[3.16.y-ckt stable] Patch "AHCI: Fix softreset failed issue of Port Multiplier" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    AHCI: Fix softreset failed issue of Port Multiplier

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt23.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

---8<------------------------------------------------------------

>From 2368f9abd27a21b2f7fc6c5901f0246b2ab8efc5 Mon Sep 17 00:00:00 2001
From: Xiangliang Yu <Xiangliang.Yu at amd.com>
Date: Thu, 26 Nov 2015 20:27:02 +0800
Subject: AHCI: Fix softreset failed issue of Port Multiplier

commit 023113d24ef9e1d2b44cb2446872b17e2b01d8b1 upstream.

Current code doesn't update port value of Port Multiplier(PM) when
sending FIS of softreset to device, command will fail if FBS is
enabled.

There are two ways to fix the issue: the first is to disable FBS
before sending softreset command to PM device and the second is
to update port value of PM when sending command.

For the first way, i can't find any related rule in AHCI Spec. The
second way can avoid disabling FBS and has better performance.

Signed-off-by: Xiangliang Yu <Xiangliang.Yu at amd.com>
Signed-off-by: Tejun Heo <tj at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/ata/libahci.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 86c3c24b835f..a0bfdcfafd92 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -1271,6 +1271,15 @@ static int ahci_exec_polled_cmd(struct ata_port *ap, int pmp,
 	ata_tf_to_fis(tf, pmp, is_cmd, fis);
 	ahci_fill_cmd_slot(pp, 0, cmd_fis_len | flags | (pmp << 12));

+	/* set port value for softreset of Port Multiplier */
+	if (pp->fbs_enabled && pp->fbs_last_dev != pmp) {
+		tmp = readl(port_mmio + PORT_FBS);
+		tmp &= ~(PORT_FBS_DEV_MASK | PORT_FBS_DEC);
+		tmp |= pmp << PORT_FBS_DEV_OFFSET;
+		writel(tmp, port_mmio + PORT_FBS);
+		pp->fbs_last_dev = pmp;
+	}
+
 	/* issue & wait */
 	writel(1, port_mmio + PORT_CMD_ISSUE);