From 2dc0b46b5ea30f169b0b272253ea846a5a281731 Mon Sep 17 00:00:00 2001 From: David Milburn 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 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 Signed-off-by: Tejun Heo --- 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)