sata_nv: cleanup CPB and APRD initialization

Clean up the initialization of the CPB and APRD structures so that we
strictly follow the rules for ordering of writes to the CPB flags and
response flags, and prevent duplicate initialization.
Signed-off-by: NRobert Hancock <hancockr@shaw.ca>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/ata/sata_nv.c

@@ -1164,11 +1164,7 @@ static void nv_adma_fill_aprd(struct ata_queued_cmd *qc,
 			      int idx,
 			      struct nv_adma_prd *aprd)
 {
-	u8 flags;
-
-	memset(aprd, 0, sizeof(struct nv_adma_prd));
-
-	flags = 0;
+	u8 flags = 0;
 	if (qc->tf.flags & ATA_TFLAG_WRITE)
 		flags |= NV_APRD_WRITE;
 	if (idx == qc->n_elem - 1)
@@ -1179,6 +1175,7 @@ static void nv_adma_fill_aprd(struct ata_queued_cmd *qc,
 	aprd->addr  = cpu_to_le64(((u64)sg_dma_address(sg)));
 	aprd->len   = cpu_to_le32(((u32)sg_dma_len(sg))); /* len in bytes */
 	aprd->flags = flags;
+	aprd->packet_len = 0;
 }
 
 static void nv_adma_fill_sg(struct ata_queued_cmd *qc, struct nv_adma_cpb *cpb)
@@ -1199,6 +1196,8 @@ static void nv_adma_fill_sg(struct ata_queued_cmd *qc, struct nv_adma_cpb *cpb)
 	}
 	if (idx > 5)
 		cpb->next_aprd = cpu_to_le64(((u64)(pp->aprd_dma + NV_ADMA_SGTBL_SZ * qc->tag)));
+	else
+		cpb->next_aprd = cpu_to_le64(0);
 }
 
 static int nv_adma_use_reg_mode(struct ata_queued_cmd *qc)
@@ -1231,7 +1230,10 @@ static void nv_adma_qc_prep(struct ata_queued_cmd *qc)
 		return;
 	}
 
-	memset(cpb, 0, sizeof(struct nv_adma_cpb));
+	cpb->resp_flags = NV_CPB_RESP_DONE;
+	wmb();
+	cpb->ctl_flags = 0;
+	wmb();
 
 	cpb->len		= 3;
 	cpb->tag		= qc->tag;
@@ -1255,6 +1257,8 @@ static void nv_adma_qc_prep(struct ata_queued_cmd *qc)
 	   finished filling in all of the contents */
 	wmb();
 	cpb->ctl_flags = ctl_flags;
+	wmb();
+	cpb->resp_flags = 0;
 }
 
 static unsigned int nv_adma_qc_issue(struct ata_queued_cmd *qc)