mpfs/mpfs_ddr.c: Stop the DDR training once it is completed

The DDR training IP stays active otherwise, so stop it when the training
is complete.

This fixes a potential interrupt storm via MPFS_IRQ_DDRC_TRAIN.

arch/risc-v/src/mpfs/mpfs_ddr.c

@@ -45,9 +45,11 @@
 
 #include "riscv_internal.h"
 #include "mpfs_dma.h"
+#include "mpfs_plic.h"
 #include "hardware/mpfs_sysreg.h"
 #include "hardware/mpfs_ddr.h"
 #include "hardware/mpfs_sgmii.h"
+#include "hardware/mpfs_plic.h"
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -3900,6 +3902,44 @@ static int mpfs_ddr_test_32bit_nc(struct mpfs_ddr_priv_s *priv)
   return 0;
 }
 
+/****************************************************************************
+ * Name: mpfs_training_stop
+ *
+ * Description:
+ *   This stops the DDR training process, resetting the training IP.
+ *
+ * Input Parameters:
+ *   priv    - Instance of the ddr private state structure
+ *
+ ****************************************************************************/
+
+static void mpfs_training_stop(struct mpfs_ddr_priv_s *priv)
+{
+  uintptr_t claim_address;
+  uint32_t irq;
+
+  /* Not needed for now */
+
+  UNUSED(priv);
+
+  /* Stop training, i.e. reset the training block */
+
+  putreg32(0, MPFS_DDR_CSR_APB_PHY_DFI_INIT_START);
+  putreg32(0x02, MPFS_CFG_DDR_SGMII_PHY_TRAINING_RESET);
+
+  /* Eat a way any lingering DDRC interrupt */
+
+  claim_address = mpfs_plic_get_claimbase();
+  irq = MPFS_IRQ_EXT_START + getreg32(claim_address);
+
+  if (irq == MPFS_IRQ_DDRC_TRAIN)
+    {
+      /* Claim this interrupt, clearing the source */
+
+      putreg32(irq - MPFS_IRQ_EXT_START, claim_address);
+    }
+}
+
 /****************************************************************************
  * Name: mpfs_ddr_setup
  *
@@ -4040,6 +4080,10 @@ static int mpfs_ddr_setup(struct mpfs_ddr_priv_s *priv)
 
   mpfs_setup_ddr_segments(LIBERO_SEG_SETUP);
 
+  /* Stop the training */
+
+  mpfs_training_stop(priv);
+
   return 0;
 }