linux-kernel - [PATCH -mm 2/8] AHCI: Speed-up resume

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Date:	Thu, 10 Jul 2008 01:58:48 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@...e.cz>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Zhang Rui <rui.zhang@...el.com>,
	Jeff Garzik <jeff@...zik.org>
Subject: [PATCH -mm 2/8] AHCI: Speed-up resume

From: Zhang Rui <rui.zhang@...el.com>
Subject: AHCI: Speed-up resume

During resume, sleep 1 second to wait for the HBA reset
to finish is a waste of time.

According to the AHCI 1.2 spec,
We should poll the HOST_CTL register,
and return error if the host reset is not
finished within 1 second.

Test results show that the HBA reset can be done quickly(in usecs).
And this patch may save nearly 1 second during resume.

Signed-off-by: Zhang Rui <rui.zhang@...el.com>
Acked-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
--
 drivers/ata/ahci.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Index: linux-next/drivers/ata/ahci.c
===================================================================
--- linux-next.orig/drivers/ata/ahci.c
+++ linux-next/drivers/ata/ahci.c
@@ -1142,12 +1142,15 @@ static int ahci_reset_controller(struct 
 			readl(mmio + HOST_CTL); /* flush */
 		}
 
-		/* reset must complete within 1 second, or
+		/*
+		 * to perform host reset, OS should set HOST_RESET
+		 * and poll until this bit is read to be "0".
+		 * reset must complete within 1 second, or
 		 * the hardware should be considered fried.
 		 */
-		ssleep(1);
+		tmp = ata_wait_register(mmio + HOST_CTL, HOST_RESET,
+					HOST_RESET, 10, 1000);
 
-		tmp = readl(mmio + HOST_CTL);
 		if (tmp & HOST_RESET) {
 			dev_printk(KERN_ERR, host->dev,
 				   "controller reset failed (0x%x)\n", tmp);

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