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Date: Fri, 04 Jul 2008 13:32:17 +0800
From: Zhang Rui <rui.zhang@...el.com>
To: Tejun Heo <tj@...nel.org>
Cc: linux-pm <linux-pm@...ts.linux-foundation.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [RFC PATCH] AHCI: speed up resume
On Fri, 2008-07-04 at 10:48 +0800, Tejun Heo wrote:
> Hello, Zhang.
>
> Zhang Rui wrote:
> > During S3 resume, AHCI driver sleeps 1 second to wait for the HBA
> reset
> > to finish. This is luxurious, :)
> >
> > 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>
> > --
> > drivers/ata/ahci.c | 17 ++++++++++++++---
> > 1 file changed, 14 insertions(+), 3 deletions(-)
> >
> > Index: linux-2.6/drivers/ata/ahci.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/ata/ahci.c 2007-05-03 11:06:33.000000000
> +0800
> > +++ linux-2.6/drivers/ata/ahci.c 2008-07-02 16:25:54.000000000
> +0800
> > @@ -1073,18 +1073,29 @@
> >
> > /* global controller reset */
> > if (!ahci_skip_host_reset) {
> > + int delay = msecs_to_jiffies(1000);
> > + int timeout;
> > +
> > tmp = readl(mmio + HOST_CTL);
> > if ((tmp & HOST_RESET) == 0) {
> > writel(tmp | HOST_RESET, mmio + HOST_CTL);
> > 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);
> > + timeout = jiffies + delay;
> > + while (jiffies < timeout) {
> > + tmp = readl(mmio + HOST_CTL);
> > + if (!(tmp & HOST_RESET))
> > + break;
> > + cpu_relax();
> > + }
>
> Looks good in principle. Just two things...
>
> 1. Please don't busy-loop. e.g. No one would notice 10ms delay
> between
> polls.
>
> 2. Please use ata_wait_register().
>
Thanks for review, refreshed patch attached. :)
From: Zhang Rui <rui.zhang@...el.com>
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>
--
drivers/ata/ahci.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
Index: linux-2.6/drivers/ata/ahci.c
===================================================================
--- linux-2.6.orig/drivers/ata/ahci.c 2008-07-04 09:49:05.000000000 +0800
+++ linux-2.6/drivers/ata/ahci.c 2008-07-04 11:31:30.000000000 +0800
@@ -1079,12 +1079,15 @@
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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