AM6442: How does EMMC warm reset take effect

Hello,

The following patch on top of the latest SDK (v11.2) exposes the API "MMCSD_enableRstN" to enable the hardware reset functionality.

diff --git a/source/drivers/mmcsd/v0/lld/mmcsd_lld.h b/source/drivers/mmcsd/v0/lld/mmcsd_lld.h
index 068cbc97c30..d0bac37c925 100644
--- a/source/drivers/mmcsd/v0/lld/mmcsd_lld.h
+++ b/source/drivers/mmcsd/v0/lld/mmcsd_lld.h
@@ -647,6 +647,19 @@ int32_t MMCSD_lld_enableBootPartition(MMCSDLLD_Handle handle,
  */
 int32_t MMCSD_lld_disableBootPartition(MMCSDLLD_Handle handle);
 
+/**
+ *  \brief  This function enables the RST_N signal for eMMC device.
+ *
+ *  \pre    MMCSD controller has been initialized using #MMCSD_lld_init().
+ *
+ *  \param  handle         [IN] Handle to the MMCSD instance used.
+ *
+ *  \return #MMCSD_STS_SUCCESS on success; else error on failure.
+ *
+ *  \sa     #MMCSD_lld_init()
+ */
+int32_t MMCSD_lld_enableRstN(MMCSDLLD_Handle handle);
+
 /* ========================================================================== */
 /*                        ISR Function Declarations                           */
 /* ========================================================================== */
diff --git a/source/drivers/mmcsd/v0/lld/mmcsd_v0_lld.c b/source/drivers/mmcsd/v0/lld/mmcsd_v0_lld.c
index b50bf9adcc6..d5b9f6bb9d7 100644
--- a/source/drivers/mmcsd/v0/lld/mmcsd_v0_lld.c
+++ b/source/drivers/mmcsd/v0/lld/mmcsd_v0_lld.c
@@ -173,6 +173,14 @@ Bit     Device Type
 /** \brief Macros for ECSD Register Indexes */
 #define MMCSD_ECSD_BUS_WIDTH_INDEX                      ((uint32_t) 183U)
 #define MMCSD_ECSD_HS_TIMING_INDEX                      ((uint32_t) 185U)
+#define MMCSD_ECSD_RST_N_FUNCTION_INDEX                 ((uint32_t) 162U)
+
+/** \brief Macros for RST_n_FUNCTION values (7.4.42 RST_n_FUNCTION [162])
+ *  JEDEC Standard No. 84-B51
+ */
+#define MMCSD_ECSD_RST_N_FUNCTION_TEMP_DISABLED         ((uint32_t) 0x00U)
+#define MMCSD_ECSD_RST_N_FUNCTION_PERMANENTLY_ENABLED   ((uint32_t) 0x01U)
+#define MMCSD_ECSD_RST_N_FUNCTION_PERMANENTLY_DISABLED  ((uint32_t) 0x02U)
 
 /** \brief Macros for States Used during the Initialization of SD Device */
 #define MMCSD_SD_INIT_STATE_CONTROLLER_INIT                 ((uint32_t) 0U)
@@ -1496,6 +1504,50 @@ int32_t MMCSD_lld_disableBootPartition(MMCSDLLD_Handle handle)
     return status;
 }
 
+int32_t MMCSD_lld_enableRstN(MMCSDLLD_Handle handle)
+{
+    int32_t status = MMCSD_STS_SUCCESS;
+    MMCSDLLD_Object *object = (MMCSDLLD_Object *)handle;
+    MMCSDLLD_Transaction trans;
+
+    if(object != NULL_PTR)
+    {
+        /* Check if card type is eMMC */
+        if(object->initHandle->cardType == MMCSD_CARD_TYPE_EMMC)
+        {
+            uint32_t arg;
+
+            /* Configure the ECSD register RST_n_FUNCTION to permanently enable
+             * using CMD6 (SWITCH command)
+             * Argument format: [31:26]=0 [25:24]=Access [23:16]=Index [15:8]=Value [7:0]=CmdSet
+             */
+            arg = (uint32_t)((MMCSD_CMD6_ACCESS_MASK_WRITE_BYTE << 24U)        |
+                            (MMCSD_ECSD_RST_N_FUNCTION_INDEX << 16U)           |
+                            (MMCSD_ECSD_RST_N_FUNCTION_PERMANENTLY_ENABLED << 8U));
+
+            /* Send CMD6 to enable RST_N */
+            MMCSD_lld_initTransaction(&trans);
+            trans.cmd = MMCSD_MMC_CMD(6U);
+            trans.arg = arg;
+            status = MMCSD_lld_transferPoll(handle, &trans);
+
+            /* Delay for 5 ms for the change to take effect in the device */
+            ClockP_usleep(5000);
+        }
+        else
+        {
+            /* RST_N is only applicable for eMMC devices */
+            status = MMCSD_STS_ERR;
+        }
+    }
+    else
+    {
+        status = MMCSD_STS_ERR_INVALID_PARAM;
+    }
+
+    return status;
+}
+
 /* ========================================================================== */
 /*                     API ISR Function Definitions                           */
 /* ========================================================================== */
diff --git a/source/drivers/mmcsd/v0/mmcsd.h b/source/drivers/mmcsd/v0/mmcsd.h
index 4314ed06fc6..c543a184425 100644
--- a/source/drivers/mmcsd/v0/mmcsd.h
+++ b/source/drivers/mmcsd/v0/mmcsd.h
@@ -418,6 +418,20 @@ int32_t MMCSD_enableBootPartition(MMCSD_Handle handle, uint32_t partitionNum);
  */
 int32_t MMCSD_disableBootPartition(MMCSD_Handle handle);
 
+/**
+ *  \brief  This function enables the RST_N signal for eMMC device
+ *
+ *  \pre    MMCSD controller has been opened using #MMCSD_open()
+ *
+ *  \param  handle         #MMCSD_Handle returned from #MMCSD_open()
+ *
+ *  \return #SystemP_SUCCESS on successful enable; else error on failure
+ *
+ *  \sa     #MMCSD_init()
+ *  \sa     #MMCSD_open()
+ */
+int32_t MMCSD_enableRstN(MMCSD_Handle handle);
+
 /** @} */
 
 #ifdef __cplusplus
diff --git a/source/drivers/mmcsd/v0/mmcsd_v0.c b/source/drivers/mmcsd/v0/mmcsd_v0.c
index 40a98a821ff..cc43073d832 100644
--- a/source/drivers/mmcsd/v0/mmcsd_v0.c
+++ b/source/drivers/mmcsd/v0/mmcsd_v0.c
@@ -658,6 +658,28 @@ int32_t MMCSD_disableBootPartition(MMCSD_Handle handle)
     return status;
 }
 
+int32_t MMCSD_enableRstN(MMCSD_Handle handle)
+{
+    int32_t status = SystemP_SUCCESS;
+    MMCSD_Object *object = ((MMCSD_Config *)handle)->object;
+    MMCSDLLD_Handle mmcsdLldHandle = object->mmcsdLldHandle;
+
+    status = SemaphoreP_pend(&object->mutex, SystemP_WAIT_FOREVER);
+
+    if(status == SystemP_SUCCESS)
+    {
+        /* Call LLD function to enable RST_N */
+        status = MMCSD_lld_enableRstN(mmcsdLldHandle);
+        (void)SemaphoreP_post(&object->mutex);
+    }
+    else
+    {
+        /* Mutex not Available */
+    }
+
+    return status;
+}
+
 /* ========================================================================== */
 /*                       ISR Function Definitions                             */
 /* ========================================================================== */

This API can be called from any application that has eMMC enabled in the Sysconfig like MMCSD_RAW_IO example. Please note this is a one time operation only. Once the functionality is enabled successfully, it does not need to be done again.

I only had an EVM with this already enabled so I did not have a way to test the implemented code. Hopefully, it works.