netdev - [PATCH net-next 3/7] net: ipa: ignore endianness if there is no header

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Date:   Thu, 19 May 2022 10:12:13 -0500
From:   Alex Elder <elder@...aro.org>
To:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Cc:     mka@...omium.org, evgreen@...omium.org, bjorn.andersson@...aro.org,
        quic_cpratapa@...cinc.com, quic_avuyyuru@...cinc.com,
        quic_jponduru@...cinc.com, quic_subashab@...cinc.com,
        elder@...nel.org, netdev@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next 3/7] net: ipa: ignore endianness if there is no header

If we program an RX endpoint to have no header (header length is 0),
header-related endpoint configuration values are meaningless and are
ignored.

The only case we support that defines a header is QMAP endpoints.
In ipa_endpoint_init_hdr_ext() we set the endianness mask value
unconditionally, but it should not be done if there is no header
(meaning it is not configured for QMAP).

Set the endianness conditionally, and rearrange the logic in that
function slightly to avoid testing the qmap flag twice.

Delete an incorrect comment in ipa_endpoint_init_aggr().

Signed-off-by: Alex Elder <elder@...aro.org>
---
 drivers/net/ipa/ipa_endpoint.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index e133eb2bebcfb..3fcd7c64c9bba 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -587,19 +587,23 @@ static void ipa_endpoint_init_hdr_ext(struct ipa_endpoint *endpoint)
 	struct ipa *ipa = endpoint->ipa;
 	u32 val = 0;
 
-	val |= HDR_ENDIANNESS_FMASK;		/* big endian */
+	if (endpoint->data->qmap) {
+		/* We have a header, so we must specify its endianness */
+		val |= HDR_ENDIANNESS_FMASK;	/* big endian */
 
-	/* 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 */
+		/* 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->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 */
@@ -759,8 +763,6 @@ static void ipa_endpoint_init_aggr(struct ipa_endpoint *endpoint)
 
 			close_eof = rx_data->aggr_close_eof;
 			val |= aggr_sw_eof_active_encoded(version, close_eof);
-
-			/* AGGR_HARD_BYTE_LIMIT_ENABLE is 0 */
 		} else {
 			val |= u32_encode_bits(IPA_ENABLE_DEAGGR,
 					       AGGR_EN_FMASK);
-- 
2.32.0