linux-kernel - [PATCH 3.2 38/77] AHCI: Fix softreset failed issue of Port Multiplier

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Date:	Thu, 24 Dec 2015 15:37:42 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Xiangliang Yu" <Xiangliang.Yu@....com>,
	"Tejun Heo" <tj@...nel.org>
Subject: [PATCH 3.2 38/77] AHCI: Fix softreset failed issue of Port Multiplier

3.2.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/ata/libahci.c | 9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -1226,6 +1226,15 @@ static int ahci_exec_polled_cmd(struct a
 	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);
 

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