From: David Milburn <dmilburn@redhat.com>
Date: Tue, 14 Nov 2017 16:17:25 -0600
Subject: [PATCH] libata: sata_down_spd_limit should return if driver has not
recorded sstatus speed
Git-commit: 2dc0b46b5ea30f169b0b272253ea846a5a281731
Patch-Mainline: v4.15-rc4
References: bsc#1079088
During hotplug, it is possible for 6Gbps link speed to be limited all
the way down to 1.5 Gbps which may lead to a slower link speed when
drive is re-connected.
This behavior has been seen on a Intel Lewisburg SATA controller
(8086:a1d2) with HGST HUH728080ALE600 drive where SATA link speed was
limited to 1.5 Gbps and when re-connected the link came up 3.0 Gbps.
This patch was retested on above configuration and showed the
hotplugged link to come back online at max speed (6Gbps). I did not
see the downgrade when testing on Intel C600/X79, but retested patched
linux-4.14-rc5 kernel and didn't see any side effects from this
change. Also, successfully retested hotplug on port multiplier 3Gbps
link.
tj: Minor comment updates.
Signed-off-by: David Milburn <dmilburn@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Hannes Reinecke <hare@suse.com>
---
drivers/ata/libata-core.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 2a882929de4a..8193b38a1cae 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3082,13 +3082,19 @@ int sata_down_spd_limit(struct ata_link *link, u32 spd_limit)
bit = fls(mask) - 1;
mask &= ~(1 << bit);
- /* Mask off all speeds higher than or equal to the current
- * one. Force 1.5Gbps if current SPD is not available.
+ /*
+ * Mask off all speeds higher than or equal to the current one. At
+ * this point, if current SPD is not available and we previously
+ * recorded the link speed from SStatus, the driver has already
+ * masked off the highest bit so mask should already be 1 or 0.
+ * Otherwise, we should not force 1.5Gbps on a link where we have
+ * not previously recorded speed from SStatus. Just return in this
+ * case.
*/
if (spd > 1)
mask &= (1 << (spd - 1)) - 1;
else
- mask &= 1;
+ return -EINVAL;
/* were we already at the bottom? */
if (!mask)
--
2.12.3