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From: Andrew Rybchenko <arybchenko@solarflare.com>
To: <dev@dpdk.org>
Cc: Andrew Rybchenko <Andrew.Rybchenko@oktetlabs.ru>
Subject: [dpdk-dev] [PATCH 20/53] net/sfc/base: clarify meaning of Rx desc lbits in PS mode
Date: Thu, 16 Nov 2017 08:04:08 +0000	[thread overview]
Message-ID: <1510819481-6809-21-git-send-email-arybchenko@solarflare.com> (raw)
In-Reply-To: <1510819481-6809-1-git-send-email-arybchenko@solarflare.com>

From: Andrew Rybchenko <Andrew.Rybchenko@oktetlabs.ru>

There is no point to add mask plus one before mask applying since it
still does not help to avoid overflow on subtract. Modulo mask
arithmetic works perfectly for unsigned integers of the same type.

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
---
 drivers/net/sfc/base/ef10_ev.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/net/sfc/base/ef10_ev.c b/drivers/net/sfc/base/ef10_ev.c
index eb9ec75..9ed22f8 100644
--- a/drivers/net/sfc/base/ef10_ev.c
+++ b/drivers/net/sfc/base/ef10_ev.c
@@ -774,7 +774,7 @@ ef10_ev_rx_packed_stream(
 	__in_opt	void *arg)
 {
 	uint32_t label;
-	uint32_t next_read_lbits;
+	uint32_t pkt_count_lbits;
 	uint16_t flags;
 	boolean_t should_abort;
 	efx_evq_rxq_state_t *eersp;
@@ -782,15 +782,22 @@ ef10_ev_rx_packed_stream(
 	unsigned int current_id;
 	boolean_t new_buffer;
 
-	next_read_lbits = EFX_QWORD_FIELD(*eqp, ESF_DZ_RX_DSC_PTR_LBITS);
+	pkt_count_lbits = EFX_QWORD_FIELD(*eqp, ESF_DZ_RX_DSC_PTR_LBITS);
 	label = EFX_QWORD_FIELD(*eqp, ESF_DZ_RX_QLABEL);
 	new_buffer = EFX_QWORD_FIELD(*eqp, ESF_DZ_RX_EV_ROTATE);
 
 	flags = 0;
 
 	eersp = &eep->ee_rxq_state[label];
-	pkt_count = (EFX_MASK32(ESF_DZ_RX_DSC_PTR_LBITS) + 1 +
-	    next_read_lbits - eersp->eers_rx_stream_npackets) &
+
+	/*
+	 * RX_DSC_PTR_LBITS has least significant bits of the global
+	 * (not per-buffer) packet counter. It is guaranteed that
+	 * maximum number of completed packets fits in lbits-mask.
+	 * So, modulo lbits-mask arithmetic should be used to calculate
+	 * packet counter increment.
+	 */
+	pkt_count = (pkt_count_lbits - eersp->eers_rx_stream_npackets) &
 	    EFX_MASK32(ESF_DZ_RX_DSC_PTR_LBITS);
 	eersp->eers_rx_stream_npackets += pkt_count;
 
-- 
2.7.4

  parent reply	other threads:[~2017-11-16  8:05 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-16  8:03 [dpdk-dev] [PATCH 00/53] net/sfc: base driver update Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 01/53] net/sfc/base: copy new header from firmwaresrc Andrew Rybchenko
2017-11-27 19:58   ` Ferruh Yigit
2017-11-29  9:49     ` Andrew Rybchenko
2017-11-27 19:58   ` Ferruh Yigit
2017-11-16  8:03 ` [dpdk-dev] [PATCH 02/53] net/sfc/base: do not use Tx desc push with TSO descriptors Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 03/53] net/sfc/base: fix result code in MCDI NVRAM update finish Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 04/53] net/sfc/base: simplify verify result handling Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 05/53] net/sfc/base: report verify result from RW finish callback Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 06/53] net/sfc/base: extend NVRAM RW finish to return verify result Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 07/53] net/sfc/base: rename firmware update verify result cap field Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 08/53] net/sfc/base: simplify NVRAM type to partition mappings Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 09/53] net/sfc/base: check NVRAM locking by partition ID Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 10/53] net/sfc/base: report correct partition write chunk size Andrew Rybchenko
2017-11-16  8:03 ` [dpdk-dev] [PATCH 11/53] net/sfc/base: fix check in NVRAM validate Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 12/53] net/sfc/base: precheck and verify flash writes Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 13/53] net/sfc/base: remove duplicate NVRAM asserts Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 14/53] net/sfc/base: quieten get version methods Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 15/53] net/sfc/base: fix PreFAST issues Andrew Rybchenko
2017-11-27 19:58   ` [dpdk-dev] [dpdk-stable] " Ferruh Yigit
2017-11-28 11:49     ` Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 16/53] net/sfc/base: add support for MUM/SUC firmware partitions Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 17/53] net/sfc/base: improve PS credits push function name Andrew Rybchenko
2017-11-27 19:59   ` Ferruh Yigit
2017-11-28  9:20     ` Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 18/53] net/sfc/base: improve RxQ label init prototype Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 19/53] net/sfc/base: add description of the PS packets layout Andrew Rybchenko
2017-11-16  8:04 ` Andrew Rybchenko [this message]
2017-11-16  8:04 ` [dpdk-dev] [PATCH 21/53] net/sfc/base: optimize credits overflow check Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 22/53] net/sfc/base: provide simple access to RxQ state in EvQ Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 23/53] net/sfc/base: enforce packed stream fake buffer size Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 24/53] net/sfc/base: more accurately calculate number of PS credits Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 25/53] net/sfc/base: make MAC naming consistent with other modules Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 26/53] net/sfc/base: support inner checksum offload on transmit Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 27/53] net/sfc/base: use MCDIv2 for requests with too long response Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 28/53] net/sfc/base: ignore error in completion event on MCDIv2 HW Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 29/53] net/sfc/base: request info about outer frame in Rx events Andrew Rybchenko
2017-11-27 19:57   ` Ferruh Yigit
2017-11-28 10:48     ` Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 30/53] net/sfc/base: remove assertion on no longer used define Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 31/53] net/sfc/base: improve names for EVQ descriptor counts Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 32/53] net/sfc/base: improve names for RXQ " Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 33/53] net/sfc/base: improve names for TXQ " Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 34/53] net/sfc/base: fix build issue with PHY LED control enabled Andrew Rybchenko
2017-11-27 19:59   ` [dpdk-dev] [dpdk-stable] " Ferruh Yigit
2017-11-16  8:04 ` [dpdk-dev] [PATCH 35/53] net/sfc/base: move Siena-specific defs to right header Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 36/53] net/sfc/base: run mkconfig.py to add a new sensors Andrew Rybchenko
2017-11-27 19:58   ` Ferruh Yigit
2017-11-28 12:01     ` Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 37/53] net/sfc/base: add support for " Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 38/53] net/sfc/base: remove unused defined for WPTR alignment Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 39/53] net/sfc/base: cstyle fixes Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 40/53] net/sfc/base: allow to use PHY stats on Huntington/Medford Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 41/53] net/sfc/base: fix diagnostics support build without Siena Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 42/53] net/sfc/base: fix probes in licensing support Andrew Rybchenko
2017-11-27 19:58   ` [dpdk-dev] [dpdk-stable] " Ferruh Yigit
2017-11-28 10:17     ` Andrew Rybchenko
2017-11-28 21:38       ` Ferruh Yigit
2017-11-29  9:51         ` Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 43/53] net/sfc/base: fix warnings from VS2015 C compiler (C4310) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 44/53] net/sfc/base: fix warnings from VS2015 C compiler (C4244) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 45/53] net/sfc/base: fix warnings from VS2015 C compiler (C4245) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 46/53] net/sfc/base: fix warnings from VS2015 C compiler (C4100) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 47/53] net/sfc/base: fix warnings from VS2015 C compiler (C4189) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 48/53] net/sfc/base: fix warnings from VS2015 C compiler (C4057) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 49/53] net/sfc/base: fix warnings from VS2015 C compiler (C4214) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 50/53] net/sfc/base: remove obsolete check for pre-Siena hardware Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 51/53] net/sfc/base: expand on comment on number of queues field Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 52/53] net/sfc/base: fix PreFAST static analysis warning (C6001) Andrew Rybchenko
2017-11-16  8:04 ` [dpdk-dev] [PATCH 53/53] net/sfc/base: move BIU test code into Siena-specific file Andrew Rybchenko
2017-11-27 19:59 ` [dpdk-dev] [PATCH 00/53] net/sfc: base driver update Ferruh Yigit

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