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Message-Id: <20200611194833.2640177-2-elder@linaro.org>
Date: Thu, 11 Jun 2020 14:48:30 -0500
From: Alex Elder <elder@...aro.org>
To: davem@...emloft.net, kuba@...nel.org
Cc: evgreen@...omium.org, subashab@...eaurora.org,
cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net v2 1/4] net: ipa: program metadata mask differently
The way the mask value is programmed for QMAP RX endpoints was based
on some wrong assumptions about the way metadata containing the QMAP
mux_id value is formatted. The metadata value supplied by the
modem is *not* in QMAP format, and in fact contains the mux_id we
want in its (big endian) low-order byte. That byte must be written
by the IPA into offset 1 of the QMAP header it inserts before the
received packet.
QMAP TX endpoints *do* use a QMAP header as the metadata sent with
each packet. The modem assumes this, and based on that assumes the
mux_id is in the second byte. To match those assumptions we must
program the modem TX (QMAP) endpoint HDR register to indicate the
metadata will be found at offset 0 in the message header.
The previous configuration managed to work, but it was not working
correctly. This patch fixes a bug whose symptom was receipt of
messages containing the wrong QMAP mux_id.
In fixing this, get rid of ipa_rmnet_mux_id_metadata_mask(), which
was more or less defined so there was a separate place to explain
what was happening as we generated the mask value. Instead, put a
longer description of how this works above ipa_endpoint_init_hdr(),
and define the metadata mask to use as a simple constant.
Signed-off-by: Alex Elder <elder@...aro.org>
---
v2: Added back the static specifier to ipa_endpoint_init_hdr(),
as suggested by the kernel test robot <lkp@...el.com>.
drivers/net/ipa/ipa_endpoint.c | 72 ++++++++++++++++++----------------
1 file changed, 39 insertions(+), 33 deletions(-)
diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index 66649a806dd1..2825dca23ec4 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -32,6 +32,9 @@
/* The amount of RX buffer space consumed by standard skb overhead */
#define IPA_RX_BUFFER_OVERHEAD (PAGE_SIZE - SKB_MAX_ORDER(NET_SKB_PAD, 0))
+/* Where to find the QMAP mux_id for a packet within modem-supplied metadata */
+#define IPA_ENDPOINT_QMAP_METADATA_MASK 0x000000ff /* host byte order */
+
#define IPA_ENDPOINT_RESET_AGGR_RETRY_MAX 3
#define IPA_AGGR_TIME_LIMIT_DEFAULT 1000 /* microseconds */
@@ -433,6 +436,24 @@ static void ipa_endpoint_init_cfg(struct ipa_endpoint *endpoint)
iowrite32(val, endpoint->ipa->reg_virt + offset);
}
+/**
+ * We program QMAP endpoints so each packet received is preceded by a QMAP
+ * header structure. The QMAP header contains a 1-byte mux_id and 2-byte
+ * packet size field, and we have the IPA hardware populate both for each
+ * received packet. The header is configured (in the HDR_EXT register)
+ * to use big endian format.
+ *
+ * The packet size is written into the QMAP header's pkt_len field. That
+ * location is defined here using the HDR_OFST_PKT_SIZE field.
+ *
+ * The mux_id comes from a 4-byte metadata value supplied with each packet
+ * by the modem. It is *not* a QMAP header, but it does contain the mux_id
+ * value that we want, in its low-order byte. A bitmask defined in the
+ * endpoint's METADATA_MASK register defines which byte within the modem
+ * metadata contains the mux_id. And the OFST_METADATA field programmed
+ * here indicates where the extracted byte should be placed within the QMAP
+ * header.
+ */
static void ipa_endpoint_init_hdr(struct ipa_endpoint *endpoint)
{
u32 offset = IPA_REG_ENDP_INIT_HDR_N_OFFSET(endpoint->endpoint_id);
@@ -441,25 +462,31 @@ static void ipa_endpoint_init_hdr(struct ipa_endpoint *endpoint)
if (endpoint->data->qmap) {
size_t header_size = sizeof(struct rmnet_map_header);
+ /* We might supply a checksum header after the QMAP header */
if (endpoint->toward_ipa && endpoint->data->checksum)
header_size += sizeof(struct rmnet_map_ul_csum_header);
-
val |= u32_encode_bits(header_size, HDR_LEN_FMASK);
- /* metadata is the 4 byte rmnet_map header itself */
- val |= HDR_OFST_METADATA_VALID_FMASK;
- val |= u32_encode_bits(0, HDR_OFST_METADATA_FMASK);
- /* HDR_ADDITIONAL_CONST_LEN is 0; (IPA->AP only) */
+
+ /* Define how to fill mux_id in a received QMAP header */
if (!endpoint->toward_ipa) {
- u32 size_offset = offsetof(struct rmnet_map_header,
- pkt_len);
+ u32 off; /* Field offset within header */
+ /* Where IPA will write the metadata value */
+ off = offsetof(struct rmnet_map_header, mux_id);
+ val |= u32_encode_bits(off, HDR_OFST_METADATA_FMASK);
+
+ /* Where IPA will write the length */
+ off = offsetof(struct rmnet_map_header, pkt_len);
val |= HDR_OFST_PKT_SIZE_VALID_FMASK;
- val |= u32_encode_bits(size_offset,
- HDR_OFST_PKT_SIZE_FMASK);
+ val |= u32_encode_bits(off, HDR_OFST_PKT_SIZE_FMASK);
}
+ /* For QMAP TX, metadata offset is 0 (modem assumes this) */
+ val |= HDR_OFST_METADATA_VALID_FMASK;
+
+ /* HDR_ADDITIONAL_CONST_LEN is 0; (RX only) */
/* HDR_A5_MUX is 0 */
/* HDR_LEN_INC_DEAGG_HDR is 0 */
- /* HDR_METADATA_REG_VALID is 0; (AP->IPA only) */
+ /* HDR_METADATA_REG_VALID is 0 (TX only) */
}
iowrite32(val, endpoint->ipa->reg_virt + offset);
@@ -482,28 +509,6 @@ static void ipa_endpoint_init_hdr_ext(struct ipa_endpoint *endpoint)
iowrite32(val, endpoint->ipa->reg_virt + offset);
}
-/**
- * Generate a metadata mask value that will select only the mux_id
- * field in an rmnet_map header structure. The mux_id is at offset
- * 1 byte from the beginning of the structure, but the metadata
- * value is treated as a 4-byte unit. So this mask must be computed
- * with endianness in mind. Note that ipa_endpoint_init_hdr_metadata_mask()
- * will convert this value to the proper byte order.
- *
- * Marked __always_inline because this is really computing a
- * constant value.
- */
-static __always_inline __be32 ipa_rmnet_mux_id_metadata_mask(void)
-{
- size_t mux_id_offset = offsetof(struct rmnet_map_header, mux_id);
- u32 mux_id_mask = 0;
- u8 *bytes;
-
- bytes = (u8 *)&mux_id_mask;
- bytes[mux_id_offset] = 0xff; /* mux_id is 1 byte */
-
- return cpu_to_be32(mux_id_mask);
-}
static void ipa_endpoint_init_hdr_metadata_mask(struct ipa_endpoint *endpoint)
{
@@ -513,8 +518,9 @@ static void ipa_endpoint_init_hdr_metadata_mask(struct ipa_endpoint *endpoint)
offset = IPA_REG_ENDP_INIT_HDR_METADATA_MASK_N_OFFSET(endpoint_id);
+ /* Note that HDR_ENDIANNESS indicates big endian header fields */
if (!endpoint->toward_ipa && endpoint->data->qmap)
- val = ipa_rmnet_mux_id_metadata_mask();
+ val = cpu_to_be32(IPA_ENDPOINT_QMAP_METADATA_MASK);
iowrite32(val, endpoint->ipa->reg_virt + offset);
}
--
2.25.1
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