net: ipa: header pad field only valid for AP->modem endpoint

Only QMAP endpoints should be configured to find a pad size field
within packet headers.  They are found in the first byte of the QMAP
header (and the hardware fills only the 6 bits in that byte that
constitute the pad_len field).

The RMNet driver assumes the pad_len field is valid for received
packets, so we want to ensure the pad_len field is filled in that
case.  That driver also assumes the length in the QMAP header
includes the pad bytes.

The RMNet driver does *not* pad the packets it sends, so the pad_len
field can be ignored.

Fix ipa_endpoint_init_hdr_ext() so it only marks the pad field
offset valid for QMAP RX endpoints, and in that case indicates
that the length field in the header includes the pad bytes.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index bf3e8ce..9f50d0d 100644 (file)
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -467,7 +467,7 @@ static void ipa_endpoint_init_hdr(struct ipa_endpoint *endpoint)
                        header_size += sizeof(struct rmnet_map_ul_csum_header);
                val |= u32_encode_bits(header_size, HDR_LEN_FMASK);
 
-               /* Define how to fill mux_id in a received QMAP header */
+               /* Define how to fill fields in a received QMAP header */
                if (!endpoint->toward_ipa) {
                        u32 off;        /* Field offset within header */
 
@@ -499,10 +499,21 @@ static void ipa_endpoint_init_hdr_ext(struct ipa_endpoint *endpoint)
        u32 val = 0;
 
        val |= HDR_ENDIANNESS_FMASK;            /* big endian */
-       val |= HDR_TOTAL_LEN_OR_PAD_VALID_FMASK;
-       /* HDR_TOTAL_LEN_OR_PAD is 0 (pad, not total_len) */
+
+       /* A QMAP header contains a 6 bit pad field at offset 0.  The RMNet
+        * driver assumes this field is meaningful in packets it receives,
+        * and assumes the header's payload length includes that padding.
+        * The RMNet driver does *not* pad packets it sends, however, so
+        * the pad field (although 0) should be ignored.
+        */
+       if (endpoint->data->qmap && !endpoint->toward_ipa) {
+               val |= HDR_TOTAL_LEN_OR_PAD_VALID_FMASK;
+               /* HDR_TOTAL_LEN_OR_PAD is 0 (pad, not total_len) */
+               val |= HDR_PAYLOAD_LEN_INC_PADDING_FMASK;
+               /* HDR_TOTAL_LEN_OR_PAD_OFFSET is 0 */
+       }
+
        /* HDR_PAYLOAD_LEN_INC_PADDING is 0 */
-       /* HDR_TOTAL_LEN_OR_PAD_OFFSET is 0 */
        if (!endpoint->toward_ipa)
                val |= u32_encode_bits(pad_align, HDR_PAD_TO_ALIGNMENT_FMASK);