Change in coreboot[master]: soc/ti/am335x: Add MMC/SD driver

[Sam Lewis (Code Review)]

Sam Lewis has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/44384 )

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

soc/ti/am335x: Add MMC/SD driver

Adds a driver for the am335x MMC peripheral. This has only been tested
with SD cards and probably needs some modification to use eMMC or MMC
cards.

It's also currently a little slow as it only supports reading a block at
a time.

Change-Id: I5c2b250782cddca17aa46cc8222b9aebef505fb2
Signed-off-by: Sam Lewis 
---
A src/soc/ti/am335x/mmc.c
A src/soc/ti/am335x/mmc.h
2 files changed, 311 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/84/44384/1

diff --git a/src/soc/ti/am335x/mmc.c b/src/soc/ti/am335x/mmc.c
new file mode 100644
index 0000000..993fe8c
--- /dev/null
+++ b/src/soc/ti/am335x/mmc.c
@@ -0,0 +1,261 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <inttypes.h>
+#include <string.h>
+#include <console/console.h>
+#include <commonlib/sd_mmc_ctrlr.h>
+#include <device/mmio.h>
+#include "mmc.h"
+
+#define SYSCONFIG_SOFTRESET (0x1 << 1)
+
+#define SYSSTATUS_RESETDONE (0x01 << 0)
+
+#define CON_INIT (0x1 << 1)
+
+#define CMD_INDEX(x) (x << 24)
+#define CMD_RSP_TYPE_NO_RESP (0x0 << 16)
+#define CMD_RSP_TYPE_136B (0x1 << 16)
+#define CMD_RSP_TYPE_48B (0x2 << 16)
+#define CMD_RSP_TYPE_48B_BUSY (0x3 << 16)
+#define CMD_DP_DATA (0x1 << 21)
+#define CMD_DDIR_READ (0x1 << 4)
+
+#define HCTL_DTW_1BIT (0x0 << 1)
+#define HCTL_SDBP (0x1 << 8)
+#define HCTL_SDVS_VS30 (0x6 << 9)
+
+#define SYSCTL_ICE (0x1 << 0)
+#define SYSCTL_ICS (0x1 << 1)
+#define SYSCTL_CEN (0x1 << 2)
+#define SYSCTL_DTO_15 (0xE << 16)
+
+#define STAT_ERRI (0x01 << 15)
+#define STAT_ERROR_MASK (0xff << 15 | 0x3 << 24 | 0x03 << 28)
+#define STAT_CC (0x1 << 0)
+
+#define IE_CC (0x1 << 0)
+#define IE_TC (0x1 << 1)
+#define IE_BRR (0x1 << 5)
+#define IE_ERRORS (0xff << 15 | 0x3 << 24 | 0x03 << 28)
+
+#define CAPA_VS18 (0x01 << 26)
+#define CAPA_VS30 (0x01 << 25)
+
+static int am335x_mmc_init(struct am335x_mmc *mmc)
+{
+	// Follows the initialisiation from the AM335X technical reference manual
+	setbits32(&mmc->sysconfig, SYSCONFIG_SOFTRESET);
+
+	while (!(read32(&mmc->sysstatus) & SYSSTATUS_RESETDONE))
+		;
+
+	setbits32(&mmc->capa, CAPA_VS30);
+	setbits32(&mmc->hctl, HCTL_SDVS_VS30 | HCTL_DTW_1BIT);
+	setbits32(&mmc->hctl, HCTL_SDBP);
+
+	while (!(read32(&mmc->hctl) & HCTL_SDBP))
+		;
+
+	// Assumes the default input clock speed of 96MHz to set a minimum SD
+	// speed of 400 KHz
+	write32(&mmc->sysctl, read32(&mmc->sysctl) | 240 << 6 | SYSCTL_DTO_15);
+
+	setbits32(&mmc->sysctl, SYSCTL_ICE | SYSCTL_CEN);
+
+	while (!(read32(&mmc->sysctl) & SYSCTL_ICS))
+		;
+
+	write32(&mmc->ie, IE_ERRORS | IE_TC | IE_CC);
+
+	// Clear interrupts
+	write32(&mmc->stat, 0xffffffffu);
+
+	setbits32(&mmc->con, CON_INIT);
+	write32(&mmc->cmd, 0x00);
+
+	while (!(read32(&mmc->stat) & STAT_CC))
+		;
+
+	write32(&mmc->stat, 0xffffffffu);
+	clrbits32(&mmc->con, CON_INIT);
+
+	return 0;
+}
+
+static int am335x_send_cmd(struct sd_mmc_ctrlr *ctrlr, struct mmc_command *cmd,
+			   struct mmc_data *data)
+{
+	struct am335x_mmc_host *mmc;
+	struct am335x_mmc *reg;
+
+	mmc = container_of(ctrlr, struct am335x_mmc_host, sd_mmc_ctrlr);
+	reg = mmc->reg;
+
+	if (read32(&reg->stat)) {
+		printk(BIOS_WARNING, "AM335X MMC: Interrupt already raised\n");
+		return 1;
+	}
+
+	uint32_t transfer_type = 0;
+
+	if (data) {
+		if (data->flags & DATA_FLAG_READ) {
+			setbits32(&mmc->reg->ie, IE_BRR);
+			write32(&mmc->reg->blk, data->blocksize);
+			transfer_type |= CMD_DP_DATA | CMD_DDIR_READ;
+		}
+
+		if (data->flags & DATA_FLAG_WRITE) {
+			printk(BIOS_ERR, "AM335X MMC: Writes currently not supported\n");
+			return 1;
+		}
+	}
+
+	switch (cmd->resp_type) {
+	case CARD_RSP_R1b:
+		transfer_type |= CMD_RSP_TYPE_48B_BUSY;
+		break;
+	case CARD_RSP_R1:
+	case CARD_RSP_R3:
+		transfer_type |= CMD_RSP_TYPE_48B;
+		break;
+	case CARD_RSP_R2:
+		transfer_type |= CMD_RSP_TYPE_136B;
+		break;
+	case CARD_RSP_NONE:
+		transfer_type |= CMD_RSP_TYPE_NO_RESP;
+		break;
+	default:
+		printk(BIOS_ERR, "AM335X MMC: Unknown response type\n");
+		return 1;
+	}
+
+	if (cmd->cmdidx == MMC_CMD_SET_BLOCKLEN) {
+		// todo: Support bigger blocks for faster transfers
+		return 0;
+	}
+
+	write32(&reg->arg, cmd->cmdarg);
+	write32(&reg->cmd, CMD_INDEX(cmd->cmdidx) | transfer_type);
+
+	// Wait for any interrupt
+	while (!read32(&reg->stat))
+		;
+
+	// Check to ensure that there was not any errors
+	if (read32(&reg->stat) & STAT_ERRI) {
+		printk(BIOS_WARNING, "AM335X MMC: Error while reading %08x\n",
+		       read32(&reg->stat));
+
+		// Clear the errors
+		write32(&reg->stat, STAT_ERROR_MASK);
+		return 1;
+	}
+
+	if (cmd->resp_type == CARD_RSP_R1b) {
+		while (!(read32(&reg->stat) & IE_TC))
+			;
+		write32(&reg->stat, IE_TC);
+	}
+
+	write32(&reg->stat, IE_CC);
+
+	switch (cmd->resp_type) {
+	case CARD_RSP_R1:
+	case CARD_RSP_R1b:
+	case CARD_RSP_R3:
+		cmd->response[0] = read32(&reg->rsp10);
+		break;
+	case CARD_RSP_R2:
+		cmd->response[3] = read32(&reg->rsp10);
+		cmd->response[2] = read32(&reg->rsp32);
+		cmd->response[1] = read32(&reg->rsp54);
+		cmd->response[0] = read32(&reg->rsp76);
+		break;
+	case CARD_RSP_NONE:
+		break;
+	}
+
+	if (data != NULL && data->flags & DATA_FLAG_READ) {
+		while (!(read32(&reg->stat) & IE_BRR))
+			;
+
+		uint32_t *dest32 = (uint32_t *)data->dest;
+
+		for (int count = 0; count < data->blocksize; count += 4) {
+			*dest32 = read32(&reg->data);
+			dest32++;
+		}
+
+		write32(&reg->stat, IE_TC);
+		write32(&reg->stat, IE_BRR);
+		clrbits32(&reg->ie, IE_BRR);
+	}
+
+	return 0;
+}
+
+static void set_ios(struct sd_mmc_ctrlr *ctrlr)
+{
+	struct am335x_mmc_host *mmc;
+	struct am335x_mmc *reg;
+
+	mmc = container_of(ctrlr, struct am335x_mmc_host, sd_mmc_ctrlr);
+	reg = mmc->reg;
+
+	if (ctrlr->request_hz != ctrlr->bus_hz) {
+		uint32_t requested_hz = ctrlr->request_hz;
+
+		requested_hz = MIN(requested_hz, ctrlr->f_min);
+		requested_hz = MAX(requested_hz, ctrlr->f_max);
+
+		uint32_t divisor = mmc->sd_clock_hz / requested_hz;
+		uint32_t actual = mmc->sd_clock_hz * divisor;
+
+		if (actual != ctrlr->bus_hz) {
+			clrbits32(&reg->sysctl, SYSCTL_CEN);
+
+			uint32_t new_sysctl = read32(&reg->sysctl);
+			new_sysctl &= ~(0x3ff << 6);
+			new_sysctl |= ((divisor & 0x3ff) << 6);
+
+			write32(&reg->sysctl, new_sysctl);
+
+			// Wait for clock stability
+			while (!(read32(&reg->sysctl) & SYSCTL_ICS))
+				;
+
+			setbits32(&reg->sysctl, SYSCTL_CEN);
+
+			ctrlr->bus_hz = mmc->sd_clock_hz / divisor;
+		}
+	}
+}
+
+int am335x_mmc_init_storage(struct am335x_mmc_host *mmc_host)
+{
+	int err = 0;
+
+	struct sd_mmc_ctrlr *mmc_ctrlr = &mmc_host->sd_mmc_ctrlr;
+	memset(mmc_ctrlr, 0, sizeof(mmc_ctrlr));
+
+
+	err = am335x_mmc_init(mmc_host->reg);
+	if (err != 0) {
+		printk(BIOS_ERR, "ERROR: Initialising AM335X SD failed.\n");
+		return err;
+	}
+
+	mmc_ctrlr->send_cmd = &am335x_send_cmd;
+	mmc_ctrlr->set_ios = &set_ios;
+
+	mmc_ctrlr->voltages = MMC_VDD_30_31;
+	mmc_ctrlr->b_max = 1;
+	mmc_ctrlr->bus_width = 1;
+	mmc_ctrlr->f_max = 48000000;
+	mmc_ctrlr->f_min = 400000;
+	mmc_ctrlr->bus_hz = 400000;
+
+	return 0;
+}
diff --git a/src/soc/ti/am335x/mmc.h b/src/soc/ti/am335x/mmc.h
new file mode 100644
index 0000000..761aa4e
--- /dev/null
+++ b/src/soc/ti/am335x/mmc.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef AM335X_MMC_H
+#define AM335X_MMC_H
+
+#include <inttypes.h>
+#include <commonlib/sd_mmc_ctrlr.h>
+
+#define MMCHS0_BASE 0x48060000
+
+struct am335x_mmc {
+	uint8_t res1[0x110];
+	uint32_t sysconfig;
+	uint32_t sysstatus;
+	uint8_t res2[0x14];
+	uint32_t con;
+	uint32_t pwcnt;
+	uint32_t dll;
+	uint8_t res3[0xcc];
+	uint32_t blk;
+	uint32_t arg;
+	uint32_t cmd;
+	uint32_t rsp10;
+	uint32_t rsp32;
+	uint32_t rsp54;
+	uint32_t rsp76;
+	uint32_t data;
+	uint32_t pstate;
+	uint32_t hctl;
+	uint32_t sysctl;
+	uint32_t stat;
+	uint32_t ie;
+	uint8_t res4[0x4];
+	uint32_t ac12;
+	uint32_t capa;
+	uint32_t capa2;
+	uint8_t res5[0xc];
+	uint32_t admaes;
+	uint32_t admasal;
+};
+
+struct am335x_mmc_host {
+	struct sd_mmc_ctrlr sd_mmc_ctrlr;
+	struct am335x_mmc *reg;
+	uint32_t sd_clock_hz;
+};
+
+int am335x_mmc_init_storage(struct am335x_mmc_host *mmc_host);
+
+#endif

[Sam Lewis (Code Review)]

Hello build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/44384

to look at the new patch set (#2).

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

soc/ti/am335x: Add MMC/SD driver

Adds a driver for the am335x MMC peripheral. This has only been tested
with SD cards and probably needs some modification to use eMMC or MMC
cards.

It's also currently a little slow as it only supports reading a block at
a time.

Change-Id: I5c2b250782cddca17aa46cc8222b9aebef505fb2
Signed-off-by: Sam Lewis 
---
A src/soc/ti/am335x/mmc.c
A src/soc/ti/am335x/mmc.h
2 files changed, 311 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/84/44384/2

[Sam Lewis (Code Review)]

Hello build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/44384

to look at the new patch set (#9).

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

soc/ti/am335x: Add MMC/SD driver

Adds a driver for the am335x MMC peripheral. This has only been tested
with SD cards and probably needs some modification to use eMMC or MMC
cards.

It's also currently a little slow as it only supports reading a block at
a time.

Change-Id: I5c2b250782cddca17aa46cc8222b9aebef505fb2
Signed-off-by: Sam Lewis 
---
M src/mainboard/ti/beaglebone/Kconfig
M src/mainboard/ti/beaglebone/Makefile.inc
A src/mainboard/ti/beaglebone/board.fmd
A src/mainboard/ti/beaglebone/sd_media.c
M src/soc/ti/am335x/Makefile.inc
D src/soc/ti/am335x/bootblock_media.c
M src/soc/ti/am335x/header.c
M src/soc/ti/am335x/header.h
M src/soc/ti/am335x/memlayout.ld
A src/soc/ti/am335x/mmc.c
A src/soc/ti/am335x/mmc.h
D src/soc/ti/am335x/nand.c
12 files changed, 483 insertions(+), 47 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/84/44384/9

[Sam Lewis (Code Review)]

Hello build bot (Jenkins), Patrick Georgi, Martin Roth, Julius Werner,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/44384

to look at the new patch set (#10).

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

soc/ti/am335x: Add MMC/SD driver

Adds a driver for the am335x MMC peripheral. This has only been tested
with SD cards and probably needs some modification to use eMMC or MMC
cards.

It's also currently a little slow as it only supports reading a block at
a time.

Change-Id: I5c2b250782cddca17aa46cc8222b9aebef505fb2
Signed-off-by: Sam Lewis 
---
A src/soc/ti/am335x/mmc.c
A src/soc/ti/am335x/mmc.h
2 files changed, 311 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/84/44384/10

[Arthur Heymans (Code Review)]

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/44384 )

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

Patch Set 10: Code-Review+2

(2 comments)

https://review.coreboot.org/c/coreboot/+/44384/10/src/soc/ti/am335x/mmc.h 
File src/soc/ti/am335x/mmc.h:

https://review.coreboot.org/c/coreboot/+/44384/10/src/soc/ti/am335x/mmc.h@11 
PS10, Line 11: struct am335x_mmc {
             : 	uint8_t res1[0x110];
             : 	uint32_t sysconfig;
             : 	uint32_t sysstatus;
             : 	uint8_t res2[0x14];
             : 	uint32_t con;
             : 	uint32_t pwcnt;
             : 	uint32_t dll;
             : 	uint8_t res3[0xcc];
             : 	uint32_t blk;
             : 	uint32_t arg;
             : 	uint32_t cmd;
             : 	uint32_t rsp10;
             : 	uint32_t rsp32;
             : 	uint32_t rsp54;
             : 	uint32_t rsp76;
             : 	uint32_t data;
             : 	uint32_t pstate;
             : 	uint32_t hctl;
             : 	uint32_t sysctl;
             : 	uint32_t stat;
             : 	uint32_t ie;
             : 	uint8_t res4[0x4];
             : 	uint32_t ac12;
             : 	uint32_t capa;
             : 	uint32_t capa2;
             : 	uint8_t res5[0xc];
             : 	uint32_t admaes;
             : 	uint32_t admasal;
             : };
You might want to use the __packed directive?

https://review.coreboot.org/c/coreboot/+/44384/10/src/soc/ti/am335x/mmc.c 
File src/soc/ti/am335x/mmc.c:

https://review.coreboot.org/c/coreboot/+/44384/10/src/soc/ti/am335x/mmc.c@50 
PS10, Line 50: while (!(read32(&mmc->sysstatus) & SYSSTATUS_RESETDONE))
             : 		;
It would be nicer with timeouts.

[Paul Menzel (Code Review)]

Attention is currently required from: Sam Lewis.
Paul Menzel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/44384 )

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

Patch Set 10:

(1 comment)

Patchset:

PS10: 
Sam, to get this committed, are you planning on addressing Arthur’s comments, or should it be submitted as is?

[Sam Lewis (Code Review)]

Attention is currently required from: Sam Lewis.
Hello build bot (Jenkins), Patrick Georgi, Martin Roth, Julius Werner, Arthur Heymans,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/44384

to look at the new patch set (#11).

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

soc/ti/am335x: Add MMC/SD driver

Adds a driver for the am335x MMC peripheral. This has only been tested
with SD cards and probably needs some modification to use eMMC or MMC
cards.

It's also currently a little slow as it only supports reading a block at
a time.

Change-Id: I5c2b250782cddca17aa46cc8222b9aebef505fb2
Signed-off-by: Sam Lewis 
---
A src/soc/ti/am335x/mmc.c
A src/soc/ti/am335x/mmc.h
2 files changed, 333 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/84/44384/11

[Sam Lewis (Code Review)]

Attention is currently required from: Paul Menzel, Arthur Heymans.
Sam Lewis has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/44384 )

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

Patch Set 11:

(3 comments)

Patchset:

PS10:
> Sam, to get this committed, are you planning on addressing Arthur’s comments, or should it be submit […]

I've addressed Arthur's comments and it should be good to be merged now. Sorry for taking so long!

File src/soc/ti/am335x/mmc.h:

https://review.coreboot.org/c/coreboot/+/44384/comment/a7072a06_46f0f34c 
PS10, Line 11: struct am335x_mmc {
             : 	uint8_t res1[0x110];
             : 	uint32_t sysconfig;
             : 	uint32_t sysstatus;
             : 	uint8_t res2[0x14];
             : 	uint32_t con;
             : 	uint32_t pwcnt;
             : 	uint32_t dll;
             : 	uint8_t res3[0xcc];
             : 	uint32_t blk;
             : 	uint32_t arg;
             : 	uint32_t cmd;
             : 	uint32_t rsp10;
             : 	uint32_t rsp32;
             : 	uint32_t rsp54;
             : 	uint32_t rsp76;
             : 	uint32_t data;
             : 	uint32_t pstate;
             : 	uint32_t hctl;
             : 	uint32_t sysctl;
             : 	uint32_t stat;
             : 	uint32_t ie;
             : 	uint8_t res4[0x4];
             : 	uint32_t ac12;
             : 	uint32_t capa;
             : 	uint32_t capa2;
             : 	uint8_t res5[0xc];
             : 	uint32_t admaes;
             : 	uint32_t admasal;
             : };
> You might want to use the __packed directive?

Done

File src/soc/ti/am335x/mmc.c:

https://review.coreboot.org/c/coreboot/+/44384/comment/69b95af2_7322536a 
PS10, Line 50: while (!(read32(&mmc->sysstatus) & SYSSTATUS_RESETDONE))
             : 		;
> It would be nicer with timeouts.

Have now added a rudimentary timeout for all of the polling register loops.

[Arthur Heymans (Code Review)]

Attention is currently required from: Sam Lewis, Paul Menzel.
Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/44384 )

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

Patch Set 11: Code-Review+2

[Arthur Heymans (Code Review)]

Arthur Heymans has submitted this change. ( https://review.coreboot.org/c/coreboot/+/44384 )

Change subject: soc/ti/am335x: Add MMC/SD driver
......................................................................

soc/ti/am335x: Add MMC/SD driver

Adds a driver for the am335x MMC peripheral. This has only been tested
with SD cards and probably needs some modification to use eMMC or MMC
cards.

It's also currently a little slow as it only supports reading a block at
a time.

Change-Id: I5c2b250782cddca17aa46cc8222b9aebef505fb2
Signed-off-by: Sam Lewis 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44384
Tested-by: build bot (Jenkins) 
Reviewed-by: Arthur Heymans 
---
A src/soc/ti/am335x/mmc.c
A src/soc/ti/am335x/mmc.h
2 files changed, 333 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Arthur Heymans: Looks good to me, approved

diff --git a/src/soc/ti/am335x/mmc.c b/src/soc/ti/am335x/mmc.c
new file mode 100644
index 0000000..395cf4f
--- /dev/null
+++ b/src/soc/ti/am335x/mmc.c
@@ -0,0 +1,283 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <inttypes.h>
+#include <string.h>
+#include <console/console.h>
+#include <commonlib/sd_mmc_ctrlr.h>
+#include <device/mmio.h>
+#include <timer.h>
+#include "mmc.h"
+
+#define AM335X_TIMEOUT_MSEC 1000
+
+#define SYSCONFIG_SOFTRESET (0x1 << 1)
+
+#define SYSSTATUS_RESETDONE (0x01 << 0)
+
+#define CON_INIT (0x1 << 1)
+
+#define CMD_INDEX(x) (x << 24)
+#define CMD_RSP_TYPE_NO_RESP (0x0 << 16)
+#define CMD_RSP_TYPE_136B (0x1 << 16)
+#define CMD_RSP_TYPE_48B (0x2 << 16)
+#define CMD_RSP_TYPE_48B_BUSY (0x3 << 16)
+#define CMD_DP_DATA (0x1 << 21)
+#define CMD_DDIR_READ (0x1 << 4)
+
+#define HCTL_DTW_1BIT (0x0 << 1)
+#define HCTL_SDBP (0x1 << 8)
+#define HCTL_SDVS_VS30 (0x6 << 9)
+
+#define SYSCTL_ICE (0x1 << 0)
+#define SYSCTL_ICS (0x1 << 1)
+#define SYSCTL_CEN (0x1 << 2)
+#define SYSCTL_DTO_15 (0xE << 16)
+
+#define STAT_ERRI (0x01 << 15)
+#define STAT_ERROR_MASK (0xff << 15 | 0x3 << 24 | 0x03 << 28)
+#define STAT_CC (0x1 << 0)
+
+#define IE_CC (0x1 << 0)
+#define IE_TC (0x1 << 1)
+#define IE_BRR (0x1 << 5)
+#define IE_ERRORS (0xff << 15 | 0x3 << 24 | 0x03 << 28)
+
+#define CAPA_VS18 (0x01 << 26)
+#define CAPA_VS30 (0x01 << 25)
+
+static int am335x_wait_for_reg(const void *addr, uint32_t mask, unsigned long timeout)
+{
+	struct mono_time current, end;
+
+	timer_monotonic_get(&current);
+	end = current;
+	mono_time_add_msecs(&end, timeout);
+
+	do {
+		if ((read32(addr) & mask))
+			return 0;
+
+		timer_monotonic_get(&current);
+	} while (!mono_time_after(&current, &end));
+
+	printk(BIOS_DEBUG, "am335x MMC timeout: %ld msec\n", timeout);
+	return -1;
+}
+
+static int am335x_mmc_init(struct am335x_mmc *mmc)
+{
+	// Follows the initialisiation from the AM335X technical reference manual
+	setbits32(&mmc->sysconfig, SYSCONFIG_SOFTRESET);
+
+	if (am335x_wait_for_reg(&mmc->sysstatus, SYSSTATUS_RESETDONE, AM335X_TIMEOUT_MSEC))
+		return -1;
+
+	setbits32(&mmc->capa, CAPA_VS30);
+	setbits32(&mmc->hctl, HCTL_SDVS_VS30 | HCTL_DTW_1BIT);
+	setbits32(&mmc->hctl, HCTL_SDBP);
+
+	if (am335x_wait_for_reg(&mmc->hctl, HCTL_SDBP, AM335X_TIMEOUT_MSEC))
+		return -1;
+
+	// Assumes the default input clock speed of 96MHz to set a minimum SD
+	// speed of 400 KHz
+	write32(&mmc->sysctl, read32(&mmc->sysctl) | 240 << 6 | SYSCTL_DTO_15);
+
+	setbits32(&mmc->sysctl, SYSCTL_ICE | SYSCTL_CEN);
+
+	if (am335x_wait_for_reg(&mmc->sysctl, SYSCTL_ICS, AM335X_TIMEOUT_MSEC))
+		return -1;
+
+	write32(&mmc->ie, IE_ERRORS | IE_TC | IE_CC);
+
+	// Clear interrupts
+	write32(&mmc->stat, 0xffffffffu);
+
+	setbits32(&mmc->con, CON_INIT);
+	write32(&mmc->cmd, 0x00);
+
+	if (am335x_wait_for_reg(&mmc->stat, STAT_CC, AM335X_TIMEOUT_MSEC))
+		return -1;
+
+	write32(&mmc->stat, 0xffffffffu);
+	clrbits32(&mmc->con, CON_INIT);
+
+	return 0;
+}
+
+static int am335x_send_cmd(struct sd_mmc_ctrlr *ctrlr, struct mmc_command *cmd,
+			   struct mmc_data *data)
+{
+	struct am335x_mmc_host *mmc;
+	struct am335x_mmc *reg;
+
+	mmc = container_of(ctrlr, struct am335x_mmc_host, sd_mmc_ctrlr);
+	reg = mmc->reg;
+
+	if (read32(&reg->stat)) {
+		printk(BIOS_WARNING, "AM335X MMC: Interrupt already raised\n");
+		return 1;
+	}
+
+	uint32_t transfer_type = 0;
+
+	if (data) {
+		if (data->flags & DATA_FLAG_READ) {
+			setbits32(&mmc->reg->ie, IE_BRR);
+			write32(&mmc->reg->blk, data->blocksize);
+			transfer_type |= CMD_DP_DATA | CMD_DDIR_READ;
+		}
+
+		if (data->flags & DATA_FLAG_WRITE) {
+			printk(BIOS_ERR, "AM335X MMC: Writes currently not supported\n");
+			return 1;
+		}
+	}
+
+	switch (cmd->resp_type) {
+	case CARD_RSP_R1b:
+		transfer_type |= CMD_RSP_TYPE_48B_BUSY;
+		break;
+	case CARD_RSP_R1:
+	case CARD_RSP_R3:
+		transfer_type |= CMD_RSP_TYPE_48B;
+		break;
+	case CARD_RSP_R2:
+		transfer_type |= CMD_RSP_TYPE_136B;
+		break;
+	case CARD_RSP_NONE:
+		transfer_type |= CMD_RSP_TYPE_NO_RESP;
+		break;
+	default:
+		printk(BIOS_ERR, "AM335X MMC: Unknown response type\n");
+		return 1;
+	}
+
+	if (cmd->cmdidx == MMC_CMD_SET_BLOCKLEN) {
+		// todo: Support bigger blocks for faster transfers
+		return 0;
+	}
+
+	write32(&reg->arg, cmd->cmdarg);
+	write32(&reg->cmd, CMD_INDEX(cmd->cmdidx) | transfer_type);
+
+	// Wait for any interrupt
+	if (am335x_wait_for_reg(&reg->stat, 0xffffffff, AM335X_TIMEOUT_MSEC))
+		return -1;
+
+	// Check to ensure that there was not any errors
+	if (read32(&reg->stat) & STAT_ERRI) {
+		printk(BIOS_WARNING, "AM335X MMC: Error while reading %08x\n",
+		       read32(&reg->stat));
+
+		// Clear the errors
+		write32(&reg->stat, STAT_ERROR_MASK);
+		return 1;
+	}
+
+	if (cmd->resp_type == CARD_RSP_R1b) {
+		if (am335x_wait_for_reg(&reg->stat, IE_TC, AM335X_TIMEOUT_MSEC))
+			return -1;
+
+		write32(&reg->stat, IE_TC);
+	}
+
+	write32(&reg->stat, IE_CC);
+
+	switch (cmd->resp_type) {
+	case CARD_RSP_R1:
+	case CARD_RSP_R1b:
+	case CARD_RSP_R3:
+		cmd->response[0] = read32(&reg->rsp10);
+		break;
+	case CARD_RSP_R2:
+		cmd->response[3] = read32(&reg->rsp10);
+		cmd->response[2] = read32(&reg->rsp32);
+		cmd->response[1] = read32(&reg->rsp54);
+		cmd->response[0] = read32(&reg->rsp76);
+		break;
+	case CARD_RSP_NONE:
+		break;
+	}
+
+	if (data != NULL && data->flags & DATA_FLAG_READ) {
+		if (am335x_wait_for_reg(&reg->stat, IE_BRR, AM335X_TIMEOUT_MSEC))
+			return -1;
+
+		uint32_t *dest32 = (uint32_t *)data->dest;
+
+		for (int count = 0; count < data->blocksize; count += 4) {
+			*dest32 = read32(&reg->data);
+			dest32++;
+		}
+
+		write32(&reg->stat, IE_TC);
+		write32(&reg->stat, IE_BRR);
+		clrbits32(&reg->ie, IE_BRR);
+	}
+
+	return 0;
+}
+
+static void set_ios(struct sd_mmc_ctrlr *ctrlr)
+{
+	struct am335x_mmc_host *mmc;
+	struct am335x_mmc *reg;
+
+	mmc = container_of(ctrlr, struct am335x_mmc_host, sd_mmc_ctrlr);
+	reg = mmc->reg;
+
+	if (ctrlr->request_hz != ctrlr->bus_hz) {
+		uint32_t requested_hz = ctrlr->request_hz;
+
+		requested_hz = MIN(requested_hz, ctrlr->f_min);
+		requested_hz = MAX(requested_hz, ctrlr->f_max);
+
+		uint32_t divisor = mmc->sd_clock_hz / requested_hz;
+		uint32_t actual = mmc->sd_clock_hz * divisor;
+
+		if (actual != ctrlr->bus_hz) {
+			clrbits32(&reg->sysctl, SYSCTL_CEN);
+
+			uint32_t new_sysctl = read32(&reg->sysctl);
+			new_sysctl &= ~(0x3ff << 6);
+			new_sysctl |= ((divisor & 0x3ff) << 6);
+
+			write32(&reg->sysctl, new_sysctl);
+
+			// Wait for clock stability
+			am335x_wait_for_reg(&reg->sysctl, SYSCTL_ICS, AM335X_TIMEOUT_MSEC);
+
+			setbits32(&reg->sysctl, SYSCTL_CEN);
+
+			ctrlr->bus_hz = mmc->sd_clock_hz / divisor;
+		}
+	}
+}
+
+int am335x_mmc_init_storage(struct am335x_mmc_host *mmc_host)
+{
+	int err = 0;
+
+	struct sd_mmc_ctrlr *mmc_ctrlr = &mmc_host->sd_mmc_ctrlr;
+	memset(mmc_ctrlr, 0, sizeof(mmc_ctrlr));
+
+
+	err = am335x_mmc_init(mmc_host->reg);
+	if (err != 0) {
+		printk(BIOS_ERR, "ERROR: Initialising AM335X SD failed.\n");
+		return err;
+	}
+
+	mmc_ctrlr->send_cmd = &am335x_send_cmd;
+	mmc_ctrlr->set_ios = &set_ios;
+
+	mmc_ctrlr->voltages = MMC_VDD_30_31;
+	mmc_ctrlr->b_max = 1;
+	mmc_ctrlr->bus_width = 1;
+	mmc_ctrlr->f_max = 48000000;
+	mmc_ctrlr->f_min = 400000;
+	mmc_ctrlr->bus_hz = 400000;
+
+	return 0;
+}
diff --git a/src/soc/ti/am335x/mmc.h b/src/soc/ti/am335x/mmc.h
new file mode 100644
index 0000000..757795d
--- /dev/null
+++ b/src/soc/ti/am335x/mmc.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef AM335X_MMC_H
+#define AM335X_MMC_H
+
+#include <inttypes.h>
+#include <commonlib/sd_mmc_ctrlr.h>
+
+#define MMCHS0_BASE 0x48060000
+
+struct am335x_mmc {
+	uint8_t res1[0x110];
+	uint32_t sysconfig;
+	uint32_t sysstatus;
+	uint8_t res2[0x14];
+	uint32_t con;
+	uint32_t pwcnt;
+	uint32_t dll;
+	uint8_t res3[0xcc];
+	uint32_t blk;
+	uint32_t arg;
+	uint32_t cmd;
+	uint32_t rsp10;
+	uint32_t rsp32;
+	uint32_t rsp54;
+	uint32_t rsp76;
+	uint32_t data;
+	uint32_t pstate;
+	uint32_t hctl;
+	uint32_t sysctl;
+	uint32_t stat;
+	uint32_t ie;
+	uint8_t res4[0x4];
+	uint32_t ac12;
+	uint32_t capa;
+	uint32_t capa2;
+	uint8_t res5[0xc];
+	uint32_t admaes;
+	uint32_t admasal;
+} __packed;
+
+struct am335x_mmc_host {
+	struct sd_mmc_ctrlr sd_mmc_ctrlr;
+	struct am335x_mmc *reg;
+	uint32_t sd_clock_hz;
+};
+
+int am335x_mmc_init_storage(struct am335x_mmc_host *mmc_host);
+
+#endif