crypto: octeontx2 - add synchronization between mailbox accesses

Since there are two workqueues implemented in CPTPF driver - one
for handling mailbox requests from VFs and another for handling FLR.
In both cases PF driver will forward the request to AF driver by
writing to mailbox memory. A race condition may arise if two
simultaneous requests are written to mailbox memory. Introducing
locking mechanism to maintain synchronization between multiple
mailbox accesses.
Signed-off-by: Harman Kalra <hkalra@marvell.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/marvell/octeontx2/otx2_cpt_common.h

@@ -157,5 +157,6 @@ struct otx2_cptlfs_info;
 int otx2_cpt_attach_rscrs_msg(struct otx2_cptlfs_info *lfs);
 int otx2_cpt_detach_rsrcs_msg(struct otx2_cptlfs_info *lfs);
 int otx2_cpt_msix_offset_msg(struct otx2_cptlfs_info *lfs);
+int otx2_cpt_sync_mbox_msg(struct otx2_mbox *mbox);
 
 #endif /* __OTX2_CPT_COMMON_H */

drivers/crypto/marvell/octeontx2/otx2_cpt_mbox_common.c

@@ -202,3 +202,17 @@ int otx2_cpt_msix_offset_msg(struct otx2_cptlfs_info *lfs)
 	}
 	return ret;
 }
+
+int otx2_cpt_sync_mbox_msg(struct otx2_mbox *mbox)
+{
+	int err;
+
+	if (!otx2_mbox_nonempty(mbox, 0))
+		return 0;
+	otx2_mbox_msg_send(mbox, 0);
+	err = otx2_mbox_wait_for_rsp(mbox, 0);
+	if (err)
+		return err;
+
+	return otx2_mbox_check_rsp_msgs(mbox, 0);
+}

drivers/crypto/marvell/octeontx2/otx2_cptpf.h

@@ -46,6 +46,7 @@ struct otx2_cptpf_dev {
 
 	struct workqueue_struct	*flr_wq;
 	struct cptpf_flr_work   *flr_work;
+	struct mutex            lock;   /* serialize mailbox access */
 
 	unsigned long cap_flag;
 	u8 pf_id;               /* RVU PF number */

drivers/crypto/marvell/octeontx2/otx2_cptpf_main.c

@@ -140,6 +140,7 @@ static void cptpf_flr_wq_handler(struct work_struct *work)
 
 	vf = flr_work - pf->flr_work;
 
+	mutex_lock(&pf->lock);
 	req = otx2_mbox_alloc_msg_rsp(mbox, 0, sizeof(*req),
 				      sizeof(struct msg_rsp));
 	if (!req)
@@ -151,16 +152,19 @@ static void cptpf_flr_wq_handler(struct work_struct *work)
 	req->pcifunc |= (vf + 1) & RVU_PFVF_FUNC_MASK;
 
 	otx2_cpt_send_mbox_msg(mbox, pf->pdev);
+	if (!otx2_cpt_sync_mbox_msg(&pf->afpf_mbox)) {
 
-	if (vf >= 64) {
-		reg = 1;
-		vf = vf - 64;
+		if (vf >= 64) {
+			reg = 1;
+			vf = vf - 64;
+		}
+		/* Clear transaction pending register */
+		otx2_cpt_write64(pf->reg_base, BLKADDR_RVUM, 0,
+				 RVU_PF_VFTRPENDX(reg), BIT_ULL(vf));
+		otx2_cpt_write64(pf->reg_base, BLKADDR_RVUM, 0,
+				 RVU_PF_VFFLR_INT_ENA_W1SX(reg), BIT_ULL(vf));
 	}
-	/* Clear transaction pending register */
-	otx2_cpt_write64(pf->reg_base, BLKADDR_RVUM, 0,
-			 RVU_PF_VFTRPENDX(reg), BIT_ULL(vf));
-	otx2_cpt_write64(pf->reg_base, BLKADDR_RVUM, 0,
-			 RVU_PF_VFFLR_INT_ENA_W1SX(reg), BIT_ULL(vf));
+	mutex_unlock(&pf->lock);
 }
 
 static irqreturn_t cptpf_vf_flr_intr(int __always_unused irq, void *arg)
@@ -468,6 +472,7 @@ static int cptpf_afpf_mbox_init(struct otx2_cptpf_dev *cptpf)
 		goto error;
 
 	INIT_WORK(&cptpf->afpf_mbox_work, otx2_cptpf_afpf_mbox_handler);
+	mutex_init(&cptpf->lock);
 	return 0;
 
 error:

drivers/crypto/marvell/octeontx2/otx2_cptpf_mbox.c

@@ -18,6 +18,7 @@ static int forward_to_af(struct otx2_cptpf_dev *cptpf,
 	struct mbox_msghdr *msg;
 	int ret;
 
+	mutex_lock(&cptpf->lock);
 	msg = otx2_mbox_alloc_msg(&cptpf->afpf_mbox, 0, size);
 	if (msg == NULL)
 		return -ENOMEM;
@@ -29,15 +30,19 @@ static int forward_to_af(struct otx2_cptpf_dev *cptpf,
 	msg->sig = req->sig;
 	msg->ver = req->ver;
 
-	otx2_mbox_msg_send(&cptpf->afpf_mbox, 0);
-	ret = otx2_mbox_wait_for_rsp(&cptpf->afpf_mbox, 0);
+	ret = otx2_cpt_sync_mbox_msg(&cptpf->afpf_mbox);
+	/* Error code -EIO indicate there is a communication failure
+	 * to the AF. Rest of the error codes indicate that AF processed
+	 * VF messages and set the error codes in response messages
+	 * (if any) so simply forward responses to VF.
+	 */
 	if (ret == -EIO) {
-		dev_err(&cptpf->pdev->dev, "RVU MBOX timeout.\n");
+		dev_warn(&cptpf->pdev->dev,
+			 "AF not responding to VF%d messages\n", vf->vf_id);
+		mutex_unlock(&cptpf->lock);
 		return ret;
-	} else if (ret) {
-		dev_err(&cptpf->pdev->dev, "RVU MBOX error: %d.\n", ret);
-		return -EFAULT;
 	}
+	mutex_unlock(&cptpf->lock);
 	return 0;
 }
 
@@ -204,6 +209,10 @@ void otx2_cptpf_vfpf_mbox_handler(struct work_struct *work)
 		if (err == -ENOMEM || err == -EIO)
 			break;
 		offset = msg->next_msgoff;
+		/* Write barrier required for VF responses which are handled by
+		 * PF driver and not forwarded to AF.
+		 */
+		smp_wmb();
 	}
 	/* Send mbox responses to VF */
 	if (mdev->num_msgs)
@@ -350,6 +359,8 @@ void otx2_cptpf_afpf_mbox_handler(struct work_struct *work)
 			process_afpf_mbox_msg(cptpf, msg);
 
 		offset = msg->next_msgoff;
+		/* Sync VF response ready to be sent */
+		smp_wmb();
 		mdev->msgs_acked++;
 	}
 	otx2_mbox_reset(afpf_mbox, 0);