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Date:   Mon, 3 Aug 2020 21:33:20 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: [PATCH v3 net-next 03/11] sfc_ef100: read Design Parameters at probe
 time

Several parts of the EF100 architecture are parameterised (to allow
 varying capabilities on FPGAs according to resource constraints), and
 these parameters are exposed to the driver through a TLV-encoded
 region of the BAR.
For the most part we either don't care about these values at all or
 just need to sanity-check them against the driver's assumptions, but
 there are a number of TSO limits which we record so that we will be
 able to check against them in the TX path when handling GSO skbs.

Signed-off-by: Edward Cree <ecree@...arflare.com>
---
 drivers/net/ethernet/sfc/ef100_nic.c | 216 +++++++++++++++++++++++++++
 drivers/net/ethernet/sfc/ef100_nic.h |   4 +
 2 files changed, 220 insertions(+)

diff --git a/drivers/net/ethernet/sfc/ef100_nic.c b/drivers/net/ethernet/sfc/ef100_nic.c
index c2bec2bdbc1f..9b5e4b42fe51 100644
--- a/drivers/net/ethernet/sfc/ef100_nic.c
+++ b/drivers/net/ethernet/sfc/ef100_nic.c
@@ -515,6 +515,208 @@ static int compare_versions(const char *a, const char *b)
 	return a_patch - b_patch;
 }
 
+enum ef100_tlv_state_machine {
+	EF100_TLV_TYPE,
+	EF100_TLV_TYPE_CONT,
+	EF100_TLV_LENGTH,
+	EF100_TLV_VALUE
+};
+
+struct ef100_tlv_state {
+	enum ef100_tlv_state_machine state;
+	u64 value;
+	u32 value_offset;
+	u16 type;
+	u8 len;
+};
+
+static int ef100_tlv_feed(struct ef100_tlv_state *state, u8 byte)
+{
+	switch (state->state) {
+	case EF100_TLV_TYPE:
+		state->type = byte & 0x7f;
+		state->state = (byte & 0x80) ? EF100_TLV_TYPE_CONT
+					     : EF100_TLV_LENGTH;
+		/* Clear ready to read in a new entry */
+		state->value = 0;
+		state->value_offset = 0;
+		return 0;
+	case EF100_TLV_TYPE_CONT:
+		state->type |= byte << 7;
+		state->state = EF100_TLV_LENGTH;
+		return 0;
+	case EF100_TLV_LENGTH:
+		state->len = byte;
+		/* We only handle TLVs that fit in a u64 */
+		if (state->len > sizeof(state->value))
+			return -EOPNOTSUPP;
+		/* len may be zero, implying a value of zero */
+		state->state = state->len ? EF100_TLV_VALUE : EF100_TLV_TYPE;
+		return 0;
+	case EF100_TLV_VALUE:
+		state->value |= ((u64)byte) << (state->value_offset * 8);
+		state->value_offset++;
+		if (state->value_offset >= state->len)
+			state->state = EF100_TLV_TYPE;
+		return 0;
+	default: /* state machine error, can't happen */
+		WARN_ON_ONCE(1);
+		return -EIO;
+	}
+}
+
+static int ef100_process_design_param(struct efx_nic *efx,
+				      const struct ef100_tlv_state *reader)
+{
+	struct ef100_nic_data *nic_data = efx->nic_data;
+
+	switch (reader->type) {
+	case ESE_EF100_DP_GZ_PAD: /* padding, skip it */
+		return 0;
+	case ESE_EF100_DP_GZ_PARTIAL_TSTAMP_SUB_NANO_BITS:
+		/* Driver doesn't support timestamping yet, so we don't care */
+		return 0;
+	case ESE_EF100_DP_GZ_EVQ_UNSOL_CREDIT_SEQ_BITS:
+		/* Driver doesn't support unsolicited-event credits yet, so
+		 * we don't care
+		 */
+		return 0;
+	case ESE_EF100_DP_GZ_NMMU_GROUP_SIZE:
+		/* Driver doesn't manage the NMMU (so we don't care) */
+		return 0;
+	case ESE_EF100_DP_GZ_RX_L4_CSUM_PROTOCOLS:
+		/* Driver uses CHECKSUM_COMPLETE, so we don't care about
+		 * protocol checksum validation
+		 */
+		return 0;
+	case ESE_EF100_DP_GZ_TSO_MAX_HDR_LEN:
+		nic_data->tso_max_hdr_len = min_t(u64, reader->value, 0xffff);
+		return 0;
+	case ESE_EF100_DP_GZ_TSO_MAX_HDR_NUM_SEGS:
+		/* We always put HDR_NUM_SEGS=1 in our TSO descriptors */
+		if (!reader->value) {
+			netif_err(efx, probe, efx->net_dev,
+				  "TSO_MAX_HDR_NUM_SEGS < 1\n");
+			return -EOPNOTSUPP;
+		}
+		return 0;
+	case ESE_EF100_DP_GZ_RXQ_SIZE_GRANULARITY:
+	case ESE_EF100_DP_GZ_TXQ_SIZE_GRANULARITY:
+		/* Our TXQ and RXQ sizes are always power-of-two and thus divisible by
+		 * EFX_MIN_DMAQ_SIZE, so we just need to check that
+		 * EFX_MIN_DMAQ_SIZE is divisible by GRANULARITY.
+		 * This is very unlikely to fail.
+		 */
+		if (EFX_MIN_DMAQ_SIZE % reader->value) {
+			netif_err(efx, probe, efx->net_dev,
+				  "%s size granularity is %llu, can't guarantee safety\n",
+				  reader->type == ESE_EF100_DP_GZ_RXQ_SIZE_GRANULARITY ? "RXQ" : "TXQ",
+				  reader->value);
+			return -EOPNOTSUPP;
+		}
+		return 0;
+	case ESE_EF100_DP_GZ_TSO_MAX_PAYLOAD_LEN:
+		nic_data->tso_max_payload_len = min_t(u64, reader->value, GSO_MAX_SIZE);
+		efx->net_dev->gso_max_size = nic_data->tso_max_payload_len;
+		return 0;
+	case ESE_EF100_DP_GZ_TSO_MAX_PAYLOAD_NUM_SEGS:
+		nic_data->tso_max_payload_num_segs = min_t(u64, reader->value, 0xffff);
+		efx->net_dev->gso_max_segs = nic_data->tso_max_payload_num_segs;
+		return 0;
+	case ESE_EF100_DP_GZ_TSO_MAX_NUM_FRAMES:
+		nic_data->tso_max_frames = min_t(u64, reader->value, 0xffff);
+		return 0;
+	case ESE_EF100_DP_GZ_COMPAT:
+		if (reader->value) {
+			netif_err(efx, probe, efx->net_dev,
+				  "DP_COMPAT has unknown bits %#llx, driver not compatible with this hw\n",
+				  reader->value);
+			return -EOPNOTSUPP;
+		}
+		return 0;
+	case ESE_EF100_DP_GZ_MEM2MEM_MAX_LEN:
+		/* Driver doesn't use mem2mem transfers */
+		return 0;
+	case ESE_EF100_DP_GZ_EVQ_TIMER_TICK_NANOS:
+		/* Driver doesn't currently use EVQ_TIMER */
+		return 0;
+	case ESE_EF100_DP_GZ_NMMU_PAGE_SIZES:
+		/* Driver doesn't manage the NMMU (so we don't care) */
+		return 0;
+	case ESE_EF100_DP_GZ_VI_STRIDES:
+		/* We never try to set the VI stride, and we don't rely on
+		 * being able to find VIs past VI 0 until after we've learned
+		 * the current stride from MC_CMD_GET_CAPABILITIES.
+		 * So the value of this shouldn't matter.
+		 */
+		if (reader->value != ESE_EF100_DP_GZ_VI_STRIDES_DEFAULT)
+			netif_dbg(efx, probe, efx->net_dev,
+				  "NIC has other than default VI_STRIDES (mask "
+				  "%#llx), early probing might use wrong one\n",
+				  reader->value);
+		return 0;
+	case ESE_EF100_DP_GZ_RX_MAX_RUNT:
+		/* Driver doesn't look at L2_STATUS:LEN_ERR bit, so we don't
+		 * care whether it indicates runt or overlength for any given
+		 * packet, so we don't care about this parameter.
+		 */
+		return 0;
+	default:
+		/* Host interface says "Drivers should ignore design parameters
+		 * that they do not recognise."
+		 */
+		netif_dbg(efx, probe, efx->net_dev,
+			  "Ignoring unrecognised design parameter %u\n",
+			  reader->type);
+		return 0;
+	}
+}
+
+static int ef100_check_design_params(struct efx_nic *efx)
+{
+	struct ef100_tlv_state reader = {};
+	u32 total_len, offset = 0;
+	efx_dword_t reg;
+	int rc = 0, i;
+	u32 data;
+
+	efx_readd(efx, &reg, ER_GZ_PARAMS_TLV_LEN);
+	total_len = EFX_DWORD_FIELD(reg, EFX_DWORD_0);
+	netif_dbg(efx, probe, efx->net_dev, "%u bytes of design parameters\n",
+		  total_len);
+	while (offset < total_len) {
+		efx_readd(efx, &reg, ER_GZ_PARAMS_TLV + offset);
+		data = EFX_DWORD_FIELD(reg, EFX_DWORD_0);
+		for (i = 0; i < sizeof(data); i++) {
+			rc = ef100_tlv_feed(&reader, data);
+			/* Got a complete value? */
+			if (!rc && reader.state == EF100_TLV_TYPE)
+				rc = ef100_process_design_param(efx, &reader);
+			if (rc)
+				goto out;
+			data >>= 8;
+			offset++;
+		}
+	}
+	/* Check we didn't end halfway through a TLV entry, which could either
+	 * mean that the TLV stream is truncated or just that it's corrupted
+	 * and our state machine is out of sync.
+	 */
+	if (reader.state != EF100_TLV_TYPE) {
+		if (reader.state == EF100_TLV_TYPE_CONT)
+			netif_err(efx, probe, efx->net_dev,
+				  "truncated design parameter (incomplete type %u)\n",
+				  reader.type);
+		else
+			netif_err(efx, probe, efx->net_dev,
+				  "truncated design parameter %u\n",
+				  reader.type);
+		rc = -EIO;
+	}
+out:
+	return rc;
+}
+
 /*	NIC probe and remove
  */
 static int ef100_probe_main(struct efx_nic *efx)
@@ -536,6 +738,20 @@ static int ef100_probe_main(struct efx_nic *efx)
 	net_dev->features |= efx->type->offload_features;
 	net_dev->hw_features |= efx->type->offload_features;
 
+	/* Populate design-parameter defaults */
+	nic_data->tso_max_hdr_len = ESE_EF100_DP_GZ_TSO_MAX_HDR_LEN_DEFAULT;
+	nic_data->tso_max_frames = ESE_EF100_DP_GZ_TSO_MAX_NUM_FRAMES_DEFAULT;
+	nic_data->tso_max_payload_num_segs = ESE_EF100_DP_GZ_TSO_MAX_PAYLOAD_NUM_SEGS_DEFAULT;
+	nic_data->tso_max_payload_len = ESE_EF100_DP_GZ_TSO_MAX_PAYLOAD_LEN_DEFAULT;
+	net_dev->gso_max_segs = ESE_EF100_DP_GZ_TSO_MAX_HDR_NUM_SEGS_DEFAULT;
+	/* Read design parameters */
+	rc = ef100_check_design_params(efx);
+	if (rc) {
+		netif_err(efx, probe, efx->net_dev,
+			  "Unsupported design parameters\n");
+		goto fail;
+	}
+
 	/* we assume later that we can copy from this buffer in dwords */
 	BUILD_BUG_ON(MCDI_CTL_SDU_LEN_MAX_V2 % 4);
 
diff --git a/drivers/net/ethernet/sfc/ef100_nic.h b/drivers/net/ethernet/sfc/ef100_nic.h
index 6367bbb2c9b3..c8816bc6ae78 100644
--- a/drivers/net/ethernet/sfc/ef100_nic.h
+++ b/drivers/net/ethernet/sfc/ef100_nic.h
@@ -26,6 +26,10 @@ struct ef100_nic_data {
 	u16 warm_boot_count;
 	u8 port_id[ETH_ALEN];
 	DECLARE_BITMAP(evq_phases, EFX_MAX_CHANNELS);
+	u16 tso_max_hdr_len;
+	u16 tso_max_payload_num_segs;
+	u16 tso_max_frames;
+	unsigned int tso_max_payload_len;
 };
 
 #define efx_ef100_has_cap(caps, flag) \

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