				return CMD_RET_SUCCESS;
+			}
+			off = simple_strtoul(argv[3], NULL, 10);
+			if (off > 512)
+				return CMD_RET_USAGE;
+			printf("EXT_CSD[%i]: 0x%02x\n", off, ext_csd[off]);
+			if (argv[4])
+				env_set_hex(argv[4], ext_csd[off]);
+			return CMD_RET_SUCCESS;
+		}
+	}
+
+	return CMD_RET_FAILURE;
+}
+#endif
+
 static int do_mmc_boot_wp(struct cmd_tbl *cmdtp, int flag,
 			  int argc, char * const argv[])
 {
@@ -963,6 +1050,9 @@  static struct cmd_tbl cmd_mmc[] = {
 #ifdef CONFIG_CMD_BKOPS_ENABLE
 	U_BOOT_CMD_MKENT(bkops-enable, 2, 0, do_mmc_bkops_enable, "", ""),
 #endif
+#if CONFIG_IS_ENABLED(CMD_MMC_REG)
+	U_BOOT_CMD_MKENT(reg, 5, 0, do_mmc_reg, "", ""),
+#endif
 };
 
 static int do_mmcops(struct cmd_tbl *cmdtp, int flag, int argc,
@@ -1037,6 +1127,10 @@  U_BOOT_CMD(
 #ifdef CONFIG_CMD_BKOPS_ENABLE
 	"mmc bkops-enable <dev> - enable background operations handshake on device\n"
 	"   WARNING: This is a write-once setting.\n"
+#endif
+#if CONFIG_IS_ENABLED(CMD_MMC_REG)
+	"mmc reg read <reg> <offset> [env] - read card register <reg> offset <offset>\n"
+	"   (optionally into [env] variable)\n"
 #endif
 	);