octeontx2-af: Secure APR table update with the lock

APR table contains the lmtst base address of PF/VFs. These entries
are updated by the PF/VF during the device probe. The lmtst address
is fetched from HW using "TXN_REQ" and "ADDR_RSP_STS" registers.
The lock tries to protect these registers from getting overwritten
when multiple PFs invokes rvu_get_lmtaddr() simultaneously.

For example, if PF1 submit the request and got permitted before it
reads the response and PF2 got scheduled submit the request then the
response of PF1 is overwritten by the PF2 response.

Fixes: 893ae972 ("octeontx2-af: cn10k: Support configurable LMTST regions")
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeontx2/af/rvu_cn10k.c

@@ -60,13 +60,14 @@ static int rvu_get_lmtaddr(struct rvu *rvu, u16 pcifunc,
 			   u64 iova, u64 *lmt_addr)
 {
 	u64 pa, val, pf;
-	int err;
+	int err = 0;
 
 	if (!iova) {
 		dev_err(rvu->dev, "%s Requested Null address for transulation\n", __func__);
 		return -EINVAL;
 	}
 
+	mutex_lock(&rvu->rsrc_lock);
 	rvu_write64(rvu, BLKADDR_RVUM, RVU_AF_SMMU_ADDR_REQ, iova);
 	pf = rvu_get_pf(pcifunc) & 0x1F;
 	val = BIT_ULL(63) | BIT_ULL(14) | BIT_ULL(13) | pf << 8 |
@@ -76,12 +77,13 @@ static int rvu_get_lmtaddr(struct rvu *rvu, u16 pcifunc,
 	err = rvu_poll_reg(rvu, BLKADDR_RVUM, RVU_AF_SMMU_ADDR_RSP_STS, BIT_ULL(0), false);
 	if (err) {
 		dev_err(rvu->dev, "%s LMTLINE iova transulation failed\n", __func__);
-		return err;
+		goto exit;
 	}
 	val = rvu_read64(rvu, BLKADDR_RVUM, RVU_AF_SMMU_ADDR_RSP_STS);
 	if (val & ~0x1ULL) {
 		dev_err(rvu->dev, "%s LMTLINE iova transulation failed err:%llx\n", __func__, val);
-		return -EIO;
+		err = -EIO;
+		goto exit;
 	}
 	/* PA[51:12] = RVU_AF_SMMU_TLN_FLIT0[57:18]
 	 * PA[11:0] = IOVA[11:0]
@@ -89,8 +91,9 @@ static int rvu_get_lmtaddr(struct rvu *rvu, u16 pcifunc,
 	pa = rvu_read64(rvu, BLKADDR_RVUM, RVU_AF_SMMU_TLN_FLIT0) >> 18;
 	pa &= GENMASK_ULL(39, 0);
 	*lmt_addr = (pa << 12) | (iova  & 0xFFF);
-
-	return 0;
+exit:
+	mutex_unlock(&rvu->rsrc_lock);
+	return err;
 }
 
 static int rvu_update_lmtaddr(struct rvu *rvu, u16 pcifunc, u64 lmt_addr)