linux-kernel - [PATCH] IB/ehca: Fix static rate if path faster than link

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Message-Id: <200711281446.29085.fenkes@de.ibm.com>
Date:	Wed, 28 Nov 2007 15:46:28 +0200
From:	Joachim Fenkes <fenkes@...ibm.com>
To:	"LinuxPPC-Dev" <linuxppc-dev@...abs.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"OF-General" <general@...ts.openfabrics.org>,
	Roland Dreier <rolandd@...co.com>,
	"OF-EWG" <ewg@...ts.openfabrics.org>
Cc:	"Hoang-Nam Nguyen" <hnguyen@...ibm.com>,
	Christoph Raisch <raisch@...ibm.com>,
	Stefan Roscher <stefan.roscher@...ibm.com>,
	Marcus Eder <meder@...ibm.com>
Subject: [PATCH] IB/ehca: Fix static rate if path faster than link

The formula would yield -1 for this, which is wrong in a bad way (max
throttling). Clamp to 0, which is the correct value.

Signed-off-by: Joachim Fenkes <fenkes@...ibm.com>
---

This fixes another regression introduced in rc3.
Please review and apply for 2.6.24-rc4. Thanks!

 drivers/infiniband/hw/ehca/ehca_av.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/ehca/ehca_av.c b/drivers/infiniband/hw/ehca/ehca_av.c
index 453eb99..f7782c8 100644
--- a/drivers/infiniband/hw/ehca/ehca_av.c
+++ b/drivers/infiniband/hw/ehca/ehca_av.c
@@ -76,8 +76,12 @@ int ehca_calc_ipd(struct ehca_shca *shca, int port,
 
 	link = ib_width_enum_to_int(pa.active_width) * pa.active_speed;
 
-	/* IPD = round((link / path) - 1) */
-	*ipd = ((link + (path >> 1)) / path) - 1;
+	if (path >= link)
+		/* no need to throttle if path faster than link */
+		*ipd = 0;
+	else
+		/* IPD = round((link / path) - 1) */
+		*ipd = ((link + (path >> 1)) / path) - 1;
 
 	return 0;
 }
-- 
1.5.2



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