linux-kernel - [PATCH 4.2.y-ckt 133/305] AHCI: Fix softreset failed issue of Port Multiplier

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Message-Id: <1452902519-2754-134-git-send-email-kamal@canonical.com>
Date:	Fri, 15 Jan 2016 15:59:07 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Xiangliang Yu <Xiangliang.Yu@....com>, Tejun Heo <tj@...nel.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 133/305] AHCI: Fix softreset failed issue of Port Multiplier

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

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

From: Xiangliang Yu <Xiangliang.Yu@....com>

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@....com>
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/ata/libahci.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index d256a66..98c482a 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -1266,6 +1266,15 @@ 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);
 
-- 
1.9.1